Queryable.Concat<TSource> Method

Definition

Namespace:

System.Linq

Assembly:

System.Linq.Queryable.dll

Source:

Queryable.cs

Concatenates two sequences.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static System::Linq::IQueryable<TSource> ^ Concat(System::Linq::IQueryable<TSource> ^ source1, System::Collections::Generic::IEnumerable<TSource> ^ source2);

public static System.Linq.IQueryable<TSource> Concat<TSource> (this System.Linq.IQueryable<TSource> source1, System.Collections.Generic.IEnumerable<TSource> source2);

static member Concat : System.Linq.IQueryable<'Source> * seq<'Source> -> System.Linq.IQueryable<'Source>

<Extension()>
Public 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

IQueryable<TSource>

The first sequence to concatenate.

source2

IEnumerable<TSource>

The sequence to concatenate to the first sequence.

Returns

IQueryable<TSource>

An IQueryable<T> that contains the concatenated elements of the two input sequences.

Exceptions

ArgumentNullException

source1 or source2 is null.

Examples

The following code example demonstrates how to use Concat<TSource>(IQueryable<TSource>, IEnumerable<TSource>) to concatenate two sequences.

class Pet
{
    public string Name { get; set; }
    public int Age { get; set; }
}

// This method creates and returns an array of Pet objects.
static Pet[] GetCats()
{
    Pet[] cats = { new Pet { Name="Barley", Age=8 },
                   new Pet { Name="Boots", Age=4 },
                   new Pet { Name="Whiskers", Age=1 } };
    return cats;
}

// This method creates and returns an array of Pet objects.
static Pet[] GetDogs()
{
    Pet[] dogs = { new Pet { Name="Bounder", Age=3 },
                   new Pet { Name="Snoopy", Age=14 },
                   new Pet { Name="Fido", Age=9 } };
    return dogs;
}

public static void ConcatEx1()
{
    Pet[] cats = GetCats();
    Pet[] dogs = GetDogs();

    // Concatenate a collection of cat names to a
    // collection of dog names by using Concat().
    IEnumerable<string> query =
        cats.AsQueryable()
        .Select(cat => cat.Name)
        .Concat(dogs.Select(dog => dog.Name));

    foreach (string name in query)
        Console.WriteLine(name);
}

// This code produces the following output:
//
// Barley
// Boots
// Whiskers
// Bounder
// Snoopy
// Fido

' 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
        MsgBox(name)
    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

Remarks

The Concat<TSource>(IQueryable<TSource>, IEnumerable<TSource>) method generates a MethodCallExpression that represents calling Concat<TSource>(IQueryable<TSource>, IEnumerable<TSource>) itself as a constructed generic method. It then passes the MethodCallExpression to the CreateQuery<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<TSource>(IQueryable<TSource>, IEnumerable<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.