CODEWITHSUNDEEP
c#pinvokemarshalling
ant2009
ant2009

Reputation: 22696

equivalent char* in C#

I have a dll that is written in c++. And I am p/invoking to call the functions.

I have this c++ declaration.

int dll_registerAccount(char* username, char* password);

I have done this dllimport declaration:

[DllImport("pjsipDlld")]
static extern int dll_registerAccount(IntPtr username, IntPtr password);

Would my DllImport be the equivalent to the c++ using IntPtr?

Many thanks for any advice,

Upvotes: 4

Views: 23529

Answers (5)

Yuresh Karunanayake
Yuresh Karunanayake

Reputation: 567

[DllImport("DLL loction"), EntryPoint = "dll_registerAccount",
    CallingConvention = CallingConvention.Cdecl)]
[return : MarshalAs(UnmanagedType.I4)]
static extern int dll_registerAccount(
    [MarshalAs(UnmanagedType.LPStr)]string username,
    [MarshalAs(UnmanagedType.LPStr)]string password);
  • cdecl is the default calling convention for C and C++ programs,
  • refer these doc for more information.

Upvotes: 2

Steztric
Steztric

Reputation: 2942

Be aware of calling conventions, this tripped me up. In my case I need to call a C++ DLL but with C-style exports, which uses the cdecl calling convention. If you have the luxury of having the source Visual Studio Solution, go to Properties -> C/C++ -> Advanced and find it under "Calling Convention". This fix it for me:

[DllImport(DllName, CharSet = CharSet.Ansi, CallingConvention = CallingConvention.Cdecl)]
// bool MyFunction(char* fileName) <-- From the DLL
static extern bool MyFunction(string fileName);

Upvotes: 2

ParmesanCodice
ParmesanCodice

Reputation: 5035

StringBuilder for char*, since the length is unknown?

[DllImport("pjsipDlld")]
static extern int dll_registerAccount(StringBuilder username, StringBuilder password);

Upvotes: 1

Stephen Martin
Stephen Martin

Reputation: 9645

    [DllImport("pjsipDlld", CharSet = CharSet.Ansi)]
    static extern int dll_registerAccount(string username, string password);

Upvotes: 1

Blindy
Blindy

Reputation: 67524

The C# way of doing this is by letting the marshaler handle the char* stuff while you work with a string:

[DllImport("pjsipDlld")]
static extern int dll_registerAccount(
    [MarshalAs(UnmanagedType.LPStr)]string username,
    [MarshalAs(UnmanagedType.LPStr)]string password);

Replace LPStr with LPWStr if you're working with wide chars.

Upvotes: 27

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