What could be causing a System.TypeLoadException?

Question

I'm developing, with VS2008 using C#, an application for Honeywell Dolphin 6100, a mobile computer with a barcode scanner that uses Windows CE 5.0 like OS.

I want to add a functionality that can send files from the local device to the distant server. I found the library "Tamir.SharpSSH" which can guarantee this. I tested the code on a console application and on normal windows forms application and it works perfectly. But when I tried to use the same code on the winCE device, I get a TypeLoadException and I have the error message:

Could not load type 'Tamir.SharpSsh.SshTransferProtocolBase' from assembly 'Tamir.SharpSSH,   
Version=1.1.1.13, Culture=neutral, PublicKeyToken=null'.

the code that I'm use is like below :

SshTransferProtocolBase sshCp = new Scp(Tools.GlobalVarMeth.hostName, Tools.GlobalVarMeth.serverUserName);
sshCp.Password = Tools.GlobalVarMeth.serverUserpassword;
sshCp.Connect();

string localFile = Tools.GlobalVarMeth.applicationPath + "/" + fileName + ".csv";
string remoteFile = Tools.GlobalVarMeth.serverRemoteFilePath + "/" + fileName + ".csv";

sshCp.Put(localFile, remoteFile);
   
sshCp.Close();

Any one have any idea on this ? I will be really grateful !!!

Answer 1

It could be any number of things. Likely causes are:

• The assembly cannot be found
• An assembly that your assembly depends upon cannot be found
• The assembly is found but the type isn't in it
• The type's static constructor throws an exception

Your best bet is to use the Fusion log viewer to help diagnose it. Documentation is here:

http://msdn.microsoft.com/en-us/library/e74a18c4(v=vs.110).aspx

(FYI "Fusion" was the code name of the team that designed the assembly loading system; it is somewhat unfortunate that the code name ended up in the file name of the shipped product. The thing should have been called "AssemblyBindingLogViewer.exe" or some such thing.)

Answer 2

The answer of Eric Lippert perfectly describes the situation.

I just want to add a quick answer about a case which is usually not covered by help pages regarding this exception.

I've created a quick & dirty test project for some open source stuff (Akka.Net, to name it) and I name the project itself "Akka".

It perfectly builds, but at startup it throws it type load exception regarding a class in Akka.dll.

This is just because my executable (akka.exe) and the reference (akka.dll) have the same name. It took me a few minutes to figure this (I've began by things such as copy local, target platform, exact version... etc).

It's something very dumb but not forcibly the first thing which you will think (especially since I used nuget for dependancies), so I thought it could be interesting to share it : you will encounter TypeLoadException if your EXE and a dependancy have the same name.

Answer 3

I don't know how I managed this, but for some reason I had an old version of the DLL in GAC (Global Assembly Cache). Try looking for an old assembly there and remove it.