How to get ALL child controls of a WinForm of a specific type (Button/Textbox)?

Question

I need to get all controls on a form that are of type x, I'm pretty sure I saw that code once in the past that used something like this:

dim ctrls() as Control
ctrls = Me.Controls(GetType(TextBox))

I know I can iterate over all controls getting children using a recursive function, but wondering if there is something more easier or straightforward, maybe:

Dim Ctrls = From ctrl In Me.Controls Where ctrl.GetType Is Textbox

Kind regards

Answer 1

In C# (since you tagged it as such) you could use a LINQ expression like this:

List<Control> c = Controls.OfType<TextBox>().Cast<Control>().ToList();

---

Edit for recursion:

In this example, you first create the list of controls and then call a method to populate it. Since the method is recursive, it doesn't return the list, it just updates it.

List<Control> ControlList = new List<Control>();
private void GetAllControls(Control container)
{
    foreach (Control c in container.Controls)
    {
        GetAllControls(c);
        if (c is TextBox) ControlList.Add(c);
    }
}

It may be possible to do this in one LINQ statement using the Descendants function, though I am not as familiar with it. See this page for more information on that.

Answer 2

You can use a LINQ query to do this. This will query everything on the form that is type TextBox

var c = from controls in this.Controls.OfType<TextBox>()
              select controls;

Answer 3

Maybe this one ?

Public Function getControls(Of T)() As List(Of T)
    Dim st As New Stack(Of Control)
    Dim ctl As Control
    Dim li As New List(Of T)

    st.Push(Me)

    While st.Count > 0
        ctl = st.Pop
        For Each c In ctl.Controls
            st.Push(CType(c, Control))
            If c.GetType Is GetType(T) Then
                li.Add(CType(c, T))
            End If
        Next
    End While

    Return li
End Function

I think the function to get all controls you are talking about is only available to WPF.

Cheers !

Answer 4

Here's another option for you. I tested it by creating a sample application, I then put a GroupBox and a GroupBox inside the initial GroupBox. Inside the nested GroupBox I put 3 TextBox controls and a button. This is the code I used (even includes the recursion you were looking for)

public IEnumerable<Control> GetAll(Control control,Type type)
{
    var controls = control.Controls.Cast<Control>();

    return controls.SelectMany(ctrl => GetAll(ctrl,type)).Concat(controls).Where(c => c.GetType() == type);
}

To test it in the form load event I wanted a count of all controls inside the initial GroupBox

private void Form1_Load(object sender, EventArgs e)
{
    var c = GetAll(this,typeof(TextBox));
    MessageBox.Show("Total Controls: " + c.Count());
}

And it returned the proper count each time, so I think this will work perfectly for what you're looking for :)