I get the compile error when I call the method. Is there something different to do when passing an array as a parameter?

Here's the code I have now:

// server is defined elsewhere and is working just fine. One row is returned in ds
DataSet ds = server.GetDemoByPk(100);

// Two errors occur on the next line
ArrayList dso = ConvertField(ds.Tables["Demo"].Rows[0][10]);

// ConvertField is defined in the same class as the above code
ArrayList ConvertField(byte[] theData)
{
  ArrayList result = new ArrayList();
  return result;
}

Error 1:
The best overload method match for 'ConvertField(byte[])' has some invalid arguments.

Error 2:
Argument '1': cannot convert from 'object' to 'byte[]'

I tried casting the field to byte[], then got the following error on the same line:
An object reference is required for the nonstatic field, method, or property 'ConvertField(byte[])'

>And what line gives you the error message?