programa que calcula el factorial de un numero hecho por monica gabriela segundo gonzalez

Public Class Form1

   

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

 Dim a As Integer

a = Val(TextBox1.Text) Mod 2
 If TextBox1.Text <> "" Then

  If a <> 0 Then

 Label1.Text = "Es numero impar"

  Else

  Label1.Text = "Es numero par"

   End If

    Else

 MsgBox("No a introducido datos,favor de intentar de nuevo", vbYes + vbCritical, "error")

 End If

 End Sub

 Private Sub textbox1_textchanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged

 Button1.Enabled = True

 End Sub

End Class