The Compact Framework doesn't support Assembly.GetEntryAssembly to determine the launching .exe. You can instead P/Invoke the native GetModuleFileName function like so:-
byte[] buffer = new byte[MAX_PATH * 2];
int chars = GetModuleFileName(IntPtr.Zero, buffer, MAX_PATH);
if (chars > 0)
{
string assemblyPath = System.Text.Encoding.Unicode.GetString(buffer, 0, chars * 2);
}
Where MAX_PATH is defined in the Windows CE headers as 260. The P/Invoke declaration for GetModuleFileName looks like this:-
[DllImport("coredll.dll", SetLastError = true)]
private static extern int GetModuleFileName(IntPtr hModule, byte[] lpFilename, int nSize);
The function expects a HMODULE - a handle to a native module. However passing IntPtr.Zero here indicates we want the module which created the process which is our .exe. This code will always return the path of the calling .exe regardless of if it is in a utility dll, or even a GAC assembly located in the \Windows folder.