My app tries to deserialize data sent by client and it fails with the following error:
Exception thrown: \'System.Runtime.Serialization.Serializatio
Microsoft doesn't upload the source of every mscorlib.dll update, this is why you only get public PDBs without any source data. But there is a Visual Studio Addon from Redgate's Reflector where you can decompile 3rd party DLLs and step through them in the VS debugger.
DotPeek from Jetbrains also supports PDB generation and hosting of a Symbol server to allow debugging.
Maybe this helps you to debug your issue.