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VerificationAttribute Class

Defines the metadata attribute of a Web content accessibility rule. This class cannot be inherited.

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

[AttributeUsageAttribute(AttributeTargets.Class|AttributeTargets.Property, AllowMultiple = true)]
[AspNetHostingPermissionAttribute(SecurityAction.LinkDemand, Level = AspNetHostingPermissionLevel.Minimal)]
public sealed class VerificationAttribute : Attribute

An instance of the VerificationAttribute class defines a Web content accessibility rule that can be verified. For more information on Web Content Accessibility Guidelines, see the World Wide Web Consortium (W3C) Web site.

The minimal amount of information required to define an instance of a VerificationAttribute includes:

  • A guideline that the verification rule represents. The value specified in the constructor sets the Guideline property.

  • A checkpoint of the guideline. The value specified in the constructor sets the Checkpoint property.

  • A checkpoint priority. The value specified in the constructor sets the Priority property.

  • A VerificationReportLevel enumeration value that represents the reporting level that should be rule belongs to. The value specified in the constructor sets the VerificationReportLevel property.

  • A message that is reported when the verification rule is true. The value specified in the constructor sets the Message property.

Optional properties of the verification rule that can be specified when creating an instance:

  • A VerificationRule enumeration value that represents how the verification rule should be interpreted. The value specified in the constructor sets the VerificationRule property.

  • A VerificationConditionalOperator enumeration value that represents the operator in the conditional expression used to test the verification rule. The value specified in the constructor sets the VerificationConditionalOperator property.

  • An accessibility reference guideline URL. The value specified in the constructor sets the GuidelineUrl property.

  • A conditional value representing the right side of a conditional expression. The value specified in the constructor sets the ConditionalValue property.

  • A conditional property representing the left side of a conditional expression. The value specified in the constructor sets the ConditionalProperty property.

The VerificationAttribute metadata can be defined class, property, and indexer declarations.

For more information about using attributes, see Extending Metadata Using Attributes.

The following code example demonstrates using the VerificationAttribute class. In the verification metadata definition, the guidelines used are "WCAG," the Web Content Accessibility Guideline, and "ADA," Americans with Disabilities Act Guidelines. For more information, see the World Wide Web Consortium (W3C) Web site.

The checkpoints used are "1.1" and "1194.22(a)" for WCAG and ADA, respectively, checkpoints for ensuring that a text equivalent exists for non-text elements. The VerificationAttribute is applied to the ImageText property that represents the text equivalent of another property called ImageProperty. If the ImageText property is not set, the accessibility verification will return the message "The image is missing a text equivalent."

		[Verification("ADA", "1194.22(a)", 
			VerificationReportLevel.Error, 1,
			"The image is missing a text equivalent.", 
			VerificationRule.NotEmptyString, "ImageUrl"),
		Verification("WCAG", "1.1", 
			VerificationReportLevel.Error, 1, 
			"The image is missing an text equivalent.", 
			VerificationRule.NotEmptyString, "ImageUrl")]
		public virtual String ImageText
		{
			get
			{
				object obj = ViewState["ImageText"];
				return ((obj == null) ? String.Empty : (string)obj);
			}
			set
			{
				ViewState["ImageText"] = value;
			}
		}
		public virtual String ImageUrl
		{
			get 
			{
				object obj = ViewState["ImageUrl"];
				return ((obj == null) ? String.Empty : (string)obj);
			}
			set 
			{ 
				ViewState["ImageUrl"] = value;
			}
		}

System.Object
  System.Attribute
    System.Web.UI.VerificationAttribute

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

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