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Null reference in Control Designer

2 posts, 0 answered
  1. higgsy
    higgsy avatar
    336 posts
    05 Aug 2010
    25 Sep 2010
    Link to this post

    I've followed (in fact ive copied and pasted) Gabe's tutorial on Control Designers at:

    Problem is, even copied and pasted the code fails, at the following point:

    /// <summary>
        /// Executed automatically when the I'm done button is clicked in the Control Designer.
        /// </summary>
        public override void OnSaving()
            // Set the underlying control properties to the new values.
            ((CustomControlBase) DesignedControl).Text = TextBox1.Text;
            ((CustomControlBase) DesignedControl).Priority =
                (CustomControlBase.PriorityType) Enum.Parse(typeof(CustomControlBase.PriorityType), DropDownList1.SelectedValue);

    DropDownList1.SelectedValue is always empty and therefore the enum.parse throws an exception.

    I know the OnSaving method can get access to DropDownList1 because otherwise the following method would have thrown an error.

    protected virtual DropDownList DropDownList1 {
        get { return base.Container.GetControl<DropDownList>("DropDownList1", true); }

    Strangely, if i switch to the Advanced tab and select the dropdown from that list there is no error.

    Any help would be aprpeciated.

  2. Ivan Dimitrov
    Ivan Dimitrov avatar
    16072 posts
    12 Sep 2017
    26 Sep 2010
    Link to this post
    Hi Alastair,

    DropDownList1.SelectedValue is not valid string inside OnSaving and when you call  Enum.Parse Method and an  error is thrown. Try removing if (!Page.IsPostBack) during initialization

    Ivan Dimitrov
    the Telerik team
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2 posts, 0 answered