VB.NET: Code does not check if control exists in panel

Question

My code :

Rs.Open("Select * From Notifications",Con)
If Not Rs.EOF Then
   For i=0 to Rs.RecordCount -1
     Dim Label As New Label
     With Label
        .Name = String.Format("Label_{0}",Rs("Id").Value.ToString)
        .Text = Rs("Notification").Value.ToString
     End With
     If Not Panel.Controls.Contains(Label) Then
        Panel.Control.Add(Label)
     End If
     Rs.MoveNext()
   Next
End If

But this always adds control to panel, the following code line is not executed correctly: (If Not Panel.Controls.Contains(Label) Then)

This code works in timer.

Solution 1

Function CntrlExistsIn(ctrlName as String, parent as Control) as Boolean
    Dim bResult as Boolean = False

    For Each elem as Control In parent.Controls
        If elem.Name = ctrlName Then
            bResult = True
            Exit For
        End If
    Next

    Return bResult
End Function

The above function is to check whether control(label) exists in Panel or not.

Solution 2

There is another way to reduce your code like below

 If panel1.Controls.Find(Label.Name, True).Length = 0 Then
    panel1.Control.Add(Label)
 End If  

Controls.Find(controlName,True/False)------True/False is for to check in child controls of specified control

Comments

[SysDragon]

I dont understand what do you want

[andy]

Check "Id" and "Notification"........... Its coming different for each loop

[Ekrem OĞUL]

this code work in timer and check a minute. if notification is show in panel then i dont want to add new. if not show notification(is new) then i want to add to panel with new control label.

[Ekrem OĞUL]

Thanks SysDragon. I Tray If Not Panel.Controls.Contains(Label) Then but search in controls with control name is working. thank you so much.

[Konrad Rudolph]

This code can be shortened by almost half by removing the useless variable and returning immediately.

[SysDragon]

@KonradRudolph I know, but Im used to do bigger functions and I prefer to follow best programming practices. Only one return is clearer.

[Konrad Rudolph]

@SysDragon No no, it’s the other way round. If you want to follow best practices, make your functions smaller. Also, “single return” has never been a best practice, it’s a completely misunderstood concept.

[SysDragon]

@KonradRudolph Well, looks like it's a very controversial topic. Theres people and experts saying both things. =/

[Konrad Rudolph]

@SysDragon No, it’s not at all controversial, simply a misunderstanding. There’s an explanation here: programmers.stackexchange.com/a/118793/2366, and here are some reasons to explain why, even though it might make sense in C, it never makes sense in languages such as VB: programmers.stackexchange.com/a/118717/2366

[SysDragon]

@KonradRudolph Thanks for the information. Very interesting. Ill consider changing my practice for small or even medium functions.