Nullable(Of Type) and converting to value type

Category VB.Net Sub Category Manipulating Types

How to convert between these types in code.

In this example the RefNo property is held as a nullable type of integer.

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Public Property RefNo() As Nullable(Of Integer)
    Get
        If IsNothing(Session("RefNo")) Then
            Return Nothing
        Else
            Return CInt(Session("RefNo"))
        End If
    End Get
    Set(ByVal value As Nullable(Of Integer))
        Session("RefNo") = value
    End Set
End Property

To pass this RefNo property value into the ValidRefNo integer variable, use the following code snippet to perform this.

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Dim ValidRefNo as Integer

If RefNo.HasValue Then
    ValidRefNo = RefNo.Value
Else
    ValidRefNo = 0
End If

Other examples of using the nullable type in code:

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Dim i As Nullable(Of Integer)
Dim b As Boolean

i = Nothing
b = i.HasValue 'Will be False

i = 123
b = i.HasValue 'Will be True
Dim j As Integer = i.Value 'j = 123