AmbientValueAttribute Class
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AmbientValueAttribute Class

Specifies the value to pass to a property to cause the property to get its value from another source. This is known as ambience. This class cannot be inherited.

Namespace:  System.ComponentModel
Assembly:  System (in System.dll)

<AttributeUsageAttribute(AttributeTargets.All)> _
Public NotInheritable Class AmbientValueAttribute _
	Inherits Attribute
Dim instance As AmbientValueAttribute

If a property on a control has ambient behavior, this attribute must be present. Ambient properties query their parent for their value, for example, a Control.Font property or a Control.BackColor property.

Typically, a visual designer uses the AmbientValueAttribute attribute to decide which value to persist for a property. This is usually a value that causes the property to get its value from another source. An example of an ambient value is Color.Empty as the ambient value for the BackColor property. If you have a control on a form and the BackColor property of the control is set to a different color than the BackColor property of the form, you can reset the BackColor property of the control to that of the form by setting the BackColor of the control to Color.Empty.

The following code example demonstrates using AmbientValueAttribute to enforce ambient behavior for a property called AlertForeColor. For a full code listing, see How to: Apply Attributes in Windows Forms Controls.

<AmbientValue(GetType(Color), "Empty"), _
Category("Appearance"), _
DefaultValue(GetType(Color), "White"), _
Description("The color used for painting alert text.")> _
Public Property AlertForeColor() As Color
        If Me.alertForeColorValue = Color.Empty AndAlso (Me.Parent IsNot Nothing) Then 
            Return Parent.ForeColor
        End If 

        Return Me.alertForeColorValue
    End Get 

    Set(ByVal value As Color)
        Me.alertForeColorValue = value
    End Set 
End Property 

' This method is used by designers to enable resetting the 
' property to its default value. 
Public Sub ResetAlertForeColor()
    Me.AlertForeColor = AttributesDemoControl.defaultAlertForeColorValue
End Sub 

' This method indicates to designers whether the property 
' value is different from the ambient value, in which case 
' the designer should persist the value. 
Private Function ShouldSerializeAlertForeColor() As Boolean 
    Return Me.alertForeColorValue <> AttributesDemoControl.ambientColorValue
End Function


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

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, 1.1, 1.0

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