Queryable.Concat(Of TSource) Method
[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]
Concatenates two sequences.
Assembly: System.Core (in System.Core.dll)
'Declaration <ExtensionAttribute> _ Public Shared Function Concat(Of TSource) ( _ source1 As IQueryable(Of TSource), _ source2 As IEnumerable(Of TSource) _ ) As IQueryable(Of TSource)
Type Parameters
- TSource
The type of the elements of the input sequences.
Parameters
- source1
- Type: System.Linq.IQueryable(Of TSource)
The first sequence to concatenate.
- source2
- Type: System.Collections.Generic.IEnumerable(Of TSource)
The sequence to concatenate to the first sequence.
Return Value
Type: System.Linq.IQueryable(Of TSource)An IQueryable(Of T) that contains the concatenated elements of the two input sequences.
Usage Note
In Visual Basic and C#, you can call this method as an instance method on any object of type IQueryable(Of TSource). When you use instance method syntax to call this method, omit the first parameter.| Exception | Condition |
|---|---|
| ArgumentNullException | source1 or source2 is Nothing. |
The Concat(Of TSource)(IQueryable(Of TSource), IEnumerable(Of TSource)) method generates a MethodCallExpression that represents calling Concat(Of TSource)(IQueryable(Of TSource), IEnumerable(Of TSource)) itself as a constructed generic method. It then passes the MethodCallExpression to the CreateQuery(Of TElement)(Expression) method of the IQueryProvider represented by the Provider property of the source1 parameter.
The query behavior that occurs as a result of executing an expression tree that represents calling Concat(Of TSource)(IQueryable(Of TSource), IEnumerable(Of TSource)) depends on the implementation of the type of the source1 parameter. The expected behavior is that the elements in source2 are concatenated to those of source1 to create a new sequence.
The following code example demonstrates how to use Concat(Of TSource)(IQueryable(Of TSource), IEnumerable(Of TSource)) to concatenate two sequences.
' This method creates and returns an array of Pet objects. Shared Function GetCats() As Pet() Dim cats() As Pet = _ {New Pet With {.Name = "Barley", .Age = 8}, _ New Pet With {.Name = "Boots", .Age = 4}, _ New Pet With {.Name = "Whiskers", .Age = 1}} Return cats End Function ' This method creates and returns an array of Pet objects. Shared Function GetDogs() As Pet() Dim dogs() As Pet = _ {New Pet With {.Name = "Bounder", .Age = 3}, _ New Pet With {.Name = "Snoopy", .Age = 14}, _ New Pet With {.Name = "Fido", .Age = 9}} Return dogs End Function Shared Sub ConcatEx1() Dim cats() As Pet = GetCats() Dim dogs() As Pet = GetDogs() ' Concatenate a collection of cat names to a ' collection of dog names by using Concat(). Dim query As IEnumerable(Of String) = _ cats.AsQueryable() _ .Select(Function(cat) cat.Name) _ .Concat(dogs.Select(Function(dog) dog.Name)) For Each name As String In query outputBlock.Text &= name & vbCrLf Next End Sub Structure Pet Dim Name As String Dim Age As Integer End Structure ' This code produces the following output: ' ' Barley ' Boots ' Whiskers ' Bounder ' Snoopy ' Fido