Checking to see if a from is open

[Jay1b]

Hi

I have a timer event (every second) that checks to see if a condition is true, if so then it raises a form. Currently the program just raises the form every second - which is obviously annoying.

I would like to check if the form is currently running then only create a new instance of it, if it isnt. The code below is in a procedure that is called from the timer event

            Dim FrmAllowDis As New FrmAllowDis
            FrmAllowDis.Text = ThisProcess.ProcessName
            'Display the form
            If FrmAllowDis.ShowDialog() = System.Windows.Forms.DialogResult.Yes Then
            End If

Could someone tell me what i am doing wrong pls?

Thanks.

 

[stustarz]

Hi again, ive dealt with this before, whereby i wanted to limit the forms instance to 1. Basically i made the following changes to the form i wanted to limit:

if you had 2 forms: Form1 and Form2 and only wanted to show one instance of Form2 no matter how many times a show button was clicked:

Add this to the top of the form2 class:

Private Shared objFrmInstance As Form2

Change the default Public Sub New() code to:

Private Sub New()

This function goes inside the Form2 Class

'If an instance doesnt already exist then set the instance to New Form1
'when called, if an instance isnt already available the calling code can
'create a new instance of the form
    Public Shared Function GetInstance() As Form2
        If objFrmInstance Is Nothing Then
            objFrmInstance = New Form2
        End If
        Return objFrmInstance 
    End Function

Add a button to Form1 and on its click event:

        Dim frmForm2 As Form2 = Form2.GetInstance()
        varForm2.Show()

 

[Jay1b]

Tried, tested and works beautifully thank you!

Next question: How did you ever think of that?

 

[Jay1b]

Slight Problem:

Once i close the frame i cant ever reopen it without an error.

 

[stustarz]

Oooops my mistake: You need to add the following code to overide the Forms Closing event so that the instance isnt destroyed, just hiden:

  Protected Overrides Sub OnClosing(ByVal e As CancelEventArgs)
    e.Cancel = True
    Me.Hide()
  End Sub

 

[Joe Mamma]

Tried, tested and works beautifully thank you!

Next question: How did you ever think of that?

its typical Design Pattern - Factory

by the way, the proper solution for your problem is:

Protected Overrides Sub OnClosing(ByVal e As CancelEventArgs)
objFrmInstance = nothing
End Sub

 

[Jay1b]

Thank you!