exporting function with parm pointer to char string

[Angel]

I'm exporting a C-style function call with this syntax:

int getDate(char *date);

I'm trying to export to my c# app like this:

[DllImport("C:\\zm7\\Developm\\DLL\\W32.DLL")]
public static extern int getDate(System.IntPtr ptr);
public void getDate()
{
IntPtr ptr = new IntPtr();
string str = "";
getDate(ptr); //// ERROR: Object reference not set to an instance of
an object
str = Marshal.PtrToStringAnsi(ptr);
}

What Am I doing wrong?

Thanks.

[Mattias Sjögren]

>What Am I doing wrong?

You're passing in a null pointer. Try it this instead

public static extern int getDate(StringBuilder ptr);

Mattias

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Mattias Sjögren [MVP] mattias @ mvps.org
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[Angel]

That worked.

Thank you.

"Mattias Sjögren" <ma********************@mvps.org> wrote in message
news:uj**************@TK2MSFTNGP10.phx.gbl...

What Am I doing wrong?

You're passing in a null pointer. Try it this instead

public static extern int getDate(StringBuilder ptr);

Mattias

--
Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.