Queryable.Concat(Of TSource) Method (IQueryable(Of TSource), IEnumerable(Of TSource))


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Concatenates two sequences.

Namespace:   System.Linq
Assembly:  System.Core (in System.Core.dll)

Public Shared Function Concat(Of TSource) (
	source1 As IQueryable(Of TSource),
	source2 As IEnumerable(Of TSource)
) As IQueryable(Of TSource)


Type: System.Linq.IQueryable(Of TSource)

The first sequence to concatenate.

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.

Type Parameters


The type of the elements of the input sequences.

Exception Condition

source1 or source2 is null.

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
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

Universal Windows Platform
Available since 8
.NET Framework
Available since 3.5
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.1
Windows Phone
Available since 8.1
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