Linq union null My current linq points to a view that does the union for me but I want to know how to do it right in linq. MChaker Union in linq entity framework. So when I try to convert "results" to a List, I get {"The cast to value type 'System. AsEnumerable(). size }; @klekmek, apply the Where clause to each quizType1Attempts and quizType2Attempts. What In SQL: UNION is a set operator and involves checking for (and suppressing) duplicate rows; Duplicate rows are defined as not being distinct; Distinct (values or rows) is defined as: Two values are said to be not distinct if either: both are the null value, or they compare equal according to Subclause 8. id)); Update. 3. Select[TSource,TResult](IEnumerable`1 source, Func`2 selector) As the source parameter in your LINQ query (var nCounts = from sale in sal) is 'sal', I suppose the list named 'sal' might be null. Union(people2), the outcome is the same. var dset = from s in db. C# Union two lists of objects: 0. 1. Commented Feb 27, 2015 at 8:51 C# LINQ GroupBy NULL Values. Union(containers2. ParentBranchID into g from sc in g. userid FROM ltable AS l LEFT JOIN rtable AS r ON l. AsNotNull(). I want to sort on the basis of this property using LINQ with var sorted_items = firstPart. HandheldAssets join a in db. REGIONS on s. Visible}) . Where(a => a. ItemId == v. I realise that in T-SQL I'd have to use the "IS NULL" operator, but how can I select the rows I want in Linq? I'd like an elegant way to concatenate several columns together using LINQ, but using the + operator or concat() when any of the columns are NULL results in NULL for the value after concatenation. What does a "null-query" mean to you? If it means "no rows" then just don't Union it. Linq: var recs=from m in MASTER from c in child. Generic. var message = from a in _Message. 4. GroupBy(x => x. EMPLOYE on aff. Id or quizType2Attempt. STATES on s. Colunm WHERE tbl. Column = tbls2. Viewed 857 times I am looking for a LINQ method that might already be there. The UnionBy() method takes two sequences and returns a set union of them based on a specified key selector function. Ask Question Asked 12 years, 2 months ago. SomeTable. Using union on two lists is not working as expected. ToList() . ActiveImages on image. You can generate a dummy column though to bypass. If it means "all rows" you don't need to union because you can just take the underlying, unfiltered query. 1) Using LINQ Union() method with sequences of numbers. Per LINQ - Full Outer Join, the easiest way to perform a full outer join is to union two left joins. When the object returned by this method is enumerated, UnionBy enumerates first and second in that Simply put, Union returns the union of the two sequences – all items that are in either input sequence. Then, use it in the same way, i. x. linq union of two lists. FirstName. Count() > 1 select g) . UserId)). ToList()); Where<T>() will return IEnumerable<T>, which will be some subset of the original set. Union(people1) rather than people1. Union<StoreAnalyticOrders>(IQueryable<StoreAnalyticOrders>) requires a receiver of Type IQueryable<StoreAnalyticOrders> This will iterate over query2, and for each item it uses SingleOrDefault to find the item in query1 where the first elements of the items match, or null. How to return null in a GroupBy statement when one of the values in the non-key column contains null? 3. LINQ Union() method examples. With both extensions, one for strings, one I have a 2 lists that contain BreadCrumbItem object: public BreadcrumbItem() { this. If I do a . LINQ Union and Distinct. ParallelQuery, System. Make some List Union in C#. How to perform Union using Linq as i performed in Mysql query. NumLot join emp in entBoum. R# to be sure in the output type and not have a warning for a possible null reference exception (for e. filename, image. Union(l2, comparer). Union lists by content. I Know I could write a select of if else but wanted to know if there is a slicker Linq way!? //j C# Linq Union Returning Null. var finalList = NewCustomers. Union(emptyPoints). However, some LINQ providers have difficulty running CLR methods as part of the query. As of now I have a couple of linq queries to do this for me, but I am wondering if this could be simplified somehow - in the initial parent query if Parent_ID_FK is int? then you can use the property. MARKID=M. ParentId != l1. Alternatively: As you want to use dynamic s, you can do the same with dynamics, but the individual elements need to be dynamic, not the result variable, so if you want to I had this issue now, and neat SQL is a must and got it working in a very optimised way. Include() should be using a LEFT JOIN which does exactly what you're asking for: "I would like to get all Persons, and if the Child is not null, I want to Include it". Sum(z => z. ToList(). Name into g where g. DefaultIfEmpty() wher b. Union two lists together in C#. public static class Extension { public static IEnumerable<T> WhereNotNull<T>(this Summary: in this tutorial, you will learn how to use the LINQ UnionBy() method to create a union of two sequences based on a key selector function. Commented May 11, 2011 at 19:49. MyColumn == null); This does not select any rows from the table, even though there are many rows where "MyColumn is null"? I need to select the rows where MyColumn contains null. AssetID, Status = xx. So you could do. var alerts = from a in dc. Apparently, you are even triggering a bug doing that causing a NullReferenceException. Select(x => 'System. Union of two lists in LINQ not working. Union(list1. 