odject reference is not set error while trying to get ids of my HtmlAnchor

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Hi friends,

while I am trying to get all ids of my anchor tags I got an error "Object Reference is not set as Instance of an Object"
What i actually trying to do is:
In my aspx page i wrote code as,

<form id="form1" runat="server">
     <asp:Label ID="lblQues" runat="server" /><br />
    <asp:Button ID="btnAns" runat="server" Text="Get Anchor Ids" OnClick="btnAns_Click" /><br />
    <asp:Label ID="lblAns" runat="server" />  
    </form>

In my aspx.cs page i write code as,

 protected void Page_Load(object sender, EventArgs e)
        {           
            HtmlAnchor htmlAnchor = new HtmlAnchor();
            htmlAnchor.ID = "anchor";
            htmlAnchor.HRef = "#";
            htmlAnchor.InnerText = "anchor";
            lblQues.Controls.Add(htmlAnchor);
         }
 private string ids="";
 protected void btnAns_Click(object o, EventArgs a)
         {
             foreach (Control c in lblQues.Controls)
                 if (c is HtmlAnchor)
                 {
                    ids = ids+ " " + c.ID;
                     Type type = c.GetType();
                     string id = type.Name;
                  }
             lblAns.Text = ids;
         }

on button click i got an error as "Object Reference is not set as Instance of an Object" at c.ID.
Can you suggest how to do this.

Thanks,
Sindhu.

Posted 13-Feb-14 3:06am

Naga Sindhura

Updated 13-Feb-14 7:04am

v4

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Comments

Richard MacCutchan 13-Feb-14 9:14am

ids = ids.ToString()
What does ids refer to at this point?

Naga Sindhura 13-Feb-14 12:45pm

here ids reers to htmlAnchor.ID = "anchor"; that means all htmlAnchor id's

Richard MacCutchan 13-Feb-14 12:47pm

How do you figure that, since it is a local string variable that has not been initialised to anything?

Naga Sindhura 13-Feb-14 13:02pm

Hi Richard, I initialized a vale for string ids,still i am getting an error.

Richard MacCutchan 13-Feb-14 13:13pm

Please don't just tell us that you are getting "an error"; give us the full details, line of code, error type, variables involved, etc.

Naga Sindhura 13-Feb-14 13:19pm

Actually I assigned Id as 'anchor' to htmlAnchor. while getting that id i got an error at c.ID.

Richard MacCutchan 13-Feb-14 13:22pm

i got an error.
So I guess it's a secret then.

Richard MacCutchan 13-Feb-14 13:25pm

Use your debugger, step through the code and check the values of all variables, and their associated properties.

Naga Sindhura 13-Feb-14 13:27pm

Hi Richard MacCutchan,
Initially i tried with the code,
lblQues.Text = String.Concat("What is my <a name ='test' id='lnkMe' runat="server" href='#' >anchor name?");
here I am not able to get the control. so tried to add HtmlAnchor tag(both on page load).
I tied in this way that is not working or me. Is there any alternative to get the id's of all anchor tag.

4 solutions

Solution 1

Remove the .Tostring() from ids.
Please see the below code

C#

protected void btnAns_Click(object o, EventArgs a)
{
    foreach (Control c in lblQues.Controls)
         if (c is HtmlAnchor)
         {
            ids = ids + " " + c.ID;
             Type type = c.GetType();
             string id = type.Name;
          }
    lblAns.Text = ids;
}

Posted 13-Feb-14 3:25am

dharam1

Updated 13-Feb-14 6:48am

v3

Comments

Naga Sindhura 13-Feb-14 12:47pm

hi, i am getting an error (ids = ids + " " + c.ID;) because o c.ID) could you help me for this

Richard MacCutchan 13-Feb-14 12:49pm

Please use <pre> tags around your code snippets, as I have done on your behalf.

Richard MacCutchan 13-Feb-14 12:56pm

This won't work either. You cannot use ids in an expression before it has been initialised to some value.

Solution 2

Quote:
ids = ids.ToString() + " " + c.ID;

The Exception is due to ids, which is not defined anywhere.

Why are you using that? Correct your logic.

Posted 13-Feb-14 4:17am

Tadit Dash (ତଡିତ୍ କୁମାର ଦାଶ)

Comments

Naga Sindhura 13-Feb-14 12:55pm

hi, globally i created variable for ids as string. i am getting an error because of c.ID.

Tadit Dash (ତଡିତ୍ କୁମାର ଦାଶ) 13-Feb-14 13:17pm

That may be globally declared, but does it contain any value? Check by putting a debugger in this event only.
Also check if C.ID contains any data or not.

Solution 3

Change your code to:

C#

private string ids;
protected void btnAns_Click(object o, EventArgs a)
{
    ids = "";
    foreach (Control c in lblQues.Controls)
        if (c is HtmlAnchor)
        {
            ids += " " + c.ID;

            // what are these two lines supposed to do?
            Type type = c.GetType();
            string id = type.Name;
        }
    lblAns.Text = ids;
}

Posted 13-Feb-14 7:01am

Richard MacCutchan

Comments

Naga Sindhura 13-Feb-14 13:08pm

Hi Richard MacCutchan, i tried to get id name of all htmlAnchor using Type. Actually that is not required.

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Naga Sindhura · Accepted Answer · 2014-02-14T01:07:00

Solution 4

Thanks to all I got the Answer for my question

foreach (Control c in lblQues.Controls)
                 if (c is HtmlAnchor)
                 {       
                     string pp = c.ClientID;
                     ids = ids + " " + pp;
                 }

Posted 14-Feb-14 1:07am

Naga Sindhura