对象引用设置为object的实例 [英] Object reference is set to instance of object

问题描述

protected void listPOItems_OnItemEditing(object sender, System.Web.UI.WebControls.ListViewEditEventArgs e)
 {
     listPOItems.EditIndex = e.NewEditIndex;
     qcpackingitemscollections objItems = new qcpackingitemscollections();
     if (Session["StoresIndentItemCollection"] != null)
         objItems = (qcpackingitemscollections)Session["StoresIndentItemCollection"];

     listPOItems.DataSource = objItems;
     listPOItems.DataBind();
   //  BindEditDDLs();
   //  DropDownList ddlMate = (DropDownList)listIndentItems.Items[e.NewEditIndex].FindControl("ddlMaterials");
     TextBox txtseno = (TextBox)listPOItems.Items[e.NewEditIndex].FindControl("txtseno");
     List<PackingInstructionItem> objIndentItemCollection = new List<PackingInstructionItem>();
     if (Session["StoresIndentItems"] != null)
         objIndentItemCollection = (List<PackingInstructionItem>)Session["StoresIndentItems"];

     var selVal = objIndentItemCollection.Where(i => i.ItemId == e.NewEditIndex + 1).Single();
// The below line Object reference is set to instance of object error will occured//
     txtseno.Text =Convert.ToString( selVal.SerialNo);

    ScriptManager.GetCurrent(this).SetFocus(txtseno);
 }

推荐答案

当您尝试访问对象的属性为null时，会发生此错误。



尝试调试并逐步查看源代码。

它肯定会帮助您找出错误发生的位置，然后您可以根据需要应用修复程序。



最有可能的原因是您尝试访问的Session对象，例如 Session [StoresIndentItemCollection] null 。

This error occurs when you try and access an attribute of an object that is null.

Try debugging and step though your source code.
It will surely help you find out where the error occurs and then you can apply a fix as appropriate.

Most likely cause is that the Session objects that you are trying to access e.g. Session["StoresIndentItemCollection"] are null.

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