未将对象引用设置到对象的实例

[wawa510512122]

源错误:


行 30: {
行 31:
行 32: string sstr1 = Session["drop1"].ToString();
行 33: string sstr2 = Session["drop2"].ToString();
行 34: string sstr3 = Session["drop3"].ToString();

堆栈跟踪:


[NullReferenceException: 未将对象引用设置到对象的实例。]
HouAdmin_InsertShiTi.btnAdd_Click(Object sender, EventArgs e) in d:\My Documents\Visual Studio 2005\WebSites\WebSite3\HouAdmin\InsertShiTi.aspx.cs:32
System.Web.UI.WebControls.Button.OnClick(EventArgs e) +75
System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +97
System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +7
System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +11
System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +33
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +4919


protected void btnAdd_Click(object sender, EventArgs e)
{

string sstr1 = Session["drop1"].ToString();
string sstr2 = Session["drop2"].ToString();
string sstr3 = Session["drop3"].ToString();
if (ddlType.SelectedIndex == 0)
{
dataconn.eccom("insert into tb_Questions"
+ "(que_lessonid,que_subject,que_type,optionA,optionB,optionC,optionD,option0,option1,que_answer)"
+"values('" + sstr1 + "','" + sstr2 + "','" + sstr3 + "','" + this.txtExamTitle.Text
+ "','" + ddlType.Text + "','" + this.txtExamA.Text + "','" + this.txtExamB.Text
+ "','" + this.txtExamC.Text + "','" + this.txtExamD.Text + "','"
+ ddlAnswer.Text + "')");
Response.Redirect("kaoshi_timu.aspx");
}
else
{

if (cblAnswer.Items[0].Selected == true && cblAnswer.Items[1].Selected == false && cblAnswer.Items[2].Selected == false && cblAnswer.Items[3].Selected == false)
{
string str1 = "A";
dataconn.eccom("insert into tb_Questions"
+ "(que_lessonid,que_subject,que_type,optionA,optionB,optionC,optionD,que_answer)"
+"values('" + sstr1 + "','" + sstr2 + "','" + sstr3 + "','" + this.txtExamTitle.Text
+ "','" + ddlType.Text + "','" + this.txtExamA.Text + "','" + this.txtExamB.Text
+ "','" + this.txtExamC.Text + "','" + this.txtExamD.Text + "','" + str1
+ "')");

他们说我没赋值，请问我应该怎么赋值啊。。。最好告诉我具体的，我是新手

[wuyq11]

string sstr1 = Session["drop1"]?==null?"":Session["drop1"].ToString();
string sstr2 = Session["drop2"]?==null?"":Session["drop2"].ToString();
string sstr3 = Session["drop3"]?==null?"":Session["drop3"].ToString();

[wuyq11]

string sstr1 = Session["drop1"]==null?"":Session["drop1"].ToString();

[llsen]

行 32: string sstr1 = Session["drop1"].ToString();
行 33: string sstr2 = Session["drop2"].ToString();
行 34: string sstr3 = Session["drop3"].ToString();

没有给session赋值，然后取值，就出错了
拿一个举例子

string sstr1 = null;
if(Session["drop1"]!=null)
{
   sstr1 = Session["drop1"].ToString(); 
}

[蔡袅]

string sstr1 = Session["drop1"].ToString();
string sstr2 = Session["drop2"].ToString();
string sstr3 = Session["drop3"].ToString();

楼主看看这个有没有赋值过，Session["drop"]=XXX;
最好是前面加个
if(Session["drop"]!=null)
{
//你的代码
}

[Sysping1]

[Quote=引用 2 楼 xx_mm 的回复:]
string sstr1 = Session["drop1"].ToString();
string sstr2 = Session["drop2"].ToString();
string sstr3 = Session["drop3"].ToString();

楼主看看这个有没有赋值过，Session["drop"]=XXX;
最好是前面加个
if(Session["drop"]!=null)
{
//你的代码
}
[/Quote]
UP

[wawa510512122]

编译器错误信息: CS0128: 已在此范围定义了名为“sstr1”的局部变量。

源错误:



行 45: sstr3 = Session["drop3"].ToString();
行 46: }
行 47: string sstr1 = Session["drop1"].ToString();
行 48: string sstr2 = Session["drop2"].ToString();
行 49: string sstr3 = Session["drop3"].ToString();

[该昵称已被占用_]

session应该是没值,你赋值

调试一下就清楚了

[烈火蜓蜻]

[Quote=引用 2 楼 xx_mm 的回复:]
string sstr1 = Session["drop1"].ToString();
string sstr2 = Session["drop2"].ToString();
string sstr3 = Session["drop3"].ToString();

楼主看看这个有没有赋值过，Session["drop"]=XXX;
最好是前面加个
if(Session["drop"]!=null)
{
//你的代码
}
[/Quote]

对