Object reference not set to an instance of an object.

Question

0.00/5 (No votes)

See more:

C#

Object reference not set to an instance of an object.

protected void cmdSave_Click(object sender, EventArgs e)
    {
        string strNames = string.Empty;
        CheckBoxList Chkboxx = (CheckBoxList)PlaceHolder1.FindControl("Chkbox");
        foreach (ListItem em in Chkboxx.Items)  //-------- (Showing error)
        {
            if (em.Selected)
            {
                strNames += em.Value + ", ";
            }
        }

        string final_name = strNames.Substring(0, strNames.Length - 2);
        lblNames.Text = final_name;

    }

Actually I am adding Checkbox control dynamically :

C#

protected void ddl_varient_SelectedIndexChanged1(object sender, EventArgs e)
   {
       string query = "select prd_vrtyvalue_id,varient_value from tbl_ProductVariety_Value  where varient='" + ddl_varient.SelectedItem.Text + "' " +
                         " order by varient_value asc ";

    DataTable abc = new DataTable();
    SqlDataAdapter ada = new SqlDataAdapter(query, new CommonClass().connection());
       ada.Fill(abc);

       ChkboxList.ID = "Chkbox";
       for (int i = 0; i < abc.Rows.Count; i++)
       {
           ChkboxList.Items.Add(new ListItem(abc.Rows[i]["varient_value"].ToString(), abc.Rows[i]["prd_vrtyvalue_id"].ToString()));
       }
       ChkboxList.RepeatColumns = 2;
       PlaceHolder1.Controls.Add(ChkboxList);
   }

Can Anybody tell me what exactly i am doing wrong !

Posted 18-Mar-13 0:08am

Mas11

Updated 18-Mar-13 0:15am

v2

Add a Solution

Comments

Nitin S 18-Mar-13 6:09am

PlaceHolder1.FindControl("Chkbox") is returning null value, check whether that id exists in the placeholder

Chinmaya C 18-Mar-13 6:33am

yes.. I am also having same view as Nitin. :)
Need to check whether "Chkbox" control exists in the panel or not.

Mas11 18-Mar-13 6:15am

Please look on updated code !

Nitin S 18-Mar-13 6:41am

You wont be able to get the chkbox after clicking the save button as the viewstate of ChkboxList is no maintained by asp.net.
You have created an in-memory object of the checkboxlist class.

Mas11 18-Mar-13 6:44am

Ya exactly Nitin ! Sometimes I makes a silly mistakes. Anyway thanks a lot guys for your support :)

2 solutions

Solution 2

Hi,

You have add dynamic control at page load event not any selected change event...
so that when you call cmdSave_Click() event the previous created dynamic control are erased....

so you have redraw these control(dynamic) at page load event...then you can assign any value on it..

If you find this helpful, plz vote & Mark as Solution.
Thanks
Asp.Net C# Help Code[^]
Hemant Singh

Posted 18-Mar-13 0:35am

Hemant Singh Rautela

Updated 18-Mar-13 0:37am

v2

Comments

Mas11 18-Mar-13 6:39am

Ohh sh*t ! Thanks a lot I got it..

Mas11 18-Mar-13 6:44am

5* for it !

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

frostcox · Accepted Answer · 2013-03-18T00:20:00

Solution 1

Hey you need to loop through the place holder and check what items are inside, asp will create a different id that you expect

foreach(Control ctl in PlaceHolder1.Controls) { 
                                if(ctl is CheckBoxList) { 
                                        CheckBoxListlst cbl = (CheckBoxList)ctl; 
                                                                       } 
                        }

Hope this helps

Posted 18-Mar-13 0:20am

frostcox

Updated 18-Mar-13 0:23am

v4

Comments

Mas11 18-Mar-13 6:34am

Thanks for the answer! Now I know that after running your code that there was no control added in placeholder. But see in my code I was added it in the code : "PlaceHolder1.Controls.Add(ChkboxList)"

frostcox 18-Mar-13 6:41am

You need to re-create your control on every postback. Dynamic controls added to the page during a previous postback go to the garbage collector.

Mas11 18-Mar-13 6:44am

5* for it!

frostcox 18-Mar-13 6:50am

Glad I could help.