AppSettingsExpressionEditor Class

Reference

Definition

Namespace:: System.Web.UI.Design

Assembly:: System.Design.dll

Important

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Provides properties and methods for evaluating and editing an application setting expression in a configuration file at design time.

public ref class AppSettingsExpressionEditor : System::Web::UI::Design::ExpressionEditor

public class AppSettingsExpressionEditor : System.Web.UI.Design.ExpressionEditor

type AppSettingsExpressionEditor = class
    inherit ExpressionEditor

Public Class AppSettingsExpressionEditor
Inherits ExpressionEditor

Inheritance: Object

ExpressionEditor
AppSettingsExpressionEditor

Examples

The following code example demonstrates how to bind the NavigateUrl property of a HyperLink control to an application setting expression using the AppSettingsExpressionEditor object.

In a Web Forms project, add MyHyperLinkSetting to the <appSettings> section of the web.config file.

<FileName>web.config</FileName>
<RelevantItems>
    <Reference>System.Web.UI.Design.AppSettingExpressionEditor</Reference>
</RelevantItems>

On a Web Forms page, add a HyperLink control.
For the Hyperlink control, in Properties, click Expressions, and then click the ellipsis button (...).

The <Hyperlinkname>Expression dialog box appears.
Under Bindable properties, click NavigateUrl, in the Expression type list, click AppSettings, and then under Expression properties, in the AppSetting box, type MyHyperLinkSetting.

The visual designer uses the AppSettingsExpressionEditor to assign the expression for the NavigateUrl property.

The following aspx source shows an example of a property value set using an application setting expression.

<!-- Define a hyperlink that maps the NavigateUrl property to the
     MyHyperLinkSetting value in the Web.Config appSettings section. -->
<asp:HyperLink runat="server" ID="HyperLink1" 
     NavigateUrl="<%$ AppSettings:MyHyperLinkSetting %>">
     HyperLink using an AppSetting expression
</asp:HyperLink>

<!-- Define a hyperlink that maps the NavigateUrl property to the
     MyHyperLinkSetting value in the Web.Config appSettings section. -->
<asp:HyperLink runat="server" ID="HyperLink1" 
     NavigateUrl="<%$ AppSettings:MyHyperLinkSetting %>">
     HyperLink using an AppSetting expression
</asp:HyperLink>

<FileName>ControlsUsingExpressions.aspx</FileName>
<RelevantItems>
    <Reference>System.Web.UI.Design.AppSettingExpressionEditor</Reference>
</RelevantItems>

Remarks

The AppSettingsExpressionEditor class is derived from the ExpressionEditor class and provides an implementation for evaluating and associating an application setting reference with a control property at design time. For example, you can bind the value of a control property to the application setting expression AppSettings:mySettingKeyName, which indicates that the control property value is set using the mySettingKeyName value in the appSettings section of the Web configuration file.

A visual designer host, such as Visual Studio 2005, uses the AppSettingsExpressionEditor class to select an application setting from the appSettings configuration section, and then evaluates the selected expression for design-time rendering.

When you browse to the Expressions property for a control in the design-time properties grid, the visual designer displays a dialog box to set expressions that provide the run-time value for a control property. You can select the expression type based on a list of expression prefixes. When you select the AppSettings expression prefix from the list, the visual designer host uses the associated ExpressionEditorSheet object to provide design-time editing functionality of appSettings expressions and uses AppSettingsExpressionEditor methods to evaluate and convert the expression string based on the syntax for an application setting expression. The visual designer host uses the evaluated expression result to assign control property values that are rendered on the design surface.

The ExpressionPrefix property for an AppSettingsExpressionEditor object returns the string AppSettings. The AppSettingsExpressionBuilder class is associated with the expression prefix AppSettings and the AppSettingsExpressionEditor implementation.

The EvaluateExpression method evaluates an input application setting expression string. The GetExpressionEditorSheet method returns the ExpressionEditorSheet implementation that is used to enter and edit application setting expressions.

Constructors

AppSettingsExpressionEditor()

Initializes a new instance of the AppSettingsExpressionEditor class.

Properties

ExpressionPrefix

Gets the expression prefix that identifies expression strings that are supported by the expression editor implementation.

(Inherited from ExpressionEditor)

Methods

Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object)
EvaluateExpression(String, Object, Type, IServiceProvider)	Evaluates an application setting expression string and provides the design-time value for a control property.
GetExpressionEditorSheet(String, IServiceProvider)	Returns an expression editor sheet for an application setting expression.
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetType()	Gets the Type of the current instance. (Inherited from Object)
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
ToString()	Returns a string that represents the current object. (Inherited from Object)

Applies to

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