webforms : use infragistics webdropdown in updatepanel

问题

For your information (this was my original problem webforms : add dynamically in javascript option to a dropdownlist, solved thanks to ConnorsFan).

My goal is to having a infragistics dropdownlist enabling multi selection and at each selection I want an event fired server side without refreshing the whole page.

This is my aspx page :

<%@ Register assembly="Infragistics45.Web.v16.1, Version=16.1.20161.1000, Culture=neutral, PublicKeyToken=7dd5c3163f2cd0cb" namespace="Infragistics.Web.UI.ListControls" tagprefix="ig" %>

<asp:Content ID="BodyContent" ContentPlaceHolderID="MainContent" runat="server">
    <ig:WebDropDown ID="WebDropDown1" runat="server" Width="200px" OnSelectionChanged="WebDropDown1_SelectionChanged" EnableMultipleSelection="true" EnableClosingDropDownOnSelect="false" AutoPostBack="true">
</ig:WebDropDown>
<asp:UpdatePanel runat="server" UpdateMode="Conditional">
    <Triggers>
        <asp:AsyncPostBackTrigger ControlId="WebDropDown1" EventName="SelectionChanged"/>
    </Triggers>
</asp:UpdatePanel>

This is my code-behind page :

    private List<string> allPossiblechoices = new List<string>() { "a", "b", "c","d","e" };

    private List<string> defaultChoices = new List<string>() { "a", "b", "c" };

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!this.IsPostBack)
        {
            foreach(var choice in allPossiblechoices)
            {
                WebDropDown1.Items.Add(
                    new DropDownItem()
                    {
                        Text = choice,
                        Value = choice,
                        Selected = defaultChoices.Contains(choice)
                    }
                );
            }
        }
    }

    protected void WebDropDown1_SelectionChanged(object sender, DropDownSelectionChangedEventArgs e)
    {
         // I put a breakpoint here to see what e.NewSelection and e.OldSelection are
    }

By default, when the page is requested for the first time, the dropdown is composed of a,b,c,d,e and only a,b,c are selected.

When I select d, a request is indeed send to the server (I put a breakpoint in my event handler) and the results are correct :

EventArgs e.OldSelection contains a,b,c.
EventArgs e.NewSelection contains a,b,c,d.

Then, I deselect d and the results are the following :

EventArgs e.OldSelection contains a,b,c.d.
EventArgs e.NewSelection contains a,b,c,d.

I don't understand why EventArgs e.NewSelection contains d even if I deselected it.

The fact that it's even more strange, is that I have done the same thing without the updatePanel and everything works fine, the selection (new and old) are correct.

Thanks in advance for your help.

回答1:

You can call the RegisterStartupScript static method of the ScriptManager class to add some Javascript code to be executed after the event handler has returned. In the code below, I assume that the ID of the UpdatePanel is UpdatePanel1.

protected void WebDropDown1_SelectionChanged(object sender, DropDownSelectionChangedEventArgs e)
{
    WebDropDown wdd = sender as WebDropDown;
    string scriptCode = string.Format("document.getElementById('{0}').openDropDown();", wdd.ClientID);
    ScriptManager.RegisterStartupScript(UpdatePanel1, UpdatePanel1.GetType(), "WDDScript1", scriptCode, true);
}

If it works, you will probably see the WebDropDown closing/opening when the panel is updated (unfortunately).

来源：https://stackoverflow.com/questions/36967018/webforms-use-infragistics-webdropdown-in-updatepanel

标签

ASP.NET

webforms

infragistics