Send value to parent then close child form, on event - vb.net

Question

I have a parent form with a combobox populated from a database, from which the user can select. The last value in the combo box is "add new", if the user selects this, a child form opens for the user to add a new value to the database. I have a button press event to add this value to the database, send the new return value to the parent and close the form. The parent should then select the new value from it's combo box and wait for the user to perform another action.
However, the code to send the return value to parent and close the form isn't working correctly. I hide the child, then call a function on it with the parent to access the return value. At this point the child form shows and the code stops before it runs another hide or close.
How can I fix this (code below)?
Parent Combobox event:
Private Sub cmbLocations_SelectedIndexChanged(sender As System.Object, e As System.EventArgs) Handles cmbLocations.SelectedIndexChanged
If Not cmbLocations.SelectedIndex = -1 Then
If cmbLocations.SelectedIndex = cmbLocations.Items.Count - 1 Then
If diaAddLocation.IsAccessible = False Then diaAddLocation.Activate()
diaAddLocation.RequestSender = Me
diaAddLocation.ShowDialog()
FillLocations()
cmbLocations.SelectedIndex = LocationFromLocationName(diaAddLocation.formresult)
diaAddLocation.Close()
diaAddLocation.Dispose()
Else
bttYes.Enabled = True
End If
End If
End Sub
Child Button Press and Return value function
Public Sub bttAddLOCtoDatabase_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles bttAddLOCtoDatabase.Click
Dim LocationToBeAdded As String
LocationToBeAdded = "'" & TextBox1.Text & "'"
AddLocation("'" & textbox1.Text & "'")
FormResult = textbox1.Text
GetLocations()
frmFieldMaster.InitialiseNewParameter()
Me.Hide()
End Sub
Public Function Result() As String
Return FormResult
End Function
EDIT:
code with Steve's solution implemented:
Public Sub bttAddLOCtoDatabase_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles bttAddLOCtoDatabase.Click
Dim LocationToBeAdded As String
LocationToBeAdded = "'" & TextBox1.Text & "'"
AddLocation("'" & textbox1.Text & "'")
FormResult = textbox1.Text
GetLocations()
frmFieldMaster.InitialiseNewParameter()
DialogResult = Windows.Forms.DialogResult.OK
'me.Hide()
End Sub
Public Function Result() As String
Return FormResult
Me.Close()
End Function
Private Sub cmbLocations_SelectedIndexChanged(sender As System.Object, e As System.EventArgs) Handles cmbLocations.SelectedIndexChanged
Dim ValueTaken As Boolean = False
If Not cmbLocations.SelectedIndex = -1 Then
If cmbLocations.SelectedIndex = cmbLocations.Items.Count - 1 Then
Using diaaddlocation = New diaAddLocation
diaaddlocation.requestsender = Me
If DialogResult.OK = diaaddlocation.showdialog Then
FillLocations()
cmbLocations.SelectedIndex = LocationFromLocationName(diaaddlocation.result)
diaaddlocation.close()
ElseIf DialogResult.Cancel = diaaddlocation.showdialog Then
cmbLocations.SelectedIndex = -1
End If
End Using
Else
bttYes.Enabled = True
End If
End If
End Sub
When I run the code it enters IF DialogResult.OK... and opens the child. Then when I close the child the parent runs the next two lines of code and get the result from the child. After this the parent runs the line IF DialogResult.OK... again and stops with the child open. The code never reaches the diaaddlocation.close line.

Answer 1

You don't need all of this. You could try something like this
If cmbLocations.SelectedIndex = cmbLocations.Items.Count - 1 Then
Using diaAddLocation = new diaAddLocation()
diaAddLocation.RequestSender = Me
if DialogResult.OK = diaAddLocation.ShowDialog() then
FillLocations()
cmbLocations.SelectedIndex = LocationFromLocationName(diaAddLocation.formresult)
End If
End Using
Else
.....
This requires the DialogResult property for bttAddLOCtoDatabase set to DialogResult.OK and the child form AcceptButton property set to bttAddLOCtoDatabase. Now you could remove the Hide() call inside the bttAddLOCtoDatabase_Click method
This works because, until you don't exit the Using statement, your child form is still available to read its properties (results)
EDIT: Not related to the main problem, but these lines are wrong:
ElseIf DialogResult.Cancel = diaaddlocation.showdialog Then
cmbLocations.SelectedIndex = -1
you should go with
Using diaAddLocation = new diaAddLocation()
diaAddLocation.RequestSender = Me
Dim dr = diaAddLocation.ShowDialog()
if dr = DialogResult.OK then
....
else if dr = DialogResult.Cancel then
....
end if

Answer 2

I don’t understand what is issue but if you are not getting value of “FormResult”
It doesn’t matter if you close from but it will be better to set DialogResult before closing it, cause you are showing it as dialog (showdialog)
Verify that diaAddLocation is instance of you window not the window class directly
If name of you form is frmdiaAddLocation then do not use it like
frmdiaAddLocation.showdialog
use it like
Dim diaAddLocation AS frmdiaAddLocation = New frmdiaAddLocation()
diaAddLocation.ShowDialog()
only using like this way will provide you result value