Confusion when comparing StartDate and EndDate in asp.net

I am a bit confused when comparing StartDate and EndDate in my asp.net app.

EndDate:    10/1/2011
StartDate:  9/30/2011

The if statement below returns true, based on t开发者_如何学JAVAhe date values above.

If strEndDate < strStartDate Then

I would think the If statement shoudl return false. The concept is supposed to be that if EndDate is earlier than StartDate, display an error message.

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I'm assuming that since your variables are called strEndDate and strStartDate that they're strings, not DateTimes. Since they're strings, and since '1' < '9' (the first characters in the strings), strEndDate is indeed "less than" strStartDate.

Convert the values to DateTime before comparing:

If DateTime.Parse(strEndDate) < DateTime.Parse(strStartDate) Then
    '...
End If

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If those are DateTime variables, that code should evaluate to true. If not, you should convert them to DateTime.

DateTime start = DateTime.Parse(strStartDate);
DateTime close = DateTime.Parse(strEndDate);

if (close > start)
    //do something

You can also compare them like this:

if ((close - start).TotalDays > 0)
    //do something

As Rick Schott pointed out, you can also use DateTime.Compare

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You should be using DateTime.Compare.

Dim date1 As Date = DateTime.Parse(strStartDate)
Dim date2 As Date = DateTime.Parse(strEndDate)
Dim result As Integer = DateTime.Compare(date1, date2)
Dim relationship As String

If result < 0 Then
   relationship = "is earlier than"
ElseIf result = 0 Then
   relationship = "is the same time as"         
Else
   relationship = "is later than"
End If

Console.WriteLine("{0} {1} {2}", date1, relationship, date2)
' The example displays the following output:
'    8/1/2009 12:00:00 AM is earlier than 8/1/2009 12:00:00 PM

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Don't compare them as strings, compare them as dates.