Gets or sets a value that specifies the default extension string to use to filter the list of files that are displayed.
Assembly: PresentationFramework (in PresentationFramework.dll)
XMLNS for XAML: Not mapped to an xmlns.
The extension string must contain the leading period. For example, set the property to ".txt" to select all text files.
By default, the AddExtension property attempts to determine the extension to filter the displayed file list from the Filter property. If the extension cannot be determined from the Filter property, will be used instead.
Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.