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IdnMapping.UseStd3AsciiRules Property

Gets or sets a value indicating whether standard or nonstandard naming conventions are used in operations performed by members of the current IdnMapping object.

Namespace:  System.Globalization
Assembly:  mscorlib (in mscorlib.dll)

public bool UseStd3AsciiRules { get; set; }

Property Value

Type: System.Boolean
true if nonstandard naming conventions are used in operations; otherwise, false.

Domain names that follow standard naming rules consist of characters in the US-ASCII character range. The characters are the letters A through Z, the digits 0 through 9, the hyphen (-) character, and the period (.) character. The case of the domain name is not significant.

For more information, see the RFC 1122 standard, "Requirements for Internet Hosts – Communication Layers," at Request for Comments (RFC).


The IdnMapping class prohibits the use of the nondisplayable characters U+0000 through U+001F and U+007F in domain name labels regardless of the setting of the UseStd3AsciiRules property. This prohibition reduces the risk of security attacks such as name spoofing.

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.