unable to access gridview html checkbox on button click event it's show "Object reference not set to an instance of an object."

Question

I am unable to access html checkbox on button click event.The checkbox is in gridview control.

<asp:GridView ID="_grvItems" runat="server"  />
              <Columns>
               <asp:TemplateField>
                        <ItemTemplate>

                            <input type="checkbox"  id="_chkSelect" />

                        </ItemTemplate>
                    </asp:TemplateField>

                </Columns>
                <PagerStyle CssClass="pgr" />
            </asp:GridView>

And I click on button then show me error "Object reference not set to an instance of an object." the code of button click event is :

 for (int i = 0; i < _grvItems.Rows.Count; i++)
    {
        HtmlInputCheckBox ch = (HtmlInputCheckBox)_grvItems.Rows[i].FindControl("_chkSelect");

        if (ch.Checked)
        {
            Response.Write("Checkbox is Checked");
        }}

Welcome to Stack Overflow! Almost all cases of `NullReferenceException` are the same. Please see "[What is a NullReferenceException in .NET?](http://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-in-net)" for some hints. — John Saunders, Oct 19 '13 at 15:41

score 0 · Answer 1 · answered Oct 19 '13 at 14:45

0

The FindControl method is not returning the checkbox but returning null. This is why you are getting "Object reference not set to an instance of an object." When you would be accessing Checked property. You need to put runat="server" to make checkbox server accessible.

Change

 <input type="checkbox"  id="_chkSelect" />

To

 <input type="checkbox"  id="_chkSelect" runat="server" />

answered Oct 19 '13 at 14:45

Adil

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Thanks for reply but when i put runat="server" than show me this error "The server tag is not well formed". – Mohammad Saleem Oct 19 '13 at 14:55
Actually i am already call javascript function on checkbox check event "');" />" – Mohammad Saleem Oct 19 '13 at 14:59
Adding runat="server" will make it accessible in code behind, whats wrong with that? Do you still have problem? – Adil Oct 19 '13 at 15:01
I have no clue what problem you have? – Adil Oct 19 '13 at 15:10

score 0 · Answer 2 · edited May 23 '17 at 11:57

0

I would suggest to check for null:

HtmlInputCheckBox ch = (HtmlInputCheckBox)_grvItems.Rows[i].FindControl("_chkSelect");

if (ch!= null && ch.Checked)
{
    Response.Write("Checkbox is Checked");
}}

EDIT (As Adil pointed:

I would also change in markup:

<asp:GridView ID="_grvItems" runat="server"  />
    <Columns>
        <asp:TemplateField>
            <ItemTemplate>    
                <input type="checkbox"  id="_chkSelect" runat="server" />    
            </ItemTemplate>
        </asp:TemplateField>        
    </Columns>
    <PagerStyle CssClass="pgr" />
</asp:GridView>

edited May 23 '17 at 11:57

Community

1
1

answered Oct 19 '13 at 16:29

afzalulh

7,925
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Please change in markup also as I have shown in edit, and let us know in which line you are getting error. – afzalulh Oct 19 '13 at 18:43

unable to access gridview html checkbox on button click event it's show "Object reference not set to an instance of an object."

2 Answers2