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Expression.Call Method (Expression, MethodInfo)

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Creates a MethodCallExpression that represents a call to an instance method that takes no arguments.

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

Syntax

'Declaration
Public Shared Function Call ( _
    instance As Expression, _
    method As MethodInfo _
) As MethodCallExpression

public static MethodCallExpression Call(
    Expression instance,
    MethodInfo method
)

Parameters

  • instance
    Type: System.Linq.Expressions.Expression
    An Expression that specifies the instance for an instance method call (pass nulla null reference (Nothing in Visual Basic) for a static (Shared in Visual Basic) method).

Return Value

Type: System.Linq.Expressions.MethodCallExpression
A MethodCallExpression that has the NodeType property equal to Call and the Object and Method properties set to the specified values.

Exceptions

Exception Condition
ArgumentNullException

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

-or-

instance is nulla null reference (Nothing in Visual Basic) and method represents an instance method.
ArgumentException

instance.Type is not assignable to the declaring type of the method represented by method.

Remarks

To represent a call to a static (Shared in Visual Basic) method, pass in nulla null reference (Nothing in Visual Basic) for the instance parameter when you call this method.

If method represents an instance method, the Type property of instance must be assignable to the declaring type of the method represented by method.

The Arguments property of the resulting MethodCallExpression is empty. The Type property is equal to the return type of the method represented by method.

Examples

The following code example shows how to create an expression that calls a method without arguments.

        ' Add the following directive to your file:
        ' Imports System.Linq.Expressions   

        ' This expression represents a call to an instance method without arguments.
        Dim callExpr As Expression = Expression.Call(
            Expression.Constant("sample string"), GetType(String).GetMethod("ToUpper", New Type() {}))

        ' Print the expression.
        outputBlock.Text &= callExpr.ToString() & vbCrLf

        ' The following statement first creates an expression tree,
        ' then compiles it, and then executes it.  
        outputBlock.Text &= Expression.Lambda(Of Func(Of String))(callExpr).Compile()() & vbCrLf

        ' This code example produces the following output:
        '
        ' "sample string".ToUpper
        ' SAMPLE STRING


       // Add the following directive to your file:
       // using System.Linq.Expressions;  

       // This expression represents a call to an instance method without arguments.
       Expression callExpr = Expression.Call(
           Expression.Constant("sample string"), typeof(String).GetMethod("ToUpper", new Type[] { }));

       // Print out the expression.
       outputBlock.Text += callExpr.ToString() + "\n";

       // The following statement first creates an expression tree,
       // then compiles it, and then executes it.  
       outputBlock.Text += Expression.Lambda<Func<String>>(callExpr).Compile()() + "\n";

       // This code example produces the following output:
       //
       // "sample string".ToUpper
       // SAMPLE STRING

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Windows Phone OS 7.0

Platforms

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