C struct to C# struct

[Alvaro Enriquez de Luna]

Hello everybody. I am trying to use in C# a dll developed in C. I am
founding problems with C structs. While my C struct does not include
anything related with char or char *, everyting works ok, but when I
introduce a char or char * variable in the struct, I obtain a message
like this:

"Method's type signature is not PInvoke compatible."

Here is my code in both languages:

***************
C CODE
***************
struct _struct
{
int inte;
double doub;
float floa;
char charac;

};

__declspec(dllexport) struct my_struct GiveMeStruct()
{
struct my_struct stru;

stru.inte=25;
stru.doub=3.141592;
stru.floa=0.02546f;
stru.charac='n';
return stru;

}

******************
C# CODE
******************
//////////////////////
Declaration:
//////////////////////

public struct my_struct
{
public int inte;
public double doub;
public float floa;
public char charac;
}

[DllImport("Resources/DLL/CCSS_DLL.dll")]
public static extern my_struct GiveMeStruct();

/////////////////////
Use: (i.e. after a button is pushed in a Form)
///////////////////

my_struct aux_estruct = DBManager.GiveMeStruct();

MessageBox.Show(aux_estruct.inte.ToString());
MessageBox.Show(aux_estruct.doub.ToString());
MessageBox.Show(aux_estruct.floa.ToString());
MessageBox.Show(aux_estruct.charac.ToString());

NOTE: Everything works until I add the 'charac' part in both sides, C
and C#.

Any ideas about how to do it? Thanks in advance.