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Change in path separator character in FullName property of ZipArchiveEntry objects

Scope

Edge

Version Introduced

4.6.1

Source Analyzer Status

Planned

Change Description

For apps that target the .NET Framework 4.6.1 and later versions, the path separator character has changed from a backslash ("\") to a forward slash ("/") in the xref:System.IO.Compression.ZipArchiveEntry.FullName property of xref:System.IO.Compression.ZipArchiveEntry objects created by overloads of the xref:System.IO.Compression.ZipFile.CreateFromDirectory%2A method. The change brings the .NET implementation into conformity with section 4.4.17.1 of the .ZIP File Format Specification and allows .ZIP archives to be decompressed on non-Windows systems.

Decompressing a zip file created by an app that targets a previous version of the .NET Framework on non-Windows operating systems such as the Macintosh fails to preserve the directory structure. For example, on the Macintosh, it creates a set of files whose filename concatenates the directory path, along with any backslash ("\") characters, and the filename. As a result, the directory structure of decompressed files is not preserved.

  • Quirked
  • Build-time break

Recommended Action

The impact of this change on .ZIP files that are decompressed on the Windows operating system by APIs in the .NET Framework xref:System.IO?displayProperty=nameWithType namespace should be minimal, since these APIs can seamlessly handle either a forward slash ("/") or a backslash ("\") as the path separator character.

If this change is undesirable, you can opt out of it by adding a configuration setting to the <runtime> section of your application configuration file. The following example shows both the <runtime> section and the Switch.System.IO.Compression.ZipFile.UseBackslash opt-out switch:

<runtime>
   <AppContextSwitchOverrides value="Switch.System.IO.Compression.ZipFile.UseBackslash=true" />
</runtime>

In addition, apps that target previous versions of the .NET Framework but are running on the .NET Framework 4.6.1 and later versions can opt in to this behavior by adding a configuration setting to the <runtime> section of the application configuration file. The following shows both the <runtime> section and the Switch.System.IO.Compression.ZipFile.UseBackslash opt-in switch.

<runtime>
   <AppContextSwitchOverrides value="Switch.System.IO.Compression.ZipFile.UseBackslash=false" />
</runtime>

Affected APIs

  • M:System.IO.Compression.ZipFile.CreateFromDirectory(System.String,System.String)
  • M:System.IO.Compression.ZipFile.CreateFromDirectory(System.String,System.String,System.IO.Compression.CompressionLevel,System.Boolean)
  • M:System.IO.Compression.ZipFile.CreateFromDirectory(System.String,System.String,System.IO.Compression.CompressionLevel,System.Boolean,System.Text.Encoding)

Category

Core