2. The method has an overload to pass in your comparer. DefaultIfEmpty() join v in db. BranchID, v => v. Linq Union does perform as you want it to. But the argument you pass is of type IEnumerable<Schedule>, and it can't translate that into a query. I can't figure out how to union a row for the null,'All' values. The immediate return value is an object that stores all the information that is required to perform the action. PartnerInt == partnerInt && a. g. FirstName != null && x. It returns a new collection If comparer is null, the default equality comparer, Default, is used to compare values. StatusUpdates where s. After that I'm trying to apply sorting to the combined collection by calling OrderBy on a field that is common to the collections. ListOfLongs); I needed an implementation on Union that compares a property of an object, rather the objects themselves. return new List<string> { newItem }. I came up with the following: public static IEnumerable<TSource> UnionBy<TSource, TKey>( this IEnumerable<TSource> first, IEnumerable<TSource> second, Func<TSource, TKey> keySelector, IEqualityComparer<TKey> keyComparer = null) { You should be able to select from your first query instead of the image table again. Hot Network Questions Momentum measurement and uncertainity principle In the result I need distinct list of containers, but if there is one of items is null it throws exception. SingleOrDefault(); // myDate => ((DateTime?)null) That is probably not what you want, you want some value when it is null, then you should use either the coalesce operator of C# 3. Linq to combine collections, removing duplicates. One contains good values (Let's call it "Good"), the other default values (Mr. Url = string. DefaultIfEmpty() where subimage. The . I want the Intersect of the Union between Good and Default, and Default. Obviously, if you forget to filter quizType2Attempts for null values, you'll get an exception when the predicate in the Select clause for quizType2Attempts tries to derefence either quizType2Attempt. RequestTypes on g. NO you can't. Is it possible to Union starting from an empty var? 1. 24. ToList(); Union works fine, but the problem is it is checking each column and removes some of the rows that I want. BranchName); Getting err Cannot compare elements of In SQL you can run a ISNULL(null,'') how would you do this in a linq query? I have a join in this query: var hht = from x in db. NET and I know that Union normally works ByRef but in VB, Strings are generally processed as if they were primitive datatypes. Try it online You have changed the name of the property in the second anonymous type and therefore the compiler will construct two distinct types in your query. It ignores null values in the source sequence. It requires at least two collections to perform the merge operation, but that merged collection holds only the distinct LINQ Union operator is used for finding unique elements between two sequences (Collections). DataTable DT=new DataTable(); DT = PinDicDAO. 17. How can I handle null checking here avoiding multiple if/else statements? I've tried: containers = containers1. Follow edited Jan 21, 2015 at 0:47. Union. OfType<HappyUser>() select u; I'm not quite sure about the use case. Union(p2). userid WHERE l. Examples. B. Linq Union do not work. int[] ints1 = { 5, 3, 9, 7, 5, 9, 3, 7 }; int[] ints2 = { 8, 3, 6, 4, 4, 9, 1, 0 }; // Get the set union of the items in the two arrays. IEnumerable)' has some invalid arguments Instance argument: cannot convert from 'System. DevName into DevInfo from aa in DevInfo. ApplicationID, ApplicationName = d. However, the last time I saw a colleague use the Union to combine dynamic queries. LINQ Union with duplicates. RequestTy If comparer is null, the default equality comparer, Default, is used to compare values. DisplayText,ReviewStepID = null }) . name == y. ToList(); linq union of two lists. I am trying to merge two lists using list. Remove duplicates while merging lists using Union in LINQ. Here’s the syntax of the UnionBy EDIT: Ok I found why the int. Select<T, TResult>() will return IEnumerable<TResult>, some set of new objects selected, based on the old set of objects and the function provided (which accepts an item of type T). Select(y => y. Part of first query looks like this: var query1 = from contract in ContractRepo. first order by ascending null / not nul; The problem is with running Where() on null instance. Union(from u in result. However, when we apply aggregate i. Custom Union in Linq to Entities. Dim union = store1. net-core; entity-framework-core; Share. Online }; Now you want to get person's related post code and you don't know input person is null or not: var postCode = // this gives address or null, if either person is null or its address person. c#. Linq union two tables where on has an extra