VB.Net/Language Basics/nullable
Check if nullable is null
<source lang="vbnet">
Option Explicit On Option Strict On Class MyClass1
Public numericValue As Integer? Public boolValue As Boolean? = True Public Function GetIntFromDatabase() As Integer? Return numericValue End Function Public Function GetBoolFromDatabase() As Boolean? Return boolValue End Function
End Class Module Program
Sub Main() Dim dr As New MyClass1() Dim i As Integer? = dr.GetIntFromDatabase() If (i.HasValue) Then Console.WriteLine("Value of "i" is: {0}", i.Value) Else Console.WriteLine("Value of "i" is undefined.") End If Dim b As Boolean? = dr.GetBoolFromDatabase() If (b.HasValue) Then Console.WriteLine("Value of "b" is: {0}", b.Value) Else Console.WriteLine("Value of "b" is undefined.") End If End Sub
End Module
</source>
Main with Nullable (Of T)
<source lang="vbnet"> Class MyClass1
Public numericValue As Nullable(Of Integer) Public boolValue As Nullable(Of Boolean) = True Public Function GetIntFromDatabase() As Nullable(Of Integer) Return numericValue End Function Public Function GetBoolFromDatabase() As Nullable(Of Boolean) Return boolValue End Function Public Shared Sub Main() Dim dr As New MyClass1() Dim i As Nullable(Of Integer) = dr.GetIntFromDatabase() If (i.HasValue) Then Console.WriteLine("Value of "i" is: {0}", i.Value) Else Console.WriteLine("Value of "i" is undefined.") End If Dim b As Nullable(Of Boolean) = dr.GetBoolFromDatabase() If (b.HasValue) Then Console.WriteLine("Value of "b" is: {0}", b.Value) Else Console.WriteLine("Value of "b" is undefined.") End If End Sub
End Class
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