Marshalling in C # (Passing a structure to an unmanaged type)

Question

I have a C ++ dll that provides the following function

long func(struct name * myname)
{
     strcpy(myname->firstname,"rakesh");
     strcpy(myname->lastname,"agarwal");
     return S_OK;
}

struct name
{
    char firstname[100];
    char lastname[100];
}

I want to call this function from a C # application, so I do the following:

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
unsafe public struct name
{
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst=100)]
    public string firstname;
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 100)]
    public string lastname;
} ;


[DllImport("C++Dll.dll")]
public unsafe static extern long func(name[] myname);

name[] myname = new name[1];
func(myname);

The application works successfully. When the C # .exe application is launched, the function func()is called successfully, and it can fill in the fields successfully inside the dll. But when the function returns to the application of C #, the variable mynameis still encodes zero values for structure fields ( firstnameand lastname).

Please suggest changes so that I can fill in the values ​​of the fields myname(so that after the function completes, the func()variable myname->firstnamecontains "rakesh" and myname->lastnamecontains "agarwal".

Note: StringBuilder cannot be used inside a structure.

Answer 1

. PInvoke ref . ref CLR , , .

[DllImport("C++Dll.dll")]
public unsafe static extern long func(ref name myname);

, interop, PInvoke (). C ( , , ) # VB.Net. , .

Answer 2

public unsafe static extern long func(ref name myname) :

name myname = new name();
func(ref myname);

, , .