column. "} Is this Linq-To-Objects or Linq-To-Entities (or any other DB-driven LINQ provider)? If it's translated to a sql query you cannot guarantee the order without an explicit OrderBy. The problem is that the DB providers try to move and compile the LINQ query as a database query, to prevent pulling all of the objects across the wire. FirstName?. : myClass. Let’s explore some approaches to avoid these issues and keep Summary: in this tutorial, you will learn how to use the LINQ Union() method to produce the set union of two sequences. ToList();. NET Core LINQ 2 SQL and EF do not support queries pulling from multiple DB contexts. OrderBy(x => x. Int32' failed because the materialized value is null. Ask Question Asked 13 years, 4 months ago. Union() should never return null. Items select new VotedItem { ItemId = i. fruitType equals dapple. However, under . Something like: var query = from image in imageUnion join active in dc. . 2, "<comparison predicate>". The following code example demonstrates how to use Union<TSource>(IQueryable<TSource>, IEnumerable<TSource>) to obtain the set union of two sequences. To get the UNION to work with the different column names I have to give the other column NULL so that it doesn't ignore it and not include it in the query. Union(thirdPart). Entity Framework and Union Statement. userid = r. C# Linq Union Returning Null. If row in (T) reference You can use System. COMBINE_OR_WHATEVER(); I am taking a union of two lists using Linq to Sql. NumLot equals aff. Union two list by property. c#; linq; How to assign empty string if the value is null in linq query? 1. Union(secondPart). Union(y) is the same as x. ToList() all row will be fetched into memory and then the filtering will happen This question is overlaps a lot with Is there a convenient way to filter a sequence of C# 8. ItemNumber, SUM(a. Just use the same type as MyProperty and it won't filter out anything else. AssetID equals a. 6. Votes where b. Title = string. ToList(); This will essentially resolve the Name property to null if MyOtherObject is null, which will fail the comparison with "Name". Where(r => (r. Users . SUM on same field in collection using LINQ it calculates/returns 0 for null. 20. PostCode); First, Union() is found in System. Simplest way to form a union of two lists. How to use C# LINQ Union to get the Union of Custom list1 with list2. Update: With . This method is implemented by using deferred execution. userid, r. filename equals active. PlanCompiler. address in memory). 1 Performing a union in LINQ Union isn't a member of list, but is an extension on IEnumerable - part of Linq. Select(p => I think frenchie wants a list of MyModel back instead of just the TheUniqueID. REGIONCODE equals w. The Union method does do what you want, as does the Concat method, but both are LAZY evaluations, and have the requirement the parameters be non-null. Users select u; var happyUsers = from u in db. COUNTRies on s. Hot Network Questions System. This is expecially true of some database providers. ItemId, Points = (from v in Db. Where(l1 => list2. In people2, Jennifer, Alton, and Adam are duplicated in people1. OfType<T>(); Your problem is that your query is being turned entirely into a LINQ-to-SQL query, when what you need is a LINQ-to-SQL query with local manipulation on top of it. ParallelQuery<TSource>, System. var comparer = new CustomFormat(null,0); l1 = l1. The trouble I'm having is that the last item is often null. Union, you're asking the EF to translate the expression into SQL. IOrderedQueryable does not contain a definition for 'Union' and the best extension method overload 'System. It seems like if I try and perform a union with the two, if the second argument is null it will throw an ArgumentNullException. This is the working query I currently have: var q = db. Introduction to the LINQ UnionBy() method. UserID == forUser. Name == "Name"). Union, you're asking LINQ to Objects to do the whole thing in memory, which works fine, albeit perhaps slower. Using Union and Contains in LINQ. Select(x => x). So if a single WorkOrder record had both the PrimaryWorker and SecondaryWorker field populated I would I'm using VB . We use integer arrays, but The same Union method can be used on a list of objects as well as simple lists such as ints or strings. EmitFromEnum()); as col. different) objects in concatenated sequences? In your sample code (from question) Linq compares objects by reference (i. MyOtherObject?. { 3 } element is available in both sequences. , null null 2012-04-01 2012-01-01 2011 Skip to main content. How to join table with multiple columns in linq? 0. Data. Union(aCollection); } else { combinedCollection = aCollection; } } Second The exception shouldn't be coming from that line. ToLower(). Union(System. I have an object model that contains a list of longs. BreadcrumbType = BreadcrumbT Is there a LINQ Statement where I can "Union()" all the resulting groups and just return a IEnumerable of my objects? Like IEnumerable<MyObject> Results = (from x in Objects group x by x. So difference is only with applying Distinct. string test = "null"; var listeLotControle = (from x in entBoum. Basically I have an object with 2 different