• Articolo

Queryable.Take<TSource> Method

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Returns a specified number of contiguous elements from the start of a sequence.

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

Syntax

'Declaration
<ExtensionAttribute> _
Public Shared Function Take(Of TSource) ( _
    source As IQueryable(Of TSource), _
    count As Integer _
) As IQueryable(Of TSource)

public static IQueryable<TSource> Take<TSource>(
    this IQueryable<TSource> source,
    int count
)

Type Parameters

  • TSource
    The type of the elements of source.

Parameters

  • count
    Type: System.Int32
    The number of elements to return.

Return Value

Type: System.Linq.IQueryable<TSource>
An IQueryable<T> that contains the specified number of elements from the start of source.

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

source is nulla null reference (Nothing in Visual Basic).

Remarks

The Take<TSource>(IQueryable<TSource>, Int32) method generates a MethodCallExpression that represents calling Take<TSource>(IQueryable<TSource>, Int32) itself as a constructed generic method. It then passes the MethodCallExpression to the CreateQuery(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

The query behavior that occurs as a result of executing an expression tree that represents calling Take<TSource>(IQueryable<TSource>, Int32) depends on the implementation of the type of the source parameter. The expected behavior is that it takes the first count elements from the start of source.

Examples

The following code example demonstrates how to use Take<TSource>(IQueryable<TSource>, Int32) to return elements from the start of a sequence.

      Dim grades() As Integer = {59, 82, 70, 56, 92, 98, 85}

      ' Sort the grades in descending order and take the first three.
      Dim topThreeGrades = _
          grades.AsQueryable().OrderByDescending(Function(grade) grade).Take(3)

      Dim output As New System.Text.StringBuilder
      output.AppendLine("The top three grades are:")
      For Each grade As Integer In topThreeGrades
         output.AppendLine(grade)
      Next

      ' Display the output.
      outputBlock.Text &= output.ToString() & vbCrLf

      ' This code produces the following output:

      ' The top three grades are:
      ' 98
      ' 92
      ' 85


         int[] grades = { 59, 82, 70, 56, 92, 98, 85 };

         // Sort the grades in descending order and take the first three.
         IEnumerable<int> topThreeGrades =
             grades.AsQueryable().OrderByDescending(grade => grade).Take(3);

         outputBlock.Text += "The top three grades are:" + "\n";
         foreach (int grade in topThreeGrades)
            outputBlock.Text += grade + "\n";

         /*
             This code produces the following output:

             The top three grades are:
             98
             92
             85
         */

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.