Question

Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) _
    Handles Button1.Click  
    EmptyTextBoxValues(Me)  
End Sub  

Private Sub EmptyTextBoxValues(ByVal parent As Control)  
    For Each c As Control In parent.Controls  
        If (c.Controls.Count > 0) Then  
            EmptyTextBoxValues(c)  
        Else  
            If TypeOf c Is TextBox Then  
                CType(c, TextBox).Text = ""  
            End If  
        End If  
    Next  
End Sub  

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This sub is for to clear all textboxes value, i just need to know how did it work ??

Answer 1

The EmptyTextBoxValues sub recursively calls all child controls (if they exists) – if non exist, it checks if they are a text box and if so, clears it.

To start – it loops through every child control belonging to the passed in control:

For Each c As Control In parent.Controls

It then tests whether the child control has any child controls of its own, and if so, calls itself with the child control:

    If (c.Controls.Count > 0) Then  
        EmptyTextBoxValues(c)  

If no such child controls exist on the child control, a test is made whether the type of the control is of TextBox and if so, it is cleared:

    Else  
        If TypeOf c Is TextBox Then  
            CType(c, TextBox).Text = ""  
        End If