It’s unfortunately all too often recently that I’ve need to redirect assemblies, so I thought I’d write a quick post on the subject.
Occasionally you may have a situation where one library (let’s call it Lib1) you’re using in .NET relies on a specific version of a another, strong-named, library (let’s call it Lib2). Then you go and update the library Lib2 to a newer version and things break. Lib1 expects a specific version of Lib2 and we’re not supplying it.
Simple open/add your App.config file – we then add something like this
<runtime>
<assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
<dependentAssembly>
<assemblyIdentity name="Lib2" publicKeyToken="Lib2-PublicToken" culture="neutral" />
<bindingRedirect oldVersion="0.0.0.0-1.0.0.0" newVersion="2.0.0.0" />
</dependentAssembly>
</assemblyBinding>
</runtime>
Obviously you replace Lib2 with the assembly that your code is dependent upon, you’ll also need to supply the publicKeyToken. The oldVersion is a range of versions from 0.0.0.0 to 1.0.0.0 in this case, meaning anything that required this assembly version 0 to 1 should now use version 2 (2.0.0.0).
When adding further assembly redirects we of just supply further dependentAssembly elements.
To find the publicKeyToken we can use the Strong Name utility (sn.exe) which can be found here (for example)
"%ProgramFiles%\\Microsoft SDKs\Windows\v8.0A\bin\NETFX 4.0 Tools\sn.exe" -T <assemblyName>
We can also find such information via the likes of ILSpy, by clicking on the assembly and in the right hand pane we’ll have information such as
// Microsoft.VisualC, Version=8.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a
Further Reading