var testDate = startDate.AddDays(i);
string dateOnlyString = testDate.ToString("dd-MM-yyy");
"dd-MM-yyy"
this will be the Date Format of the output string, You can choose the format as per your requirements.
You can use the following also for formatting:
dateOnlyString = d.ToString("M/d/yyyy"); // "3/9/2008"
dateOnlyString = d.ToString("MM/dd/yyyy}"); // "03/09/2008"
// day/month names
dateOnlyString = d.ToString("ddd, MMM d, yyyy}"); // "Sun, Mar 9, 2008"
dateOnlyString = d.ToString("dddd, MMMM d, yyyy}"); // "Sunday, March 9,2008"
// two/four digit year
dateOnlyString = d.ToString("MM/dd/yy}"); // "03/09/08"
dateOnlyString = d.ToString("MM/dd/yyyy}"); // "03/09/2008"