本文整理汇总了VB.NET中System.NullReferenceException类的典型用法代码示例。如果您正苦于以下问题：VB.NET NullReferenceException类的具体用法？VB.NET NullReferenceException怎么用？VB.NET NullReferenceException使用的例子？那么恭喜您, 这里精选的类代码示例或许可以为您提供帮助。
在下文中一共展示了NullReferenceException类的11个代码示例，这些例子默认根据受欢迎程度排序。您可以为喜欢或者感觉有用的代码点赞，您的评价将有助于系统推荐出更棒的VB.NET代码示例。
示例1: Main
' 导入命名空间
Imports System.Collections.Generic
Module Example
Public Sub Main()
Dim names As List(Of String)
names.Add("Major Major Major")
End Sub
End Module
' Compilation displays a warning like the following:
' Example1.vb(10) : warning BC42104: Variable 'names' is used before it
' has been assigned a value. A null reference exception could result
' at runtime.
'
' names.Add("Major Major Major")
' ~~~~~输出：
Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object. at Example.Main()
示例2: Main
' 导入命名空间
Imports System.Collections.Generic
Module Example
Public Sub Main()
Dim names As New List(Of String)()
names.Add("Major Major Major")
End Sub
End Module示例3: Main
Module Example
Public Sub Main()
Dim values() As Integer
For ctr As Integer = 0 To 9
values(ctr) = ctr * 2
Next
For Each value In values
Console.WriteLine(value)
Next
End Sub
End Module输出：
Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object. at Example.Main()
示例4: Main
Module Example
Public Sub Main()
Dim values(9) As Integer
For ctr As Integer = 0 To 9
values(ctr) = ctr * 2
Next
For Each value In values
Console.WriteLine(value)
Next
End Sub
End Module输出：
0 2 4 6 8 10 12 14 16 18
示例5: Main
Module Example
Public Sub Main()
Dim persons() As Person = Person.AddRange( { "Abigail", "Abra",
"Abraham", "Adrian",
"Ariella", "Arnold",
"Aston", "Astor" } )
Dim nameToFind As String = "Robert"
Dim found As Person = Array.Find(persons, Function(p) p.FirstName = nameToFind)
Console.WriteLine(found.FirstName)
End Sub
End Module
Public Class Person
Public Shared Function AddRange(firstNames() As String) As Person()
Dim p(firstNames.Length - 1) As Person
For ctr As Integer = 0 To firstNames.Length - 1
p(ctr) = New Person(firstNames(ctr))
Next
Return p
End Function
Public Sub New(firstName As String)
Me.FirstName = firstName
End Sub
Public FirstName As String
End Class输出：
Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object. at Example.Main()
示例6: Main
Module Example
Public Sub Main()
Dim persons() As Person = Person.AddRange( { "Abigail", "Abra",
"Abraham", "Adrian",
"Ariella", "Arnold",
"Aston", "Astor" } )
Dim nameToFind As String = "Robert"
Dim found As Person = Array.Find(persons, Function(p) p.FirstName = nameToFind)
If found IsNot Nothing Then
Console.WriteLine(found.FirstName)
Else
Console.WriteLine("{0} not found.", nameToFind)
End If
End Sub
End Module
Public Class Person
Public Shared Function AddRange(firstNames() As String) As Person()
Dim p(firstNames.Length - 1) As Person
For ctr As Integer = 0 To firstNames.Length - 1
p(ctr) = New Person(firstNames(ctr))
Next
Return p
End Function
Public Sub New(firstName As String)
Me.FirstName = firstName
End Sub
Public FirstName As String
End Class输出：
Robert not found
示例7: Main
Module Example
Public Sub Main()
Dim pages As New Pages()
Dim title As String = pages.CurrentPage.Title
End Sub
End Module
Public Class Pages
Dim page(9) As Page
Dim ctr As Integer = 0
Public Property CurrentPage As Page
Get
Return page(ctr)
End Get
Set
' Move all the page objects down to accommodate the new one.
If ctr > page.GetUpperBound(0) Then
For ndx As Integer = 1 To page.GetUpperBound(0)
page(ndx - 1) = page(ndx)
Next
End If
page(ctr) = value
If ctr < page.GetUpperBound(0) Then ctr += 1
End Set
End Property
Public ReadOnly Property PreviousPage As Page
Get
If ctr = 0 Then
If page(0) Is Nothing Then
Return Nothing
Else
Return page(0)
End If
Else
ctr -= 1
Return page(ctr + 1)
End If
End Get
End Property
End Class
Public Class Page
Public URL As Uri
Public Title As String
End Class输出：
Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object. at Example.Main()
示例8: Main
Module Example
Public Sub Main()
Dim pages As New Pages()
Dim current As Page = pages.CurrentPage
If current IsNot Nothing Then
Dim title As String = current.Title
Console.WriteLine("Current title: '{0}'", title)
Else
Console.WriteLine("There is no page information in the cache.")
End If
End Sub
End Module输出：
There is no page information in the cache.
示例9: Main
Module Example
Public Sub Main()
Dim values() As String = { "one", Nothing, "two" }
For ctr As Integer = 0 To values.GetUpperBound(0)
Console.Write("{0}{1}", values(ctr).Trim(),
If(ctr = values.GetUpperBound(0), "", ", "))
Next
Console.WriteLine()
End Sub
End Module输出：
Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object. at Example.Main()
示例10: Main
Module Example
Public Sub Main()
Dim values() As String = { "one", Nothing, "two" }
For ctr As Integer = 0 To values.GetUpperBound(0)
Console.Write("{0}{1}",
If(values(ctr) IsNot Nothing, values(ctr).Trim(), ""),
If(ctr = values.GetUpperBound(0), "", ", "))
Next
Console.WriteLine()
End Sub
End Module输出：
one, , two
示例11: Main
' 导入命名空间
Imports System.Collections.Generic
Module Example
Public Sub Main()
Dim names As List(Of String) = GetData()
PopulateNames(names)
End Sub
Private Sub PopulateNames(names As List(Of String))
Dim arrNames() As String = { "Dakota", "Samuel", "Nikita",
"Koani", "Saya", "Yiska", "Yumaevsky" }
For Each arrName In arrNames
names.Add(arrName)
Next
End Sub
Private Function GetData() As List(Of String)
Return Nothing
End Function
End Module输出：
Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object. at Example.PopulateNames(List`1 names) at Example.Main()