Here is my final piece of code if someone needs it. It also extends the width of the column a little bit after Autofit.

        int i = 1;
        while (i <= ws.UsedRange.Columns.Count)
        {
            try
            {
                ws.Columns[i].AutoFit();                
            }
            catch
            {
                try
                {
                    ws.Columns[i].AutoFit();
                    ws.Columns[i].ColumnWidth = ws.Columns[i].ColumnWidth + 5;                     
                }
                catch
                {
                    ws.Columns[i].Width = 255;                       
                }
            }
            i++;
        }