• Article

Queryable.Concat<TSource> Method

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Concatenates two sequences.

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

Syntax

'Declaration
<ExtensionAttribute> _
Public Shared Function Concat(Of TSource) ( _
    source1 As IQueryable(Of TSource), _
    source2 As IEnumerable(Of TSource) _
) As IQueryable(Of TSource)

public static IQueryable<TSource> Concat<TSource>(
    this IQueryable<TSource> source1,
    IEnumerable<TSource> source2
)

Type Parameters

  • TSource
    The type of the elements of the input sequences.

Parameters

Return Value

Type: System.Linq.IQueryable<TSource>
An IQueryable<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<TSource>. When you use instance method syntax to call this method, omit the first parameter.

Exceptions

Exception Condition
ArgumentNullException

source1 or source2 is nulla null reference (Nothing in Visual Basic).

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.

Examples

The following code example demonstrates how to use Concat<TSource>(IQueryable<TSource>, IEnumerable<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


         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)
               outputBlock.Text += name + "\n";
         }

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

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.