Object reference not set to an instance of an object Error in List

Question

Return this error "Object reference not set to an instance of an object Error" when trying to add item in list. In the other words it's return error in addtoNote.Add(Name); and am sure that Name is not null.

protected void features(string Name, string shortName)
{ List<string> addtoNote =  ViewState["Note"] as List<string> ;
    if (Name.Length > 0)
    {
        addtoNote.Add(Name);
    } else
    {for (int x = 0; x < addtoNote.Count; x++)
        {if (addtoNote[x].StartsWith(shortName))
            {
                addtoNote.RemoveAt(x);}
        } }
    ViewState["Note"] = addtoNote;
    TxtNote.Text = string.Join(TxtNote.Text , ",", addtoNote);
}
protected void ChkPersonalAccedent_CheckedChanged(object sender, EventArgs e)
{if (ChkPersonalAccedent.Checked == true)
    { features("حوادث شخصية", "حوادث شخصية");}
    else
     { features("", "حوادث شخصية"); }}

Please, for your own sanity, press Ctrl+K, D in Visual Studio to format your code. — CodeCaster, Jul 05 '15 at 16:40

score 1 · Accepted Answer · answered Jul 05 '15 at 16:32

1

If ViewState["Note"] is not a List<string>, this expression

ViewState["Note"] as List<string>;

will return null. So addtoNote is null and that is why the runtime exception is thrown.

answered Jul 05 '15 at 16:32

Glorfindel

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How to fix it , no ViewState["Note"] and List is same – rere Jul 05 '15 at 16:40
You can exclude null list from your `if` statement `if( Name.Length > 0 && addtoNote != null)` @rere – M.kazem Akhgary Jul 05 '15 at 17:21

Object reference not set to an instance of an object Error in List

1 Answers1