ExpressionPrefixAttribute Class

ExpressionPrefixAttribute Class


Specifies the prefix attribute to use for the expression builder. This class cannot be inherited.

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


[AttributeUsageAttribute(AttributeTargets.Class, AllowMultiple = false)]
public sealed class ExpressionPrefixAttribute : Attribute


Initializes a new instance of the ExpressionPrefixAttribute class.


Gets the prefix value for the current ExpressionBuilder object.


When implemented in a derived class, gets a unique identifier for this Attribute.(Inherited from Attribute.)


This API supports the product infrastructure and is not intended to be used directly from your code. Returns a value that indicates whether this instance is equal to a specified object.(Inherited from Attribute.)


Returns the hash code for this instance.(Inherited from Attribute.)


Gets the Type of the current instance.(Inherited from Object.)


When overridden in a derived class, indicates whether the value of this instance is the default value for the derived class.(Inherited from Attribute.)


When overridden in a derived class, returns a value that indicates whether this instance equals a specified object.(Inherited from Attribute.)


Returns a string that represents the current object.(Inherited from Object.)

System_CAPS_pubinterfaceSystem_CAPS_privmethod_Attribute.GetIDsOfNames(Guid, IntPtr, UInt32, UInt32, IntPtr)

Maps a set of names to a corresponding set of dispatch identifiers.(Inherited from Attribute.)

System_CAPS_pubinterfaceSystem_CAPS_privmethod_Attribute.GetTypeInfo(UInt32, UInt32, IntPtr)

Retrieves the type information for an object, which can be used to get the type information for an interface.(Inherited from Attribute.)


Retrieves the number of type information interfaces that an object provides (either 0 or 1).(Inherited from Attribute.)

System_CAPS_pubinterfaceSystem_CAPS_privmethod_Attribute.Invoke(UInt32, Guid, UInt32, Int16, IntPtr, IntPtr, IntPtr, IntPtr)

Provides access to properties and methods exposed by an object.(Inherited from Attribute.)

The ExpressionPrefixAttribute class is used at design time with expressions that are not defined in the configuration file. Use the ExpressionPrefix property to get the name of the prefix that is associated with the ExpressionPrefixAttribute object. An expression builder looks for any statements with the following form:

<%$ [expressionPrefix]:[expressionValue] %>

Then the expression builder, based on the prefix of the expression, generates code for the property assignment. The expressionPrefix parameter refers to a configured expression builder, which is defined in the configuration file or through an ExpressionPrefixAttribute object.

The following code examples demonstrate how to use the ExpressionPrefixAttribute class. The attribute is applied to a custom expression builder that implements the ExpressionBuilder abstract class. This implementation of ExpressionBuilder returns an evaluated statement that is passed to the expression. To run this example, you must first register the custom expression builder in the Web.config file. The first code example demonstrates how to register the custom expression builder in the Web.config file.

              <add expressionPrefix="MyCustomExpression"

The second code example demonstrates how to reference the expression in an .aspx file.

<asp:Label ID="Label1" runat="server" 
Text="<%$ MyCustomExpression:Hello, world! %>" />

The third code example demonstrates how to develop a customized expression builder by deriving from ExpressionBuilder. To run this code example, you must place the class in the App_Code folder.

.NET Framework
Available since 2.0

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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