asp.net Gridview using querrystring

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Hello programmers, got a few question here. Im getting an error saying Object reference not set to an instance of an object. on this part Label1.Text = Request.QueryString("CourseCatID").ToString But I think my syntax is correct. Any Ideas?

XML

<asp:TemplateField HeaderText="Edit">
    <ItemTemplate>
         <asp:LinkButton ID="LinkButton1" runat="server" PostBackUrl='<%#"CourseList.aspx?ID=" & Eval("CourseCatID")%>'  Text="Edit Courses"></asp:LinkButton>
   </ItemTemplate>
</asp:TemplateField>

Updated:
I think my requestquerystring is not null since ive got this on address bar
http://localhost:4543/Trainingplan/CourseList.aspx?ID=6

Posted 4-Oct-11 22:15pm

janwel

Updated 4-Oct-11 22:25pm

v2

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3 solutions

Solution 3

C#

<asp:linkbutton id="lnkEdit" postbackurl="<%# "CourseList.aspx?ID=" + Eval("ID")%>" text="Edit Courses" runat="server" xmlns:asp="#unknown"></asp:linkbutton>

and in redirected page means on CourseList.aspx page
check like

C#

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

if(id != "" or id != null)
{
    //do your code for what you whant that id.
}

Posted 4-Oct-11 22:51pm

Tejas Vaishnav

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Abhinav S · Accepted Answer · 2011-10-04T22:17:00

Solution 1

Make sure that Request.QueryString("CourseCatID") is not null.
If it is, then a ToString() on null will throw the error you are getting.

If you need more information on passing multiple values to a hyperlink field, see here[^].

Posted 4-Oct-11 22:17pm

Abhinav S

Updated 4-Oct-11 22:18pm

v3

sajithnet · Accepted Answer · 2011-10-04T22:23:00

Solution 2

ur passing PostBackUrl='<%#"CourseList.aspx?ID=" & Eval("CourseCatID")%> so use Request.QueryString("ID").ToString

Posted 4-Oct-11 22:23pm

sajithnet