You should be able to read the GUID attribute of the assembly via reflection. This will get the GUID for the current assembly
Assembly asm = Assembly.GetExecutingAssembly();
var attribs = (asm.GetCustomAttributes(typeof(GuidAttribute), true));
Console.WriteLine((attribs[0] as GuidAttribute).Value);
You can replace the GuidAttribute with other attributes as well, if you want to read things like AssemblyTitle, AssemblyVersion, etc.
You can also load another assembly (Assembly.LoadFrom and all) instead of getting the current assembly - if you need to read these attributes of external assemblies (for example, when loading a plugin).