date type

As well as Convert.ToDateTime, there are a number of other static methods in the .NET Framework which can convert an appropriate string into a DateTime:

DateTime.Parse
DateTime.ParseExact
DateTime.TryParse
DateTime.TryParseExact

For information on using these methods, check this link:

http://msdn.microsoft.com/en-us/library/system.datetime(v=vs.110).aspx

Try this...

string strDate = "21-07-2006";
DateTimeFormatInfo dtfi = new DateTimeFormatInfo();
dtfi.ShortDatePattern = "dd-MM-yyyy";
dtfi.DateSeparator = "-";
DateTime objDate = Convert.ToDateTime(strDate, dtfi);
MessageBox.Show(objDate.ToShortDateString());