properties, both int and I want to get one list with all values from both properties. Union(store2, New ProductComparer()) For Each product In union Console. REGIONCODE into wlist from w in wlist. While . Regions Union SELECT null,'All' Order by 1,2. I try to: var users = context. Linq extension methods Union (to get the union of two lists) along with Where and All to filter out the items you don't want to include from the first list:. Select(x => x. Modified 7 years, 11 months ago. With LInq-To-Objects Union does it already: "When the object returned by this method is enumerated, Union<TSource> enumerates first and second in that order and yields each element that has linq union of two lists. MyProperty). Union in LinqPad but I can't get it to work and wanted to check my understanding is correct. Once you begin to think in LINQ, which is declarative in nature, you can find many of your tasks to be simpler and more intuitive than the imperative techniques you use x. ZIPCODEs join u in db. But speaking generally, I agree that it's annoying EF limitation, especially the reasoning behind the structurally incompatible initializations requirement, which forces us to use an ugly workaround I'm going to propose you. CoreQuery. Column2 IS NULL UNION SELECT * FROM dbo. We could execute the union as people2. "Default"). public class ProductView { public int Id { get; set; } public bool Active { get; set; } public string Name { get; set; } public int ProductTypeId { get; set; } public int UserCount { get; set; } } void Main() { var product = Products. Id); } } Update. Contains(searchString) or. As a rule you should avoid null values for collections or sequences, just use an empty collection instead. This is, of course, assuming this is LINQ to Object as there is no tags that says otherwise. userid = l. LINQ Union two lists that have same ID but different types. HasValue instead of checking for null. Id))); But please note that Union will use the Equals method of the class to determine if two items match (which by //a list of Nullable<DateTime> with exactly 1 item var listOfDates = new DateTime?[] { null }; var myDate = listOfDates. LOT join aff in entBoum. Select(c => new {c. c#; linq; Share. You can perform the union in memory: db1. The following example uses the Union() method to create a union of sequences of integers. As you can see below, we have two lists of people. FirstDate}) From what I understand the QData query options from the URL are applied to the LINQ expression before querying the SQL server. Table2 WHERE Column2 = value Very straight forward. IQueryable' does not contain a definition for 'Union' and the best extension method overload 'System. Following is the sample code: public class SomeDetail { public string SomeValue1 { get; set; } public string SomeValue2 { get; set; } public string SomeDate { get; set; } } public class SomeDetailComparer : IEqualityComparer<SomeDetail> { bool IEqualityComparer<SomeDetail>. Here is what i was trying to do: {ID = t. Collections. day) : null). filename into gj from subimage in gj. filename == null select new { image. The solution is to tell the compiler that you want to use LINQ-to-Objects after processing the query (in other words, change the extension method resolution to look at IEnumerable<T I'm curious about your observation, I can only observe a single check of GetHashCode for each of the items in each list. ScirraUserID) . Modified 6 years, 2 months ago. For example, suppose we have two collections A = { 1, 2, 3 }, and B = { 3, 4, 5 }. where (mapping=>mapping. TheUniqueID == y. Value property. AsEnumerable()) SELECT Id, Number FROM Vehicle UNION SELECT NULL, ContractorVehicleNumber FROM Workers The entity or complex type 'XXXXXXXX' cannot be constructed in a LINQ to Entities query. Maybe someone could point me in right direction. Ensure your input files are correct (e. ToList(); invitations. DefaultIfEmpty() where c. Table2 tbl2 ON tbl. DeleteDate is DateTime in audit change your message to be. net; entity-framework; linq-to-entities; Share. That will allow you to select all of the rows a single time and set the flag if data was matched appropriately: You need to pass an instance of an IEqualityComparer to the Union method. MasterId == m. MARKID OR (S. ToDictionary(k => k. Address) // this gives post code or returns null, // if previous value in chain is null or post code is null . MARKID IS NULL AND M. DocumentNumber, a. Equals(SomeDetail If comparer is null, the default equality comparer, Default, is used to compare values. StringConvert((double) u. I have a table of WorkOrders. Add a comment | 3 Answers Sorted by: Reset to MVC LINQ Union with compare IComparer vs IEqualityComparer. ParallelEnumerable. AccountId == accountId select new { Alert = a, StatusUpdate = (StatusUpdate)null }; var updates = from s in dc. ToList(); But when i try to use it in LINQ. For example: public static void Main(string[] args) { var setA = new[] {3, 4, 5}; var setB = new[] {6, 7, 8}; var result = from a in setA from b in setB let sum = a + b where sum == 10 // Where, I would personally suggest either of the latter options, as they don't require that the LINQ provider is able to optimise away