[عيد مبارك]

كود :

Public Class Form1

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Array.ForEach(FindControls(Me, "TextBox1").OfType(Of TextBox). _
                      ToArray, Sub(txt As TextBox) txt.Text = "123")
    End Sub


    Private Function FindControls(c As Control, n As String) As IEnumerable(Of Control)
        Dim cs = c.Controls.Cast(Of Control)()
        Return cs.SelectMany(Function(ctrl) FindControls(ctrl, n)). _
               Concat(cs).Where(Function(x) x.Name.Equals(n))
    End Function

End Class