未将对象引用设置到对象的实例

Question

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using NS_DBOP;

public partial class Flow_ArchivesInfo : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            Bind();
        }
    }
    public string path = null;
    public string id = null;
    public void Bind()
    {
        id = Request.QueryString["id"].ToString();
        DataSet ds = new DBoperate().ExecuteQuery("select * from FlowDoc where ID=" + Convert.ToInt32(Request.QueryString["id"]),0,0,"flowdoc");
        foreach(DataRow dr in ds.Tables[0].Rows)
        {
            this.lblTitle.Text = dr["Title"].ToString();
            this.lblStep.Text = new DBoperate().ExecuteScalar("select Name from Flow where ID=" + Convert.ToInt32(dr["FlowID"])).ToString();
            this.lblUrgent.Text =dr["IsUrgent"].ToString().Equals("0") ?  "一般" :"重要";
            this.lblUser.Text = new DBoperate().ExecuteScalar("select Name from Employee where Employeeid=" + dr["UserID"]).ToString();
            this.lblPubDate.Text = dr["PubDate"].ToString();
            this.txtcontent.Value = dr["Content"].ToString();
            path = dr["Attachment"].ToString();
            string[] a;
            a = path.Split(';');
            string[] AccIDList ={ "0" };
            for (int i = 0; i < a.Length; i++)
            {

                //LblAcc.Text += "<a href=\"upfiles/" + "+a[i]+"+  target=\"_blank\">" + a[i] + "</a>" + "&nbsp" + "&nbsp";
                this.lblAr.Text += "<a href=\"Files/"
                        + a[i]
                        + "\" target=\"_blank\">"
                        + a[i]
                        + "</a>" + "&nbsp" + "&nbsp";
            }
        }

        string sql = "select * from FlowAction where ID in (select ActionID from FlowStep where FlowID in (select FlowID from FlowDoc where ID=" + Convert.ToInt32(Request.QueryString["id"]) + "))";
        DataSet dsstep = new DBoperate().ExecuteQuery(sql, 0, 0, "flowstep");
        string step = null;
        foreach (DataRow drs in dsstep.Tables[0].Rows)
        {
            step += Convert.ToString(drs["Name"]) + "-->";
        }
        this.lblStep.Text = step + "完成";
    }
}

错误提示： id = Request.QueryString["id"].ToString();——>未将对象引用设置到对象的实例.
请问：这该怎样修改？

Answer 1

添加一个判断

if(Request.QueryString["id"]!=null)

{

  id = Request.QueryString["id"].ToString();

}

---

努力+方法=成功

Answer 2

你好 请你检查你的URL中是否有如http://www.xxx.com/xxx.aspx?id=2222中的id

你可以通過下麵的代碼判斷

if(Request.QueryString["id"]!=null)

id=Request.QueryString["id"].ToString();

else

throw new Exception("id 為空！");

---

I see you~http://hi.baidu.com/1987raymondMy Blog~~~

Answer 3

Request.QueryString[“id"] 返回类型已经是 string，请不要对它再调用 ToString 方法，这是纯粹是画蛇添足，还带来了问题潜在的空引用问题

id = Request.QueryString[“id"]; // 可能 null，因为url 中没有查询参数 id

if(id != null) {

// your codes .....

}

---

问题要简单，错误须详细@错误/异常/堆栈信息+操作系统+软件版本+all the context of the issue Hope Helpful | http://www.leoworks.net

Answer 4

您可以尝试如下方法：

if(!string.IsNullOrEmpty(Request.QueryString["id"]))

{

  id = Request.QueryString["id"].ToString();

}

else

{

   id = 设置一个默认值;

}

然后使用id操作