我得到一个错误“不设置到对象的实例对象引用”

Question

这背后

Private Property ListEmployee As List(Of Employee) 
    Get 
     Return Session(Me.GetType.Name) 
    End Get 
    Set(ByVal value As List(Of Employee)) 
     Session(Me.GetType.Name) = value 
    End Set 
End Property 
Private ReadOnly Property objEmployee As Employee 
    Get 
     Dim obj As New Employee 
     obj.User_ID = txtUserID.Text.Trim 
     obj.Name = txtName.Text.Trim 
     obj.Position = txtPosition.Text.Trim 
     Return obj 
    End Get 
End Property 
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load 

End Sub 
Protected Sub btnAddtoTable_Click(sender As Object, e As EventArgs) Handles btnAddtoTable.Click 
    ListEmployee.Add(objEmployee) 'error at here 
    gvResult.DataSource = ListEmployee 
    gvResult.DataBind() 
End Sub 

末级

我尝试数据（类员工）加入到ListEmployee为我的代码（员工列表），然后显示在gridview上，但我得到一个错误。

Answer 1

这是最好的断点和拆分功能，看看错误的地方，但看你的代码我很确定问题是在ListEmployee对象。 ListEmployee.Add()将获得对ListEmplyee对象的引用，并且您不检查该对象是否实际存在。你需要做一些数据验证在两个ListEmployee属性和objEmployee检查，我会做它在ListEmployee你在这里：

Private Property ListEmployee As List(Of Employee) 
Get 
    If Not IsNothing(Session(Me.GetType.Name)) Then 
     Return Session(Me.GetType.Name) 
    Else 
     Dim le as New List(Of Employee) 
     le.add(objEmployee) 
     Session(Me.GetType.Name) = le 
     Return le 
    End If 
End Get 
Set(ByVal value As List(Of Employee)) 
    Session(Me.GetType.Name) = value 
End Set 
End Property