Working With DataAdapter Values

 I have done some reading on the dataadapter class,  but do not have a good handle on how to work  with dataadapter after it has been filled by a dataset.  For instance,  should I use an if statement such as this to update the value in the dataadapter?
 
if (dsSunbelt.Tables[0].Columns[39].Equals(""))
        {
            DataRow drUpdate = dsSunbelt.Tables[0].Columns[39].Equals(DateTime.Now);
        }
        
I am sure it is not hard to see what I am doing, and I hope that I am missing something small, but how do I isolate a dataadapter value to update in the corresponding database?