Export (0) Print
Expand All

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)

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


Type: System.Web.UI.BoundPropertyEntry

The object that represents information about the property bound to by the expression.

Type: System.Object

The object containing parsed data as returned by ParseExpression.

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.

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.

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

    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));

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0
© 2015 Microsoft