Combo boxes will not calculate when selected

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So this is causing me some problems, i have 2 comboxes that are populated on form load with hours for a start time and an end time to a work shift, once combo1 time and combo2 time is selected the time difference in hours should be displayed in a label, but it lets me select but only displays the hours as 00:00:00 can anyone see what i have done wrong please its probably something so simple i can no longer see, im still a vb beginner so any advice would be helpful, thanks

What I have tried:

my code so far is :

populate the combos on load
'Set the Start Time Value
Dim start As DateTime = DateTime.ParseExact("00:00", "HH:mm", Nothing)
'Set the End Time Value
Dim [end] As DateTime = DateTime.ParseExact("23:59", "HH:mm", Nothing)
'Set the interval time
Dim interval As Integer = 15
'List to hold the values of intervals
Dim lstTimeIntervals As New List(Of String)()
'Populate the list with 15 minutes interval values
Dim i As DateTime = start
While i <= [end]
ComboBox1.Items.Add(i.ToString("HH:mm tt"))
ComboBox2.Items.Add(i.ToString("HH:mm tt"))
i = i.AddMinutes(interval)
End While
Then

Private Sub ComboBox2_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ComboBox2.SelectedIndexChanged

Dim duration As New TimeSpan()
Dim MyVariable1 As TimeSpan
Dim MyVariable2 As TimeSpan

MyVariable2 = ComboBox2.SelectedValue()
MyVariable1 = ComboBox1.SelectedValue()

duration = MyVariable2.Subtract(MyVariable1)

Label3.Text = duration.ToString

End Sub

Posted 5-Mar-18 11:46am

Member 8365433

Updated 5-Mar-18 12:37pm

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an0ther1 · Answer 1 · 2018-03-05T12:38:00

Firstly, name your controls with descriptive names, even if it is a test application, it takes a little more time but will always save you time in the long run.
Secondly, learn how to use a debugger, you will learn much more from debugging than pretty much anything else, the following links will help;
Debugger Basics | Microsoft Docs[^]
Navigating through Code with the Debugger[^]
In regards to your question, the following will help;

VB

' Use Date object instead of TimeSpan to get your values
Dim datStart as New Date
Dim datEnd as New Date
' Convert the values from the ComboBox
' NOTE: Selected Value will not be valid unless you set the Value member, hence use Text property
datStart = DateTime.ParseExact(ComboBox1.Text, "HH:mm tt", Nothing)
datEnd = DateTIme.ParseExact(ComboBox2.Text, "HH:mm tt", Nothing)
' A timespan is returned by arithmetic operations on DateTime objects
Dim tsDuration as New TimeSpan()
tsDuration = datEnd - datStart

Hope this helps

Kind Regards