ExpressionBuilder.GetCodeExpression Method (System.Web.Compilation)

GetCodeExpression Method

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This page is specific to

Microsoft Visual Studio 2008/.NET Framework 3.5

Other versions are also available for the following:

.NET Framework Class Library

ExpressionBuilder..::.GetCodeExpression Method

When overridden in a derived class, returns code that is used during page execution to obtain the evaluated expression.

Namespace: System.Web.Compilation
Assembly: System.Web (in System.Web.dll)

Syntax

Visual Basic (Declaration)

Public MustOverride Function GetCodeExpression ( _
    entry As BoundPropertyEntry, _
    parsedData As Object, _
    context As ExpressionBuilderContext _
) As CodeExpression

Visual Basic (Usage)

Dim instance As ExpressionBuilder
Dim entry As BoundPropertyEntry
Dim parsedData As Object
Dim context As ExpressionBuilderContext
Dim returnValue As CodeExpression

returnValue = instance.GetCodeExpression(entry, _
    parsedData, context)

public abstract CodeExpression GetCodeExpression(
    BoundPropertyEntry entry,
    Object parsedData,
    ExpressionBuilderContext context
)

Visual C++

public:
virtual CodeExpression^ GetCodeExpression(
    BoundPropertyEntry^ entry, 
    Object^ parsedData, 
    ExpressionBuilderContext^ context
) abstract

JScript

public abstract function GetCodeExpression(
    entry : BoundPropertyEntry, 
    parsedData : Object, 
    context : ExpressionBuilderContext
) : CodeExpression

Parameters

entry: Type: System.Web.UI..::.BoundPropertyEntry
The object that represents information about the property bound to by the expression.

parsedData: Type: System..::.Object
The object containing parsed data as returned by ParseExpression.

context: Type: System.Web.Compilation..::.ExpressionBuilderContext
Contextual information for the evaluation of the expression.

Return Value

Type: System.CodeDom..::.CodeExpression
A CodeExpression that is used for property assignment.

Remarks

Classes that inherit from the ExpressionBuilder class must implement the GetCodeExpression abstract method.

Notes to Inheritors:

If you implement a custom expression builder, you must perform the proper type casting for the control property and return the cast operation in the CodeExpression object.

Examples

The following code example demonstrates how to return a CodeExpression object by overriding the GetCodeExpression method.

Visual Basic

Public Overrides Function GetCodeExpression(ByVal entry _
   As BoundPropertyEntry, ByVal parsedData As Object, ByVal context _
   As ExpressionBuilderContext) As CodeExpression
    Dim type1 As Type = entry.DeclaringType
    Dim descriptor1 As PropertyDescriptor = _
       TypeDescriptor.GetProperties(type1)(entry.PropertyInfo.Name)
    Dim expressionArray1(2) As CodeExpression
    expressionArray1(0) = New CodePrimitiveExpression(entry.Expression.Trim())
    expressionArray1(1) = New CodeTypeOfExpression(type1)
    expressionArray1(2) = New CodePrimitiveExpression(entry.Name)
    Return New CodeCastExpression(descriptor1.PropertyType, _
       New CodeMethodInvokeExpression(New CodeTypeReferenceExpression _
       (MyBase.GetType()), "GetEvalData", expressionArray1))
End Function

    public override CodeExpression GetCodeExpression(BoundPropertyEntry entry, 
    object parsedData, ExpressionBuilderContext context)
    {
        Type type1 = entry.DeclaringType;
        PropertyDescriptor descriptor1 = TypeDescriptor.GetProperties(type1)[entry.PropertyInfo.Name];
        CodeExpression[] expressionArray1 = new CodeExpression[3];
        expressionArray1[0] = new CodePrimitiveExpression(entry.Expression.Trim());
        expressionArray1[1] = new CodeTypeOfExpression(type1);
        expressionArray1[2] = new CodePrimitiveExpression(entry.Name);
        return new CodeCastExpression(descriptor1.PropertyType, new CodeMethodInvokeExpression(new 
       CodeTypeReferenceExpression(base.GetType()), "GetEvalData", expressionArray1));
    }

Platforms

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

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, 3.0, 2.0

Reference

ExpressionBuilder Class

ExpressionBuilder Members

System.Web.Compilation Namespace