Expression(TDelegate).Compile Method (System.Linq.Expressions)

Compile Method

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Microsoft Visual Studio 2008/.NET Framework 3.5

Other versions are also available for the following:

.NET Framework Class Library

Expression<(Of <(TDelegate>)>)..::.Compile Method

Compiles the lambda expression described by the expression tree into executable code.

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

Syntax

Visual Basic (Declaration)

Public Function Compile As TDelegate

Visual Basic (Usage)

Dim instance As Expression
Dim returnValue As TDelegate

returnValue = instance.Compile()

public TDelegate Compile()

Visual C++

public:
TDelegate Compile()

JScript

public function Compile() : TDelegate

Return Value

Type: TDelegate
A delegate of type TDelegate that represents the lambda expression described by the Expression<(Of <(TDelegate>)>).

Remarks

The Compile method produces a delegate of type TDelegate at runtime. When that delegate is executed, it has the behavior described by the semantics of the Expression<(Of <(TDelegate>)>).

The Compile method can be used to obtain the value of any expression tree. First, create a lambda expression that has the expression as its body by using the Lambda method. Then call Compile to obtain a delegate, and execute the delegate to obtain the value of the expression.

Examples

The following code example demonstrates how Compile is used to execute an expression tree.

Visual Basic

' Lambda expression as data in the form of an expression tree.
Dim expression As System.Linq.Expressions.Expression(Of Func(Of Integer, Boolean)) = Function(ByVal i) i < 5
' Compile the expression tree into executable code.
Dim deleg As Func(Of Integer, Boolean) = expression.Compile()
' Invoke the method and print the output.
MsgBox(String.Format("deleg(4) = {0}", deleg(4)))

' This code produces the following output:
'
' deleg(4) = True

// Lambda expression as data in the form of an expression tree.
System.Linq.Expressions.Expression<Func<int, bool>> expr = i => i < 5;
// Compile the expression tree into executable code.
Func<int, bool> deleg = expr.Compile();
// Invoke the method and print the output.
Console.WriteLine("deleg(4) = {0}", deleg(4));

/*  This code produces the following output:

    deleg(4) = True
*/

Platforms

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Version Information

.NET Framework

Supported in: 3.5

Reference

Expression<(Of <(TDelegate>)>) Class

Expression<(Of <(TDelegate>)>) Members

System.Linq.Expressions Namespace