大家帮我看下这个图片储存的问题吧！

总是说image_url1不接受空值，我把非空属性改了之后错误时没了，但是数据表top_list_left里的image_url里
根本没有东西啊，fileupload更本就没有上传成功，麻烦各位大大帮我解答下市为什么，谢谢 protected void LinqDataSource1_Inserting(object sender, LinqDataSourceInsertEventArgs e)
    {
        Top_list_left uploadpic1 = (Top_list_left)e.NewObject;
       // uploadpic1.Class_1 = Convert.ToString(Request.QueryString.Get("Class_1"));
        FileUpload FileUpload1 = (FileUpload)ListView1.InsertItem.FindControl("FileUpload1");
        string virtualFolder = "~/BigPics/";
        string physicalFolder = Server.MapPath(virtualFolder);
        string fileName = Guid.NewGuid().ToString();
        string extension = System.IO.Path.GetExtension(FileUpload1.FileName);
        FileUpload1.SaveAs(System.IO.Path.Combine(physicalFolder,fileName+extension));
        uploadpic1.ImageUrl_1 = virtualFolder+fileName+extension;
    }
    protected void ListView1_ItemInserting(object sender, ListViewInsertEventArgs e)
    {
        FileUpload FileUpload1 = (FileUpload)ListView1.InsertItem.FindControl("FileUpload1");
        if (!FileUpload1.HasFile || !FileUpload1.FileName.ToLower().EndsWith(".jpg"))
        {
            CustomValidator CustomValidator1 = (CustomValidator)ListView1.InsertItem.FindControl("CustomValidator1");
            CustomValidator1.IsValid = false;
            e.Cancel = true;
        }
    }