Great Difficulty calling c++ dll from c#

[David Buttigieg de Piro]

I am using c# 2010 and need to call a method in an old c++ dll

It keeps giving me the following error:
"Attempted to read or write protected memory. This is often an indication that other memory is corrupt."

The function I am trying to call in the dll is

void handle_str_ni(LPCSTR lpcstrCommandLine);

So far this is my code :

[DllImport((@"c:\Mydll.dll"), EntryPoint="handle_str_ni", SetLastError = true, CharSet = CharSet.Auto, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
 
public static extern void handle_str_ni([MarshalAs(UnmanagedType.LPStr)]string sString);
 
[MarshalAs(UnmanagedType.LPStr)]public String f1 = "getp p1";
 
private void button1_Click(object sender, EventArgs e)
{
   handle_str_ni(f1);
}
 
 

[wizardry]

try recompiling the old .dll with the new complier. that should take care of your errors. i've ran into that before when i switched ide's.

[David Buttigieg de Piro]

The dll is regularly compiled