ExpressionPrefixAttribute Class
Specifies the prefix attribute to use for the expression builder. This class cannot be inherited.
Assembly: System.Web (in System.Web.dll)
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.
<configuration>
<system.web>
<compilation>
<expressionBuilders>
<add expressionPrefix="MyCustomExpression"
type="MyCustomExpressionBuilder"/>
</expressionBuilders>
</compilation>
</system.web>
</configuration>
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.
- AspNetHostingPermission
for operating in a hosted environment. Demand value: LinkDemand; Permission value: Minimal.
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.