If you are getting runtime errors regarding "strong name" or "public key token" mismatches, be aware that later versions of log4net (like 1.2.11+) changed the assembly versioning scheme (they started using 1.2.11.0 , then 1.2.12.0 , etc.).

If you are replacing a DLL in an existing application, ensure the PublicKeyToken matches. For Apache log4net (newer signed versions), the token is usually 669e0ddf0bb1aa2a .

: Some specialized NuGet packages, like log4net.1.2.10.Raygun, specifically bundle this version for compatibility reasons. 2. Why Version 1.2.10.0 is Unique

: If a library you use (like Crystal Reports) was compiled against the "old" key (1.2.10), you cannot simply swap it for a newer version without an assembly redirect—and even then, redirects only work if the public key matches, which it doesn't between these two specific versions. 3. Common Issues and Fixes

: Version 1.2.10 used an "old" strong name key. Starting with 1.2.11, Apache switched to a "new" key.

Once installed, you need to configure your App.config or Web.config . Here is a minimal example for version 1.2.10: