Call a D7 dll from C#

[Jurandi 1]

Hello everyone.
I have a dll made in delphi 7 where the parameters are of type PChar.
Calling it in a delphi program works ok.
How to declare and use it in a C # program.
Ex delphi dll:

Function Mostra_Msg (Parmsg: PChar): LongBool; export; // stdcall
begin
  Result: = True;
  ShowMessage ('String Passed =' + Strpas (parmsg));
end;

Thank you.

Edited October 19, 2020 by Jurandi
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[David Heffernan 2345]

What calling convention is the function? If it is register then that is a problem. Make sure it is stdcall. 

 

A websearch for pinvoke will tell you how to call this function. 

[Remy Lebeau 1393]

Assuming the calling convention of the DLL function is stdcall, then the correct PInvoke declaration in C# would be as follows:

[DllImport("my.dll", CharSet = CharSet.Ansi)]
static extern bool Mostra_Msg (string Parmsg);

Alternatively:

[DllImport("my.dll")]
static extern bool Mostra_Msg ([MarshalAs(UnmanagedType.LPStr)]string Parmsg);

 

[Jurandi 1]

Hello Remy.
Thank you very much for the examples.
Both worked well.
Have a good week.
Hugs.

 

Edited October 19, 2020 by Jurandi