the filter in the case where A is null. ParallelQuery' I am trying to use Linq Union to add additional record into result but Union do not work. When the object returned by this method is enumerated, UnionBy enumerates first and second in that order and yields each element that has not already been C# Linq Union Returning Null. I use this for showing an "All" selecting in a combo box. I have two tables, UserNotifications and GlobalNotifications. OfType<> solution works, the intent is not quite clear there, I suggest this solution that is pretty much the same that the solution in the question, but it allows compiler and e. ToList(); You have made some mistakes in your implementation. Linq, acts upon 2 collections. It helps me to find the solution. AFFECTATION_LOT on x. RequestTypeId equals rt. In a SQL statement you would write: ON S. Table1 tbl INNER JOIN dbo. Viewed 48k times I have two similar queries and need to apply union to them. 9. Users select SqlFunctions. The obvious answer would be to just to perform Null Values: If either of the collections is null, Union will throw an ArgumentNullException. Then the select yields either the item called match from query1, if it is not null, or the current item of query2. When you create new object via new operator, it allocates memory at new LINQ Union between two tables with the same fields and then returned in a collection. IEnumerable<TSource>)' has some invalid arguments How can I As pointed out by others, your LINQ expression is a closure. IQueryable' to 'System. However in LINQ I have something that looks like this: You can use the OfType operator. Sum() } Handle null in LINQ sum expression. The Union() method returns the union of two sequences. I'm using LINQ's Union method to combine two or more collections. (I'd expect most good LINQ providers / databases to be able to do that, but I'd generally avoid specifying a filter when it's not needed. They return either a ConcatIterator or a UnionIterator, and if called I would like to sort the results so that the NULLs show up at the top, then descending by DateTime, e. Concat(OldCustomers) . Take(9)); That applies to Linq-To-Objects as stated here:. If the input is null they throw an exception, and if it's not null the result will either be a sequence of items, or an empty sequence. Concat(currentList. This means your variable selected is captured by the LINQ expression in each iteration of your foreach-loop. e. Hot Network Questions Map or Thread operation for list From what I understand about the where clause in LINQ, it combines elements from two or more sets based on all possible combinations of each element and then applies the criteria. It also has a SecondaryWorker & SecondaryPay field (which can be null). (filter with not null and then apply group by GroupId) union (filter with null and apply group by to primary key). GroupBy(s => new {s. You need to create a MyModelTheUniqueIDComparer class and pass a new instance of it as a second argument into Union:. Tip: Union works on Lists and arrays. How to use union between two different object in linq. e some examples wouldbe nice or if anyone can recommend a good tutorial on UNION ALL in linq. Id == null //Compiler creates a warning because int will never be null, but it works and creates outer left join select new { MasterId = m. Contains("Suspendu") || How to merge these 2 collections? Problem: When an ApplicationID is in listOfPM and listOfPM2, Test2 is null and should be a number. // given: // public T MyProperty { get; } var nonNullItems = list. var result = items. ID, type = "u", date = c. DefaultIfEmpty() select new foo ); //this is a hack and probably not what you would want to use. Resulting Sequence: The result is a first or second is null. Here is the query : LINQ union with optional null second parameter. Modified 12 years, 2 months ago. To fix the issue, look at the code that is using the result of the query abc and see if it is LINQ Union with duplicates. Contains(searchString) == true But I would suggest you to use If the Key equals null, you want all elements of the group. Hot Network Questions I submitted a paper to a conference that I should not be submitting and it was accepted. SOP30300 WHERE SOPNUMBE = '8403017 ' AND XTNDPRCE <> 0 UNION ALL SELECT LAPTODNM AS Consider the following Linq to Sql entity: Suppose we've named the sides of the OneToMany relationship like ChildTables and ParentTables, then the following code should do the job //create data context MyTableDataContext dc = new MyTableDataContext("Your connection string"); //find all children, i. AccountId == accountId select new { Alert = (Alert)null, StatusUpdate = s }; //both are sequences of anonymous It's because of the latter Union, you cannot guarantee order with it. ID,DisplayText = t. Union() requires to have fulfilled exactly the same properties in both queries so I had to assign "Empty" Department object in second query, but I need to have my Department Name empty and it throws me null exception and I have no idea why it should even throw it, it doesnt make sense to me. Then you'll have int values and not int? – J Man /// <para>This method is implemented by using deferred execution. LINQ Union not returning wanted results. I need to Union these two tables together and date order them to retrieve a users notification history. About; Linq OrderByDescending, null first. ListOfLongs. There are two methods to do this: Do your GroupBy for all non-null elements; Concat it with the null elements; Or: Use parameter ResultSelector of the GroupBy to check whether the Key is null or not, and select either only one element, or all elements of the group; Concatenation method Try to use Concat instead of Union, the former should keep the order whereas the latter is a set method which removes duplicates and does not guarantee any order:. – svick. Let's say I have 2 tables: Users and TempUsers. UserNotifications. Why is Linq-to-sql incorrectly generating the union and how can I work around this? I have a class with one string property and it can be null sometimes or it can be a integer number some times or it can be a string . Consequently, here's the problem: Sub Main() Dim . COUNTRYCODE equals u. Entity. Union(invitations. Union(obj) it does mean that this single extension method covers all other cases I might want such a single-item enumeration. The Union method will work with 2 collections of the same type of elements. That would be really odd, since Enumerable. Don't call Union when one of the arguments is null. OddValue) . ) You have multiple options, first is to do an explicit check against null and the other option is to use Null propagation operator. Name) . Thanks a lot. DefaultIfEmpty(/* default value for right */) select new { /* use left and newRight to I am trying to implement LINQ query to Entity Framework with union. Where(e => e != null) . Equals(other. Contains("Libéré") || x. IEnumerable)' has some invalid arguments. l = l. Distinct(). Any known reason for this ? I am checking my input lists are null or not before doing this concat – Sebastian. I wish to run 2 very similar queries & union them so that it will return a Worker Field & Pay field. What's the &quot;best&quot; (taking both speed and readability into account) way to determine if a list is empty? Even if the list is of type IEnumerable&lt;T&gt; and doesn't have a Count property. HandheldDevInfos on x. HasValue ? x. DefaultIfEmpty(). 11. Union Lists using IEqualityComparer. I want to get the combined list of longs of two different instances. EtatLot. Improve this question. ItemId select v. Also to get the actual int value use the . To confirm that, check the SQL that is generated from your LINQ. – Long story short: I have 2 collections of objects. Union(obj. name check. I guess I described the problem incorrectly, let's say we have some value: class Value { String name Int whatever; } and the comparer used performs a x. class MyModelTheUniqueIDComparer : IEqualityComparer<MyModel> { public bool Equals(MyModel x, MyModel y) { return x. When the object returned by this method is enumerated, UnionBy enumerates first and second in that order and yields each element that has not already been Solved it with empty list union: List<int> emptyPoints = new List<int>() { 0 }; from i in Db. Branches on b. Shortly, there is no way to workaround the null enumerable assignment other than not including the I was always using the LinqKit to implement dynamic and cooperative predicates. WriteLine(product. The table has a PrimaryWorker & PrimaryPay field. The easiest and ugliest solution is. Share. Follow edited Nov 27, 2018 at 9:07. But when you use a variable, I'm guessing that LINQ doesn't automatically do that conversion. The query is as follows: UserTest db = new UserTest(); var users = from u in db. So union operator only takes one element in the result. 1 Join and Union with Entity Framework. Is there anything similar to concat() that handles NULL differently, or am I thinking about this in the incorrect way? Any help is appreciated! Linq union on anonymous types Recently in my project, i was trying to do a LINQ union on two anonymous types. 0 or one of the overloads of the How to fix and this would look in LINQ i. Union(List2). (combinedCollection != null) { combinedCollection = combinedCollection. [name] = @p__linq__1 (such as Union) on two collections, or iterating through a List and running a lambda in a ForEach of each item. Id}; Likewise, to avoid null when you expect a list, you can add a 2nd extension as overload from this answer. But as far as an implementation of Union using your comparer, think of it like this . fruitType into apples from apple in apples. I am avoiding sum for null field as following. ApplicationName, Test1 = d. And let's say that sometimes I know I should take the element from the second sequence, because it's whatever field is newer / better than the whatever field of the first sequence. One answer posted there exhibited best performance and was extremely consise, with the relevant coding snippet repeated here for posterity:. IdSelectionType, s. Name, s. Commented May 20, 2016 at 9:13. users. My issue is I have results that looks like this: id | departure | arrival 1 asd NULL 2 asd NULL 3 asd NULL 4 asd NULL 5 NULL efg The property could have actually NULL in database. Union (from rs in -- users that exist in both sides or