Converting control type in a single function

Question

Hi

Rather than have a collection of functions to process data based on the control type that is passed to it, im wondering if its at all possible to convert an object to a specific control so that i can initial a Dim as the control type? Might be better for an example.. Lets say i have a range of controls that will all require the use of a function, these controls will be-

TextBox, Label, ComboBox, DataGrid, ListBox.

Each control type shares some common properties but not all. Here is an example of that id like to construct, its obviously not valid because its what im trying to achieve-

Function ProcessData(ByVal _control As Control) As String

Dim _C as Control = Nothing

Select Case _control.GetType()
   Case GetType(TextBox)
      _C = CType(_control, TextBox)

   Case GetType(Label)
      _C = CType(_control, Label)

   Case GetType(ComboBox)
      _C = Ctype(_control.ComboBox)

Return _C.Text

End Function

So the result i am after is no matter what control is passed to the function, i can assign the controls type to _C so that i can access the control Type properties relative to the Control being passed. If a TextBox is passed then _C As TextBox, if a ComboBox is passed then _C As ComboBox etc etc.

Is this achievable?

Thanks

Answer 1

Hi

Its not valid from the persepective of the control conversion being a true type conversion. for example:

Label, Textbox & ComboBox controls share mostly the same properties but a ComboBox has additional properties relating to its DropDown. By using the code example i provided, I can successfully convert _C control to a ComboBox but the specific ComboBox properties are not available because the the original Dim is set as Control. I was hoping that there would be a way to specifically set the Control as a type so that it would become its intended control type like _C.Type = Combobox or something like that.

I am using the code that i provided but can only access properties that are shared between the control types and cannot access anything that is control specific

Thanks

Answer 2

Hi

They are not special properties, they are control based properties. I dont think what i was looking to do was achievable which was to convert the passing control to its native control type instead of assign a type to it.

I have create a range of separate functions now in a class that operate in the same way but specifically for controls-

Public Class Validate

Public Sub New()
End Sub

Friend Function ValidateText(ByVal C As TextBox) As String
   'get my control specific data here
Return  ProcessData(NewVal, OldVal)
End Function

Friend Function ValidateCombo(ByVal C As ComboBox) As String
   'get my control specific data here
Return  ProcessData(NewVal, OldVal) 
End Function

Friend Function ValidateLabel(ByVal C As Label) As String
  'get my control specific data here
Return  ProcessData(NewVal, OldVal) 
End Function

Private Function ProcessData(ByVal Newvalue As String, OldValue As String) As String
   'Do the data validation here
   Return result
End Function

End Class

At least this way, in my controls i can simply add the call like this

Private _VC As New ValidateClass

Private Sub ComboBox1_Click(sender As Object, e As EventArgs) Handles ComboBox1.Click
   _VC.ValidateCombo(comboBox1)
End Sub

or

Private Sub ComboBox1_Click(sender As Object, e As EventArgs) Handles ComboBox1.Click
    TextBox1.Text = _VC.ValidateCombo(comboBox1)
End Sub

Answer 3

Hi @NachitoMax ,
You can take a look at the following code.

Public Class Validate  
  
    Public Sub New()  
    End Sub  
  
    Friend Function Validate(ByVal _control As Control) As String  
        If TypeOf _control Is TextBox Then  
            '...  
        ElseIf TypeOf _control Is Label Then  
            '...  
        ElseIf TypeOf _control Is ComboBox Then  
            Dim prop As PropertyInfo = _control.GetType.GetProperty("DropDownStyle")  
            Dim v As ComboBoxStyle = CType(prop.GetValue(_control), ComboBoxStyle)  
            prop.SetValue(_control, ComboBoxStyle.DropDownList)  
        End If  
        '...  
    End Function  
  
End Class  

It can help you get and set the value of the property dynamically according to the type of control at run time
Hope it could be helpful.

Best Regards,
Xingyu Zhao
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