How Can I Handle This Problem...showing null reference exception was unhandle by user code

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2.00/5 (1 vote)

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C#

protected void btnsubmit_Click(object sender, EventArgs e)
        {
            string strSelectOptions = string.Empty;


            CheckBox ch = sender as CheckBox;
           
                if (ch.Checked)
                   
                    strSelectOptions += ch.Text + ",";

                if (strSelectOptions != string.Empty)
                {

                    strSelectOptions = strSelectOptions.Remove(strSelectOptions.Length - 1);
                    int pos = strSelectOptions.LastIndexOf(",");
                    if (pos != -1)
                    {
                        strSelectOptions = strSelectOptions.Remove(pos, 1);
                        strSelectOptions = strSelectOptions.Insert(pos, " & ");
                    }
                
                    lblresult.Text = "Selected Options:" + strSelectOptions;
                           }
                else
                {
                    lblresult.Text = "No Option Selected";
                }

            }

Posted 24-Jul-15 22:47pm

Member 11862296

Updated 24-Jul-15 22:59pm

Afzaal Ahmad Zeeshan

v3

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Afzaal Ahmad Zeeshan 25-Jul-15 4:59am

On which line? Did you try debugging the application?

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OriginalGriff · Answer 1 · 2015-07-24T23:26:00

Look at your code:

C#

protected void btnsubmit_Click(object sender, EventArgs e)
        {
            string strSelectOptions = string.Empty;


            CheckBox ch = sender as CheckBox;

                if (ch.Checked)

hat is a button click event handler, so the chances are that the sender is a button, not a CheckBox.
So this line:

C#

CheckBox ch = sender as CheckBox;

will set ch to null, and any attempt to use a property or method will fail with a null reference exception.

Probably, you need to re-think what you are doing, or use the CheckBox name directly instead of trying to use the sender parameter.