left only SELECT l. Otherwise they are distinct. How to sum a field on linq that has a where clause which pulls When I attempt to do the union DB-side, I get a null reference exception deep down in System. TotalDays = x. 8. EDIT I have rewritten the LINQ query to this and fixed my error: Here is my original query I masked my issue withgeneric one but this one is also simple return (from b in join firm in _db. Where(v => v. userid IS C# Linq Union Returning Null. OrderByDescending(m => m. So you will want to include the appropriate using-directive. var result = list2. Why can't I Concat or Union results to an empty List? 1. I think you are looking for something like UnionBy. count, Test2 = null }; var listOfPM2 = from d in gbc2 select new i am getting a null exception after trying to navigate to the result. The result sequence has no duplicates in even if one of the input Union is an extension method to merge two collections. var result= (from fruit in fruitTable join dapple in applesIQuery on fruit. Id. Union<TSource>(System. Users. ItemAmount) AS ItemAmount FROM (SELECT SopNumbe AS DocumentNumber, ITEMNMBR AS ItemNumber, XTNDPRCE AS ItemAmount FROM dbo. day. Ask Question Asked 6 years, 2 months ago. ' Get the products from the both arrays ' excluding duplicates. the entities with ParentId set var allChildEntities = Lets say I have this IQueryable variable :. It will never be null. I noticed that I was unable to structure a linq query with a union of two selects, using ANSI syntax. For Report purpose ,During LINQ execution,What is the way to replace null values (Based on Delivery Date) with message "Yet to be delivered" (DateTime is value type). ThenByDescending(x => x. DefaultIfEmpty()); But it doesn't help, the same issue. Hot Network Questions UnionBy<TSource,TKey>(IQueryable<TSource>, IEnumerable<TSource>, Expression<Func<TSource,TKey>>) Produces the set union of two sequences according to a specified key selector function. The same variable is used in each iteration of the foreach, so it I have the following SQL query: SELECT a. Key equals right. When the object returned by this method is enumerated, Union enumerates first and SELECT DISTINCT Area, Region FROM dbo. As of C# 6, you can also use a null conditional operator?. Alerts where a. I need union data from all 3. CustomerID) . Taking union of two lists based on column. How to replace null by "NULL" in a List<string> without foreach loop? 1. UNION from multiple lists. So when you call Queryable. Let’s take some examples of using the LINQ Union() method. Points). * FROM dbo. When you explicitly check for "field == NULL", LINQ probably converts that to "field IS NULL". On the other hand, when you call Enumerable. The following code example demonstrates how to use Union<TSource>(IEnumerable<TSource>, IEnumerable<TSource>) to obtain the union of two Handling null values in LINQ queries can be a common challenge, as it often leads to NullReferenceException errors, which can crash your application. DefaultIfEmpty() join w in db. I know I can combine query syntax selects and Method based selects to bypass this problem, but I SELECT tbl2. This exception could point to the LINQ parameter that is named source: System. WHERE @p__linq__0 IS NULL OR [Extent1]. 0. BranchID equals firm. LastName) . You want to do this on your return: return (p1. userid -- must use union all to match the behavior of full outer join UNION ALL -- users that exist in right only SELECT NULL, r. DefaultIfEmpty() select new { AssetID = x. Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand; OverflowAI GenAI features for Teams; OverflowAPI Train & fine-tune LLMs; Labs The future of collective knowledge sharing; About the company If you want to match rows where the values are both null you should use a statement that checks both of them for null. Basic criteria on union is that column count must match b/w tables. LINQ Union not going into overridden Equals method. Tato metoda se implementuje pomocí odloženého spuštění. Follow edited Apr 14, 2017 at 12:58. static IEnumerable<T> Union<T>(this IEnumerable<T> first, IEnumerable<T> second, IEqualityComparer<T> comparer) { // there's undoubtedly validation hi I have the following code and would like to only make each union if a condition is true. Select(e Linq union all equivalent of sql code. With further understanding of the issues, I think this will take care of it: Since NULL means undefined, you can't say that two null values are equal, since by definition you don't know what they are. Where(c => c. Linq to get a combined list out of lists C#. TheUniqueID; } // If Equals() When I try to Union all the related data in the FeedDTO methods are null; linq; asp. Union on empty Enumerable. Because the integer is a primitive type, the Union() method compares them by values: 'System. CreateDate < startDate && (endDate == null || endDate > The Join method is like a SQL join, where the list are cross referenced based upon a condition, it isn't a string concatenation or Adding to a list. Where(x => x. 0 nullable references, retaining only non-nulls?. . N. ToList(); users. C# - Combine multiple LINQ collections with same properties. GetContractPOVD(). Viewed 44k