Resolution of Assembly Binding Redirections

PostSharp executes your project assemblies at build time. This is why PostSharp must follow assembly binding redirections at build time. Although the default assembly redirection mechanism works fine in most cases, there may be situations where you will need to override it.

Note

To learn why PostSharp executes your project assemblies at build time, see Understanding Aspect Lifetime and Scope.

Default assembly binding redirections

To follow the same assembly binding redirections as your application does at run time, PostSharp analyzes your projects and configuration files (typically app.config or web.config) and generates assembly binding redirection configuration. PostSharp stores the assembly binding redirection in a file named postsharp.app.config in the PostSharp subdirectory of the intermediate output directory (for instance obj\Debug\PostSharp). You can review the postsharp.app.config file to see what configuration PostSharp uses to resolve assemblies. For an empty ASP.NET MVC 5 application, the postsharp.app.config file may look like this:

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<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <dependentAssembly>
        <assemblyIdentity name="Microsoft.Owin.Security" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="0.0.0.0-3.0.1.0" newVersion="3.0.1.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="Microsoft.Owin.Security.OAuth" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="0.0.0.0-3.0.1.0" newVersion="3.0.1.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="Microsoft.Owin.Security.Cookies" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="0.0.0.0-3.0.1.0" newVersion="3.0.1.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="Microsoft.Owin" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="0.0.0.0-3.0.1.0" newVersion="3.0.1.0" />
      </dependentAssembly>
    </assemblyBinding>
  </runtime>
</configuration>

Note

PostSharp relies on the GenerateBindingRedirects MSBuild task.

Overriding default assembly redirections

If the default mechanism does not work, you can disable it by setting the MSBuild property PostSharpDisableDefaultBindingRedirects to True in your project file:

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<PropertyGroup>
  <PostSharpDisableDefaultBindingRedirects>True</PostSharpDisableDefaultBindingRedirects>
</PropertyGroup>

With this configuration, PostSharp does not analyze assembly binding redirections.

Warning

Do not set PostSharpDisableDefaultBindingRedirects to True unless it is necessary. It may produce results that are difficult to predict.

Note

The default algorithm applies only to projects that target .NET Framework. It is disabled for projects that target .NET Core, .NET 5 and later, or .NET Standard.

If you disable default binding redirections, you may want to specify a file with your own assembly binding redirection configuration:

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<PropertyGroup>
  <PostSharpDisableDefaultBindingRedirects>True</PostSharpDisableDefaultBindingRedirects>
  <PostSharpHostConfigurationFile>web.config</PostSharpHostConfigurationFile>
</PropertyGroup>

With this configuration, PostSharp uses explicit assembly binding redirection configuration from the web.config file.