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Mitigation: Path Colon Checks

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Starting with apps that target the .NET Framework 4.6.2, a number of changes were made to support previously unsupported paths (both in terms of length and format). In particular, checks for the proper drive separator syntax (the colon) were made more correct.

Impact

These changes block some URI paths the Path.GetDirectoryName and Path.GetPathRoot methods previously supported.

Mitigation

To work around the problem of a previously acceptable path that is no longer supported by the Path.GetDirectoryName and Path.GetPathRoot methods, you can do the following:

  • Manually remove the scheme from a URL. For example, remove file:// from a URL.

  • Pass the URI to a Uri constructor, and retrieve the value of the Uri.LocalPath property.

  • Opt out of the new path normalization by setting the Switch.System.IO.UseLegacyPathHandlingAppContext switch to true.

    <runtime>  
    <AppContextSwitchOverrides value="Switch.System.IO.UseLegacyPathHandling=true" />
</runtime>

See also