Public Class Form1
    Enum operations
        none = 0
        add = 1
        substract = 2
        multiply = 3
        divide = 4
    End Enum

    Dim operation
    Dim n As Double
    Dim n2 As Double

    Private Sub calcul()
        If TextBox1.Text <> "" Then
            Select Case operation
                Case operations.add
                    n = n + Val(TextBox1.Text)
                Case operations.substract
                    n = n - Val(TextBox1.Text)
                Case operations.multiply
                    n = n * Val(TextBox1.Text)
                Case operations.divide
                    n = n / Val(TextBox1.Text)
                Case Else
                    n = Val(TextBox1.Text)
            End Select
        End If
        operation = operations.none
    End Sub
    Private Sub Button9_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button9.Click
        TextBox1.Text &= "9"
    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        operation = operations.none
        n = 0
        n2 = 0
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        TextBox1.Text &= "1"
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        TextBox1.Text &= "2"
    End Sub

    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        TextBox1.Text &= "3"
    End Sub

    Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click
        TextBox1.Text &= "4"
    End Sub

    Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button5.Click
        TextBox1.Text &= "5"
    End Sub

    Private Sub Button6_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button6.Click
        TextBox1.Text &= "6"
    End Sub

    Private Sub Button7_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button7.Click
        TextBox1.Text &= "7"
    End Sub

    Private Sub Button8_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button8.Click
        TextBox1.Text &= "8"
    End Sub

    Private Sub Button10_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button10.Click
        TextBox1.Text &= "0"
    End Sub

    Private Sub Button11_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button11.Click
        'Butonul C
        n = 0
        TextBox1.Text = ""
        operation = operations.none
    End Sub

    Private Sub Button12_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button12.Click
        'Butonul =
        calcul()
        TextBox1.Text = n
    End Sub

    Private Sub Button13_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button13.Click
        'Butonul +
        calcul()
        TextBox1.Text = ""
        operation = operations.add
    End Sub

    Private Sub Button14_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button14.Click
        'Butonul -
        calcul()
        TextBox1.Text = ""
        operation = operations.substract
    End Sub

    Private Sub Button15_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button15.Click
        'Butonul *
        calcul()
        TextBox1.Text = ""
        operation = operations.multiply
    End Sub

    Private Sub Button16_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button16.Click
        'Butonul /
        calcul()
        TextBox1.Text = ""
        operation = operations.divide
    End Sub

    Private Sub Button17_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button17.Click
        'Butonul .
        If TextBox1.Text <> "" And Not TextBox1.Text.Contains(".") Then
            TextBox1.Text &= "."
        End If
        Dim Имя As String

        Имя = "Билл"
Если Имя = "Билл" Then MsgBox ("Имя Билл")
    End Sub

    Private Sub Button18_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button18.Click
        'Butonul +/-
        TextBox1.Text = -Val(TextBox1.Text)
    End Sub

    Private Sub Form1_KeyDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles MyBase.KeyDown

    End Sub

    Private Sub Form1_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles MyBase.KeyPress

    End Sub

    Private Sub Form1_MouseDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles MyBase.MouseDown

    End Sub

    Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged

    End Sub
End Class