Gets the expression prefix that identifies expression strings that are supported by the expression editor implementation.
Assembly: System.Design (in System.Design.dll)
The expression prefix identifies the custom expression type and associates an expression with the expression builder and expression editor. When custom expressions are parsed in a page, the expression prefix is used to create instances of the associated ExpressionBuilder and ExpressionEditor classes. To associate an expression prefix with an expression builder and expression editor, apply the ExpressionEditorAttribute and ExpressionPrefixAttribute attributes to the custom ExpressionBuilder class and configure the expression prefix for an expression builder in the expressionBuilders element in the Web configuration file.