Вывод информации в Label в зависимости от того, что введено в TextBox

Public Class Form1
    Dim tgx, ctgx, cosx, sinx As String
 
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
 
        tgx = "sinx / cosx"
        ctgx = "cosx / sinx"
        Label1.Text = tgx
        Label1.Text = ctgx
    End Sub
 
End Class

Public Class Form1
 
 
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
 
 
if textbox1.text ="tgx" then 
    Label1.Text ="sinx / cosx"
elseif textbox1.text ="ctgx" then
    Label1.Text =  "cosx / sinx"
else
    Label1.Text = ""
end if
 
 
End Sub
 
End Class

Sub Button1Click(sender As Object, e As EventArgs)      
Const N = 2
Dim expar(N,2), str As String
Dim i,index As Integer
 
str = "Нет совпадений"
expar(0,0) = "tg x"
expar(0,1) = "sin x / cos x"
 
expar(1,0) = "ctg x"
expar(1,1) = "cos x / sin x"
 
For i = 0 To N
    If textBox1.Text = expar(i,0) Then
        str = expar(i,1)
    End If
Next
label1.Text = str
    End Sub