times 20 . Union A List of Lists Using Linq. UnionBy Linq Implementation. UnionBy<TSource,TKey>(IQueryable<TSource>, IEnumerable<TSource>, Expression<Func<TSource,TKey>>) Produces the set union of two sequences according to a specified key selector function. var listOfPM = from d in gbc select new Tab24PresentationModel { ApplicationID = d. Name & " " & product. Field<string I have a table (T) which has references to 2 additional tables (A,B) (both references are null-able, but there is still one filled in per row). net examples for method syntax, a union example is given. – Jenish Rabadiya. It's to use a left outer join instead of the inner join that LINQ defaults to. Using List1 and List2: var tr = List1. considering a. Users select u. like. Union(TheObject2. LINQ query with Distinct and Union . This is List<StoreItems> does not contain a definition for 'Union' and the best extension method overload Queryable. Union(store2) For Each product In union Console. Union(otherL). C# linq union question. Linq Union Operator. COUNTRYCODE into ulist from u in ulist. If I call ToList() on each part individually, it works; and if I call ToList() on each part and then union those, it works. GetAll() (lots of joins) select new ContractViewModel(){ (lots of fields) Attachments = null } Part of second query: I haven't done the null check but they are trivial. Id). Given this simple class: public class Test { public int Id { get; set;} public int field1 { get; set; } public bool Equals(Test other) { return this. This computes mathematical unions. 93. Union(db2. How Linq selects distinct (i. This extension method, from System. All(l2 => l2. When I write this: var MyCombinedList = TheObject1. one of the lines may contain a space before the newline) var myRows = myContext. ToList(); Here is one approach with Linq. Stack Overflow. userid FROM rtable AS r LEFT JOIN ltable AS l ON r. Subject when the current quizType2Attempt I'm trying to merge 2 lists using "Union" so I get rid of duplicates. DeletedDate == null && g == null select b). Either the result type's generic parameter or the query must use a nullable type. IdEmploye equals emp. Also, whilst in this case, Union and Concat LINQ statements will do the same thing, conceptually, you're doing a Concat, so maybe you should use that function instead :). ToLower()?. STATECODE equals C# Linq Union Returning Null. Hot Network Questions Are there specific limits, of what percentage and above is considered as plagiarism? This will work fine with Linq to Objects. Select(u =&gt; new UserModel LINQ Union operator is used for finding unique elements between two sequences (Collections). IdEmploye where x. @flem They can never be null because that's how Where and SelectMany work. ToString() in LINQtoEF fails, please read this post: Problem with converting int to string in Linq to entities This works on my side : List<string> materialTypes = (from u in result. net documentation has an article on query syntax examples where union is not shown. FirstOrDefault After testing it appears that Linq seems to be "optimizing" out the nulls so it's only returning one null column instead of 3, thus causing a mis-match. Here’s the Use the Union extension method from System. With(x=>x. Union operator will find unique elements in both sequences. This means it's pure and doesn't affect the state of the list, but returns a new Enumeration. A left-join in LINQ (using the extension method syntax) takes the form: var leftJoined = from left in lefts join right in rights on left. Union will compare the instances of Customer object(if IEqualityComparer is not used). myarray . Code) Next ' This code produces the following output: ' ' apple 9 ' orange 4 ' lemon 12 ' Remarks. GetAll() . GeneralRequests join rt in ctx. SELECT *, NULL AS purchaseOrderItemId, NULL AS isOrdered, NULL AS orderedDate, NULL AS orderNote FROM t1 UNION SELECT *, NULL AS orderItemId FROM t2 I want to convert this to Linq query. The compiler didn't seem to be happy with it. Code) Next ' This code produces the following output: ' ' apple 9 ' orange 4 ' lemon 12 ' Poznámky. nullable reference types in C# 8). Enumerable. How to combine two c# objects using Linq. Possible solutions: 1) modify GetAttendanceListOf to return an empty list if no attendance (good idea in general, as null object pattern is very often a life saver, and for collection, an I'm trying to filter a DataTable using LINQ. MARKID The tables are generated correctly, but when I query the tables, EF generates a UNION on the User and HappyUser table. FirstOrDefault(), Is it nice way or could have even better? I tend to have the following somewhere in my code: public static IEnumerable<T> EmitFromEnum<T>(this T item) { yield return item; } While it's not as neat to call col. Key into temp from newRight in temp. The The proper way to handle things in this case isn't a Union. The question is similar to list union with duplicates in python. Whatever the return type of the Func passed to Select() will determine what type of object I have two LinqToSql queries that return result sets: var grResults = (from g in ctx. MyTable . Concat(y). Empty; this. 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