Public Class frmChapa
    Private Sub btCalcular_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btCalcular.Click
        
        Dim texto As String

        
        Dim x As Integer
        Dim y As Integer

        
        Dim caracter As Char

        
        Dim CaracterRepetido As Integer

       
        texto = Me.txtCalcular.Text

       
        If Me.txtCalcular.Text.Length = 0 Then
            MessageBox.Show("Ingrese la cadena de caracteres", "Calcular", MessageBoxButtons.OK, MessageBoxIcon.Warning)
        Else
           CaracterRepetido = 0
            For x = 0 To texto.Length - 1
                caracter = texto.Chars(x)
                For y = 0 To texto.Length - 1
                    If y <> x Then
                        If caracter = texto.Chars(y) Then
                            CaracterRepetido = CaracterRepetido + 1
                        End If
                    End If
                Next
            Next
            
            If CaracterRepetido <> 0 Then
                MessageBox.Show("Se encontraron caracteres repetidos", "Control de caracteres", MessageBoxButtons.OK, MessageBoxIcon.Information)
            Else
                MessageBox.Show("No se encontraron caracteres repetidos", "Control de caracteres", MessageBoxButtons.OK, MessageBoxIcon.Information)
            End If
        End If
        CaracterRepetido = 0
    End Sub
End Class