Populating an array with values from list check boxes

Question

I am trying to populate an array with values from check boxes. I am using list check boxes. I spent hours to find the error. I am getting NullReferenceException was unhandled by user code. The error is pointing to i++ bit of code. When I comment test[i]=item.Value; and i++; lines I can alert the values that are selected but I cannot add them into the array.

protected void Button1_Click(object sender, EventArgs e)
        {

        string []test=null;

        int i = 0;

        foreach (ListItem item in CheckBoxList1.Items)
        {

            if (item.Selected)
            {
                // oneSelected = true;

                test[i]=item.Value;
                i++;

                Response.Write("<script LANGUAGE='JavaScript' >alert('"+item.Value+"')</script>");

            }


        }
     }

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, Mar 11 '15 at 21:15

score 0 · Accepted Answer · answered Mar 11 '15 at 21:09

You need to instantiate the array but in order to do this you must have a size. I recommend using a List instead.

protected void Button1_Click(object sender, EventArgs e)
    {

    var test = new List<string>();

    foreach (ListItem item in CheckBoxList1.Items)
    {

        if (item.Selected)
        {
            // oneSelected = true;

            test.Add(item.Value);

            Response.Write("<script LANGUAGE='JavaScript' >alert('"+item.Value+"')</script>");

        }


    }
 }

Populating an array with values from list check boxes

1 Answers1