c# – 分配Session变量/值时出现NullReferenceException

public uint MyPropery 
{
    get 
    {
        object o = Session["MyProperty"];
        if (o != null)
            return (uint)o;
        else
            return 0;
    }
    set 
    {
        Session["MyProperty"] = value;
    }
}

但是,这次我在setter中得到了NullReferenceException.据我所知,以上述方式分配Session变量是有效的.此外,Session不为null,也不是值.

有什么想法吗？

编辑：

添加属性所在的UserControl的代码.我正在使用ext.net,但这不应该与此有任何关系.我想到了一个想法：

UserControl(如下所示)是在页面的代码隐藏中动态添加的.这与它有什么关系吗？

我正在添加像这样的UserControls(在页面上)：

foreach(CoreCommons.System.Comment c in cg.Reply_Comments)
{
    WebApplicationExtNetTest.Secure.UserControls.CoreComment cc = new UserControls.CoreComment();
    cc._Comment = c; // here is where i get the NullRef
    this.Panel1.ContentControls.Add(cc);
}

标记：

<%@ Control Language="C#" AutoEventWireup="true" CodeBehind="CoreComment.ascx.cs" Inherits="WebApplicationExtNetTest.Secure.UserControls.CoreComment" %>
<%@ Register Assembly="Ext.Net" Namespace="Ext.Net" TagPrefix="ext" %>

<ext:Panel runat="server" ID="CoreCommentOuterPanel" BodyStyle="background: #FFFDDE">
    <Items>
        <ext:ColumnLayout runat="server">
            <Columns>
                <ext:LayoutColumn ColumnWidth="0.8">
                    <ext:Image runat="server" ImageUrl="/Resources/bullet_triangle_green_16x16.png" Align="AbsMiddle"></ext:Image> 
                    <ext:Label runat="server" ID="lblCommentInfo"></ext:Label>
                </ext:LayoutColumn>
                <ext:LayoutColumn ColumnWidth="0.2"><ext:Button runat="server" ID="btnDelete" Icon="Delete"></ext:Button></ext:LayoutColumn>
            </Columns>
        </ext:ColumnLayout>
        <ext:Label runat="server" ID="lblComment"></ext:Label>
    </Items>
</ext:Panel>

代码隐藏：

namespace WebApplicationExtNetTest.Secure.UserControls
{
    public partial class CoreComment : System.Web.UI.UserControl
    {
        public CoreCommons.System.Comment _Comment
        {
            get
            {
                object o = Session["CoreComment_ObjectId"];
                if (o != null)
                    return (tWorks.Core.CoreCommons.System.Comment)o;
                else
                    return null;
            }
            set
            {
                Session["CoreComment_ObjectId"] = value;
                SetComment();
            }
        }            

        protected void Page_Load(object sender,EventArgs e)
        {    
        }

        private void SetComment()
        {
            if (_Comment == null)
            {
                lblCommentInfo.Text = "";
                lblComment.Text = "";
            }
            else
            {
                lblCommentInfo.Text = _Comment.Author + "," + _Comment.TimeStamp.ToString("g");
                lblComment.Text = _Comment.Text;
            }
        }
    }
}