如何在C＃中减去两个Datetime值？

Question

I want to subtract two Datetime values. I collected them separately from the form and concatenate it in C#. The result shows in Hour format in textbox like "23:00".

Here is what I tried:

string start = StartDateTxtBox.Text+" "+StartHourDrop.Text+":"+StartMinuteDrop.Text+":00";
string End = EndDateTxtBox.Text + " " + EndHourDrop.Text + ":" + EndMinuteDrop.Text + ":00";

DateTime allstart = DateTime.Parse(start);
DateTime allEnd = DateTime.Parse(End);

Int32 MinuteDiff = Convert.ToInt32(allEnd.Subtract(allstart).TotalMinutes);
Int32 Hour = MinuteDiff / 60 / 24;
DateTime conversiontotime = System.Convert.ToDateTime(Hour);
LastID.Text = conversiontotime.ToString();

But it doesn`t work.

Is there another (easy) way to do this, or can anybody tell me what the problem in my code is?

Answer 1

    DateTime allstart = DateTime.Parse("03/04/2015 09:15");
    DateTime allEnd = DateTime.Parse("03/04/2015 09:37");
    TimeSpan tsdiff = allEnd - allstart;
    LastID.Text = tsdiff.ToString();