VBasic Calculator

Public Class Form1
    Private Sub TextBox1_TextChanged(sender As Object, e As EventArgs) Handles txtbox1.TextChanged

    End Sub

    Private Sub btn1_Click(sender As Object, e As EventArgs) Handles btn1.Click
        txtbox1.Text = txtbox1.Text + "1"
    End Sub

    Private Sub btn2_Click(sender As Object, e As EventArgs) Handles btn2.Click
        txtbox1.Text = txtbox1.Text + "2"
    End Sub

    Private Sub btn3_Click(sender As Object, e As EventArgs) Handles btn3.Click
        txtbox1.Text = txtbox1.Text + "3"
    End Sub

    Private Sub btn4_Click(sender As Object, e As EventArgs) Handles btn4.Click
        txtbox1.Text = txtbox1.Text + "4"
    End Sub

    Private Sub btn5_Click(sender As Object, e As EventArgs) Handles btn5.Click
        txtbox1.Text = txtbox1.Text + "5"
    End Sub

    Private Sub btn6_Click(sender As Object, e As EventArgs) Handles btn6.Click
        txtbox1.Text = txtbox1.Text + "6"
    End Sub

    Private Sub btn7_Click(sender As Object, e As EventArgs) Handles btn7.Click
        txtbox1.Text = txtbox1.Text + "7"
    End Sub

    Private Sub btn8_Click(sender As Object, e As EventArgs) Handles btn8.Click
        txtbox1.Text = txtbox1.Text + "8"
    End Sub

    Private Sub btn9_Click(sender As Object, e As EventArgs) Handles btn9.Click
        txtbox1.Text = txtbox1.Text + "9"
    End Sub

    Private Sub btn0_Click(sender As Object, e As EventArgs) Handles btn0.Click
        txtbox1.Text = txtbox1.Text + "0"
    End Sub
    Dim num1, num2 As Integer
    Dim oper As String
    Private Sub btnadd_Click(sender As Object, e As EventArgs) Handles btnadd.Click
        num1 = txtbox1.Text
        oper = "+"
        txtbox1.Clear()
    End Sub

    Private Sub btnsub_Click(sender As Object, e As EventArgs) Handles btnsub.Click
        num1 = txtbox1.Text
        oper = "-"
        txtbox1.Clear()
    End Sub

    Private Sub btneq_Click(sender As Object, e As EventArgs) Handles btneq.Click
        num2 = txtbox1.Text
        txtbox1.Clear()
        If oper = "+" Then
            txtbox1.Text = num1 + num2
        ElseIf oper = "-" Then
            txtbox1.Text = num1 - num2
        End If
    End Sub
End Class