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POHow to maintain state in (asp.net) custom server control?
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copied!<p>I am trying to make a custom server control which inherits from DropDownList. I give the control an XML input containing some key/value pairs and my control shows them as a DropDownList. I make the list items in the override Render method like this:</p> <pre><code>foreach (XElement child in root.Elements("Choice")) { string title = child.Element("Title").Value; string score = child.Element("Score").Value; item = new ListItem(); item.Text = title; item.Value = score; this.Items.Add(item); } </code></pre> <p>The problem is that, when the user selects and item in the list, and the page posts back, the selected item is lost, and the list is re-initialized with the default data.</p> <p>Does anyone have any idea how to keep the selected item, i.e. maintain the state?</p> <p>Here is the complete source:</p> <pre><code>public class MultipleChoiceQuestionView2 : DropDownList </code></pre> <p>{ public MultipleChoiceQuestionView2() : base() { }</p> <p>protected override void Render(HtmlTextWriter writer) { writer.RenderBeginTag(HtmlTextWriterTag.Table); writer.RenderBeginTag(HtmlTextWriterTag.Tr);</p> <p>writer.RenderBeginTag(HtmlTextWriterTag.Td); #region Parse Contets if (!String.IsNullOrEmpty(this.Contents)) { XElement root = XElement.Parse(this.Contents);</p> <p>if (root.HasAttributes) { this.NoOfChoices = Int32.Parse(root.Attribute("ItemCount").Value); }</p> <p>this.Items.Clear(); this.Style.Add("width", "100px"); this.Style.Add("font-family", "Tahoma"); this.Items.Clear(); ListItem item = new ListItem(); item.Text = ""; item.Value = "0"; this.Items.Add(item);</p> <p>foreach (XElement child in root.Elements("Choice")) { string title = child.Element("Title").Value; string score = child.Element("Score").Value; item = new ListItem(); item.Text = title; item.Value = score;</p> <pre><code>this.Items.Add(item); </code></pre> <p>} } #endregion base.Render(writer); writer.RenderEndTag();</p> <p>if (this.Required) { RequiredFieldValidator rfv = new RequiredFieldValidator(); rfv.ControlToValidate = this.ID; rfv.InitialValue = "0"; rfv.Text = "*"; if (!String.IsNullOrEmpty(this.ValidationGroup)) { rfv.ValidationGroup = this.ValidationGroup; } writer.RenderBeginTag(HtmlTextWriterTag.Td); rfv.RenderControl(writer); writer.RenderEndTag(); }</p> <p>writer.RenderEndTag(); writer.RenderEndTag(); } #region Properties public string Contents { get { return ViewState["Contents"] == null ? "" : ViewState["Contents"].ToString(); } set { ViewState["Contents"] = value; } }</p> <p>private int mNoOfChoices; public int NoOfChoices { get { return mNoOfChoices; } set { mNoOfChoices = value; } }</p> <p>private string mValidationGroup; public string ValidationGroup { get { return mValidationGroup; } set { mValidationGroup = value; } }</p> <p>public string SelectedChoice { get { return ""; } }</p> <p>private bool mRequired = false; public bool Required { get { return mRequired; } set { mRequired = value; } }</p> <p>#endregion }</p> <p>Thanks in advance.</p>

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