String Pointers in c#

Question

I have a windows form application in c#, that uses a function in c++. This was done using a c++ wrapper. However, the function requires the use of pointers and c# does not allow the use of pointers with string arrays. What can be done to overcome this? I have read up on using marshal but i am not sure if this is suitable for this case and if so how should it be integrated with my code. The following is the C# code:

 int elements = 10;
string [] sentence = new string[elements];

unsafe
{
    fixed (string* psentence = &sentence[0])
    {
        CWrap.CWrap_Class1 contCp = new CWrap.CWrap_Class1(psentence, elements);
        contCp.getsum();
    }
}

c++ function declaration: funct::funct(string* sentence_array, int sentence_arraysize)

c++ wrapper: CWrap::CWrap_Class1::CWrap_Class1(string *sentence_array, int sentence_arraysize) { pcc = new funct(sentence_array, sentence_arraysize); }

@jhyap If you're saying C# doesn't have pointers.. it most certainly does. Not quite as flexible as other languages.. but they still exist. — Simon Whitehead
– Simon Whitehead, Commented Nov 14, 2013 at 4:43
@jhyap: are you kidding? Put C# pointers into google and spend some time reading — zerkms
– zerkms, Commented Nov 14, 2013 at 4:45
Include the C++ function declaration in your question, otherwise an answer is random guessing. — William
– William, Commented Nov 14, 2013 at 4:45

joe · Accepted Answer · 2013-11-14 06:31:19Z

1

If I understand you correctly you want to call a C function with string as parameters.
For this, you usually use PInvoke (platform invoke), which uses marshalling under the hand.

This example takes a string and returns a string.

[DllImport(KMGIO_IMPORT,CallingConvention=CallingConvention.Cdecl)]     
//DLL_EXPORT ushort CALLCONV cFunction(char* sendString, char* rcvString, ushort rcvLen);
private static extern UInt16 cFunction(string sendString, StringBuilder rcvString, UInt16 rcvLen);

public static string function(string sendString){
    UInt16  bufSize = 5000;
    StringBuilder retBuffer = new StringBuilder(bufSize);
    cFunction(sendString, retBuffer, bufSize);
    return retBuffer.ToString();
}

answered Nov 14, 2013 at 6:31

joe

8,70410 gold badges60 silver badges84 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Mahol25 Over a year ago

The main point in joes code here is the use of StringBuilder. Normal strings in .NET are immutable by design, which is why a pointer to such a string is not a great idea to pass to code that wants to manipulate that string. StringBuilder is different however,since it by design acts more like a buffer to a piece of memory that can be modified making it modifiable also from unmanaged code, an later can be used to produce an immutable string in .NET. Check out the dox on StringBuilder and pinvoke (pinvoke.net) and you should get some ideas.

Collectives™ on Stack Overflow

String Pointers in c#

1 Answer 1

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related