How to compare Time variables? - vb.net

Question

I have 3 variables of type DateTime or string type, in the form hh:mm:ss.
For example:
dT1="00:00:00"
dT2="20:59:59"
dT3="18:04:21"
How can I perform the following comparison?
dT1<= dT3 <= dT2 ??

Answer 1

Your example show String not DateTime. I put your strings in and array called TimeStrings. Then I created a List of TimeSpan. Looping through the strings I split each string on the colon, then created a new TimeSpan and added it to the list. I used the .Max method of the list to get the highest value in the list.
Private Sub OpCode()
'Constructor TimeSpan(Int32, Int32, Int32)
Dim dT1 = "00:00:00"
Dim dT2 = "20:59:59"
Dim dT3 = "18:04:21"
Dim TimeStrings = {dT1, dT2, dT3}
Dim Spans As New List(Of TimeSpan)
For Each s In TimeStrings
Dim Splits = s.Split(":"c)
Dim span As New TimeSpan(CInt(Splits(0)), CInt(Splits(1)), CInt(Splits(2)))
Spans.Add(span)
Next
Dim HighestValue = Spans.Max
MessageBox.Show(HighestValue.ToString)
End Sub

Answer 2

You can use the TimeSpan.Parse(), ParseExact(), TryParse() or TryParseExact() to convert the string to a TimeSpan value. The comparison is straightforward after that:
Add your string values to a collection (an Array or List of strings).
Dim dTs As String() = {"00:00:00", "23:59:59", "20:59:59", "23:10:21", "18:04:21"}
Dim max As TimeSpan = dTs.Select(
Function(s) TimeSpan.ParseExact(s, "hh\:mm\:ss", CultureInfo.InvariantCulture)).Max()
max will be 23:59:59
Of course you can order the TimeSpan value, in ascending order here:
Dim orderedTimeSpans =
dTs.Select(Function(s) TimeSpan.ParseExact(s, "hh\:mm\:ss", CultureInfo.InvariantCulture)).
OrderBy(Function(ts) ts).ToList()
orderedTimeSpans.ForEach(Sub(ts) Console.WriteLine(ts))
Which prints:
00:00:00
18:04:21
20:59:59
23:10:21
23:59:59
With TryParseExact(), if you're not sure whether the format is may not be correct (possibly, because the source of the values is not reliable - User input, for example):
Dim parsed As TimeSpan
Dim max As TimeSpan =
dTs.Select(Function(s) TimeSpan.TryParseExact(s, "hh\:mm\:ss",
CultureInfo.InvariantCulture, parsed)).Max(Function(t) parsed)
This also returns 23:59:59.
If one of the values cannot be parsed, it won't be evaluated by the Max() method.
E.g., if this is the input string "23.59:59", InvariantCulture and the format specified won't allow to return a valid TimeSpan, so the max value will be 23:10:21 instead.
The same, using TryParseExact(), but in extended form (using a loop):
Dim maxValue As TimeSpan = New TimeSpan()
Dim parsed As TimeSpan = New TimeSpan()
For Each value As String In dTs
If TimeSpan.TryParseExact(value, "hh\:mm\:ss", CultureInfo.InvariantCulture, parsed) Then
maxValue = If(TimeSpan.Compare(maxValue, parsed) > 0, maxValue, parsed)
End If
Next

Answer 3

You can try something like this:
Dim dT1 As DateTime = New DateTime(2020, 1, 1, 0, 0, 0) ' 00:00:00
Dim dT2 As DateTime = New DateTime(2020, 1, 1, 20, 59, 59) ' 20:59:59
Dim dT3 As DateTime = New DateTime(2020, 1, 1, 18, 04, 21) ' 18:04:21
If dT1 <= dT3 <= dT2 Then
'your code
End If
Hope, it helps :)