If you want to create a managed plugin for unity3d engine, you need provide a mdb file for debugging. With the update of VS, Unity's built-in pdb2mdb.exe may no longer work properly. Some enthusiastic netizens on the Internet provide a new pdb2mdb.exe, but I also encounter problems when using it, such as when the project is very large , Dll, pdb file size is 100M+. the common error like this: Fatal error: Microsoft.Cci.Pdb.PdbDebugException: Invalid signature. (sig=1919117645) in Microsoft.Cci.Pdb.PdbFile.LoadFuncsFromDbiModule(BitAccess bits, DbiModuleInfo info, IntHashTable names, ArrayList funcList, Boolean readStrings, MsfDirectory dir, Dictionary`2 nameIndex, PdbReader reader) in Microsoft.Cci.Pdb.PdbFile.LoadFunctions(Stream read, BitAccess bits, Boolean readAllStrings) in Pdb2Mdb.Driver.Convert(AssemblyDefinition assembly, Stream pdb, MonoSymbolWriter mdb)
So I found the source code of pdb2mdb from the source code of mono, and tried to upgrade all its dependencies to the latest, fix the compile error by change some codes which is not compatible with the new codes, and recompile them. so I got a new version of pdb2mdb, this version of pdb2mdb can solve my problem, There is no guarantee that it will solve your problem, you can try it. If you want to compile this project by yourself, just open the sln file with vs2019 and compile it directly. prebuild release can be found in pdb2mdb/bin/Release
usage: makesure your dll has a pdb file, and project settings full, and then: pdb2mdb xxx.dll eg : pdb2mdb.exe D:\test.dll don't use D:\test.pdb
中文(Chinese): 简单来说，以前网上下载的pdb2mdb.exe在转一些特别的dll和pdb时，会报上面的异常。为了解决这个问题，我自己通过搜集相关三方代码和依赖库，重新编译了一个新版本的pdb2mdb。由于很多新三方代码互相之间不兼容，我还对一些代码做出了修改和调整，确保转出来的mdb可以帮助我们的dll在Unity引擎下面调试正常。如果你也遇到了上面说的异常，不妨一试我这个。如果并没有遇到，那么建议你继续用以前的。
pdb2mdb.exe
https://gist.github.com/jbevain/ba23149da8369e4a966f
microsoft.cci
https://github.com/microsoft/cci
DiaSymReader
https://www.nuget.org/packages/Microsoft.DiaSymReader/
DiaSymReader.Converter
https://github.com/dotnet/symreader-converter
DiaSymReader.Converter Prebuild Binaries
https://dev.azure.com/dnceng/public/_packaging?_a=feed&feed=dotnet-tools
Mono.Cecil
https://github.com/jbevain/cecil
Mono
https://github.com/mono/mono
System.Collections.Immutable
https://www.nuget.org/packages/System.Collections.Immutable/6.0.0-preview.6.21352.12