Hi,

I have a C function that's declared like this:

int my_function( BSTR *input, BSTR *output ) ;

Here BSTR is the windows BSTR type.
The output argument is allocated within my_function.

I declared it in my C# class as follows:

[DllImport("mydll.dll")]
public static extern int my_function( StringBuilder in, StringBuilder
out);

and when I run my program, I get the exception:

Object reference not set to an instance of an object:

My class does the following:

StringBuilder in, out;
in = new StringBuilder(100);
out = new StringBuilder(100);

int retval = my_function( in, out );

First, what does this error message mean?
Second, are my argument types wrong?  Since my_function() allocates
the value to be returned via the out argument, perhaps something else
has to be done.

Thanks,

Ted