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ControlParameter::Evaluate Method

Updates and returns the value of the ControlParameter object.

Namespace:  System.Web.UI.WebControls
Assembly:  System.Web (in System.Web.dll)

protected:
virtual Object^ Evaluate(
	HttpContext^ context, 
	Control^ control
) override

Parameters

context
Type: System.Web::HttpContext

The current HttpContext of the request.

control
Type: System.Web.UI::Control

The Control that the parameter is bound to.

Return Value

Type: System::Object
An Object that represents the updated and current value of the parameter.

ExceptionCondition
ArgumentException

The ControlID property is not set.

- or -

The PropertyName property is not set and the Control identified by the ControlID property is not decorated with a ControlValuePropertyAttribute attribute.

InvalidOperationException

Control::FindControl does not return the specified control.

- or -

The control identified by the ControlID property does not support the property named by PropertyName.

The ControlParameter object attempts to bind to the Control object and property every time the Evaluate method is called. The Evaluate method returns the value of the control's property that is identified by the combination of the ControlID and PropertyName properties.

The ControlParameter class never uses the DefaultValue property, which is inherited from Parameter, when binding to a control's property value.

NoteNote:

In this implementation of the method, the context parameter is ignored. If the control parameter is nullptr, nullptr is returned.

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.

.NET Framework

Supported in: 3.5, 3.0, 2.0
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