上面的答案是正确的，但是如果你只想把整天作为整数，并且愿意放弃约会的时间部分，那么可以考虑:

(EndDate.Date - StartDate.Date).Days

同样假设StartDate和EndDate是DateTime类型。

我认为这会达到你的目的:

DateTime d1 = DateTime.Now;
DateTime d2 = DateTime.Now.AddDays(-1);

TimeSpan t = d1 - d2;
double NrOfDays = t.TotalDays;

得到两个日期之间的差值，然后从下面得到日期:

int total_days = (EndDate - StartDate).TotalDays

// Difference in days, hours, and minutes.

TimeSpan ts = EndDate - StartDate;

// Difference in days.

int differenceInDays = ts.Days; // This is in int
double differenceInDays= ts.TotalDays; // This is in double

// Difference in Hours.
int differenceInHours = ts.Hours; // This is in int
double differenceInHours= ts.TotalHours; // This is in double

// Difference in Minutes.
int differenceInMinutes = ts.Minutes; // This is in int
double differenceInMinutes= ts.TotalMinutes; // This is in double

你也可以得到秒、毫秒和滴答的差异。

你可以试试这个

EndDate.Date.Subtract(DateTime.Now.Date).Days

date格式为"dd/MM/yyyy"

  string[] d1 = txtFromDate.Values.Split('/');
  string[] d2 = txtToDate.Values.Split('/');

  DateTime FrmDt = new DateTime(Convert.ToInt32(d1[2]), Convert.ToInt32(d1[1]), Convert.ToInt32(d1[0]));
  DateTime ToDt = new DateTime(Convert.ToInt32(d2[2]), Convert.ToInt32(d2[1]), Convert.ToInt32(d2[0]));

  TimeSpan TDiff = ToDt.Subtract(FrmDt);
  String DaysDiff = TDiff.TotalDays.ToString();