how to call a c++ function with wchar_t[] parameter

[Akademos]

Hi,
I've got a unmanaged C++ DLL which exports 1 function:

extern "C" bool GetDatabaseInfo( UINT uiBuffCnt,
                                 wchar_t wcDataSource[], wchar_t wcCatalog[],
                                 wchar_t wcUsername[], wchar_t wcPassword[] )

Now I've got to call this function from c#. I tried it this way:

[ DllImport( "..\\mydll.dll" ) ]
    internal static extern bool GetDatabaseInfo( uint uiBuffCnt,
                                                 ref string[] sDataSource,
                                                 ref string[] sCatalog,
                                                 ref string[] sUsername,
                                                 ref string[] sPassword
                                               );

string[] sDataSource = new string[1024], 
                 sCatalog    = new string[1024],
                 sUsername   = new string[1024],
                 sPassword   = new string[1024];
 GetDatabaseInfo( 1024, ref sDataSource, ref sCatalog, ref sUsername, ref sPassword );

But the call always fails. Can anyone give me a hint what i did wrong?

Thanks in Advance

Akademos

[RobAnd]

Do you realize that the sample you provided creates a total of 4096 strings? When you do a "new string[NN]" you are allocating memory for an array of NN strings.

Also, the C type of wchar_t is a wide character. Therefore, your C function takes an unsigned integer and 4 wide character arrays. The wide character arrays are usually single UNICODE strings.

In the C# application, prototype the function to take strings only (not string arrays) and it should be fine.

Hope that helps.

- Robert

[Akademos]

You're right, what a stupidy of mine.
This is the correct code:

[ DllImport( "..\\mydll.dll", CharSet=CharSet.Unicode ) ]
    internal static extern bool GetDatabaseInfo( uint uiBuffCnt,
                                                 string sDataSource,
                                                 string sCatalog,
                                                 string sUsername,
                                                 string sPassword
                                               );
                                               
//----------------------------------------------------------------------

		private void Page_Load(object sender, System.EventArgs e)
		{
		  
      string sDataSource = new string( ' ', 1024 );
      string sCatalog = new string( ' ', 1024 );
      string sUsername = new string( ' ', 1024 );
      string sPassword = new string( ' ', 1024 );
      try
      { 
        //sDataSource = sCatalog = sUsername = sPassword = "";         
        GetDatabaseInfo( 1024, m_sDataSource,m_sCatalog,m_sUsername,m_sPassword );
     }

But now I've go the problem that the returning strings a filled with '\0' behind the text when the given length is greater than the actual length.
Now i want to trime the returning string to a fitting size. How can I do that?

Thanks in Advance

Akademos