C# function Convert From Hijri to Georgian

C#

public string ConvertDateCalendar(DateTime DateConv, string Calendar, string DateLangCulture)
{
DateTimeFormatInfo DTFormat;
DateLangCulture = DateLangCulture.ToLower();
/// We can't have the hijri date writen in English. We will get a runtime error - LAITH - 11/13/2005 1:01:45 PM -

if (Calendar == "Hijri" && DateLangCulture.StartsWith("en-"))
{
DateLangCulture = "ar-sa";
}

/// Set the date time format to the given culture - LAITH - 11/13/2005 1:04:22 PM -
DTFormat = new System.Globalization.CultureInfo(DateLangCulture, false).DateTimeFormat;

/// Set the calendar property of the date time format to the given calendar - LAITH - 11/13/2005 1:04:52 PM -
switch (Calendar)
{
case"Hijri":
DTFormat.Calendar = new System.Globalization.HijriCalendar();
break;

case"Gregorian":
DTFormat.Calendar = new System.Globalization.GregorianCalendar();
break;

default:
return"";
}

/// We format the date structure to whatever we want - LAITH - 11/13/2005 1:05:39 PM -
DTFormat.ShortDatePattern = "dd/MM/yyyy";
return (DateConv.Date.ToString("f", DTFormat));
}