Does not work with Dllimport

[davidwillian252]

I have a csharp exe ([DllImport("DLLOK.dll", SetLastError = true)]
public static extern bool FunctionOne(string hookprocess);
[DllImport("DLLOK.dll", SetLastError = true)]
public static extern bool FunctionTwo(IntPtr hWnd);)
which imports a native dll in c++(), when I process the compiled exe in the packer and run the generated exe, it returns an exception System.BadImageFormatException App.Form1.FunctionOne. If I comment out the DllImport and it doesn't load the DLL, the exe generated by the packer works correctly.