Failed to create object of type "System.Windows.Forms.Button" for input> "System.Windows.Forms.TextBox"

Question

I wrote a function that empties all TextBox in my form:

Private Sub effacer() For Each t As TextBox In Me.Controls t.Text = Nothing Next End Sub 

But I had this problem:

Cannot pass an object of type 'System.Windows.Forms.Button' to input of type 'System.Windows.Forms.TextBox'.

I tried adding this If TypeOf t Is TextBox Then , but I had the same problem

Answer 1

Controls contains all formBoxes controls.

Instead, you can use Enumerable.OfType to find and discard all TextBoxes :

 For Each txt As TextBox In Me.Controls.OfType(Of TextBox)() txt.Text = "" Next 

If you want to do the same in the old school style:

 For Each ctrl As Object In Me.Controls If TypeOf ctrl Is TextBox DirectCast(ctrl, TextBox).Text = "" End If Next 

Answer 2

 For Each t As TextBox In Me.Controls 

This line right here is trying to pass a TextBox to each control.
You need to change this to As Control or use Me.Controls.OfType(Of TextBox)() to filter the collection before iterating.

Answer 3

Here is a line of code that will clear all radioButtons from a groupBox that is attached to button_click:

 groupBoxName.Controls.OfType<RadioButton>().ToList().ForEach(p => p.Checked = false); 

Use the appropriate changes to adapt them to your needs.