Question

I am not sure why I am getting this error.
How can I dynamically set the error provider for a control?

if (errorList.Count == 0)
        {
            return true;
        }
        else
        {
            foreach (ErrorEntity ee in errorList)
            {
                if (ee.InError)
                {
                    Control[] ctl = this.Controls.Find(ee.FieldName, true);
                    if (ctl != null)
                    {
                        errorProvider.SetError(ctl[0], ee.ErrorMessage);
                    }
                }
            }
        }

Answer 1

My guess is that

this.Controls.Find(ee.FieldName, true);

is returning an empty collection, and not a null.
So when you check for null, you should also check for empty (ie: Count==0)