Generiklar va Nothing xavfsizligi

Module Dastur
    Function Almashtir(Of T)(ByRef a As T, ByRef b As T)
        Dim vaqtinchalik As T = a
        a = b
        b = vaqtinchalik
    End Function

    Sub Main()
        Dim x As Integer = 10, y As Integer = 20
        Almashtir(x, y)
        Console.WriteLine($"{x}, {y}")

        Dim m As String = "birinchi", n As String = "ikkinchi"
        Almashtir(m, n)
        Console.WriteLine($"{m}, {n}")
    End Sub
End Module

Public Class Quti(Of T)
    Private _elementlar As New List(Of T)

    Public Sub Solish(element As T)
        _elementlar.Add(element)
    End Sub

    Public Function Olish(indeks As Integer) As T
        Return _elementlar(indeks)
    End Function

    Public ReadOnly Property Soni As Integer
        Get
            Return _elementlar.Count
        End Get
    End Property
End Class

Module Dastur
    Sub Main()
        Dim sonlar As New Quti(Of Integer)
        sonlar.Solish(10)
        sonlar.Solish(20)
        Console.WriteLine($"{sonlar.Soni} ta, birinchisi {sonlar.Olish(0)}")

        Dim ismlar As New Quti(Of String)
        ismlar.Solish("Malika")
        Console.WriteLine($"{ismlar.Soni} ta, birinchisi {ismlar.Olish(0)}")
    End Sub
End Module

Module Dastur
    Function Kattasi(Of T As IComparable(Of T))(a As T, b As T) As T
        If a.CompareTo(b) >= 0 Then
            Return a
        End If
        Return b
    End Function

    Sub Main()
        Console.WriteLine(Kattasi(15, 42))
        Console.WriteLine(Kattasi("olma", "anor"))
        Console.WriteLine(Kattasi(3.7, 2.1))
    End Sub
End Module

Public Class Omborxona(Of T As {Class, New})
    Public Function Yangi() As T
        Return New T()
    End Function
End Class

Public Class Hujjat
    Public Property Nom As String = "yangi hujjat"
End Class

Module Dastur
    Sub Main()
        Dim o As New Omborxona(Of Hujjat)
        Dim h As Hujjat = o.Yangi()
        Console.WriteLine(h.Nom)
    End Sub
End Module

Module Dastur
    Function Topish(royxat As List(Of String), qidiruv As String) As String
        For Each s As String In royxat
            If s = qidiruv Then
                Return s
            End If
        Next
        Return Nothing
    End Function

    Sub Main()
        Dim royxat As New List(Of String) From {"olma", "anor"}

        Dim topildi As String = Topish(royxat, "uzum")
        Console.WriteLine(topildi Is Nothing)

        If topildi IsNot Nothing Then
            Console.WriteLine(topildi.ToUpper())
        Else
            Console.WriteLine("Topilmadi")
        End If
    End Sub
End Module

Module Dastur
    Sub Main()
        Dim ball As Integer? = Nothing
        Console.WriteLine(ball.HasValue)
        Console.WriteLine(ball.GetValueOrDefault())
        Console.WriteLine(ball.GetValueOrDefault(-1))

        ball = 88
        Console.WriteLine(ball.HasValue)
        Console.WriteLine(ball.Value)
    End Sub
End Module

Module Dastur
    Sub Korsat(nom As String, ball As Integer?)
        If ball.HasValue Then
            Console.WriteLine($"{nom}: {ball.Value} ball")
        Else
            Console.WriteLine($"{nom}: imtihon topshirmagan")
        End If
    End Sub

    Sub Main()
        Korsat("Malika", 88)
        Korsat("Husanboy", 0)
        Korsat("Nodira", Nothing)
    End Sub
End Module

Module Dastur
    Sub Main()
        Dim kiritilgan As String = Nothing
        Console.WriteLine(If(kiritilgan, "noma'lum"))

        Dim ball As Integer? = Nothing
        Console.WriteLine(If(ball, 0))

        Dim royxat As List(Of String) = Nothing
        Dim xavfsiz = If(royxat, New List(Of String))
        Console.WriteLine(xavfsiz.Count)
    End Sub
End Module

Module Dastur
    Function XavfsizOrtacha(sonlar As List(Of Integer)) As Double?
        If sonlar Is Nothing OrElse sonlar.Count = 0 Then
            Return Nothing
        End If
        Return sonlar.Average()
    End Function

    Sub Main()
        Dim toliq As New List(Of Integer) From {80, 90, 100}
        Dim bosh As New List(Of Integer)

        Dim a As Double? = XavfsizOrtacha(toliq)
        Dim b As Double? = XavfsizOrtacha(bosh)

        Console.WriteLine(If(a.HasValue, a.Value.ToString(),
                             "hisoblab bo'lmadi"))
        Console.WriteLine(If(b.HasValue, b.Value.ToString(),
                             "hisoblab bo'lmadi"))
    End Sub
End Module