jquery - 使用 JavaScript 以编程方式触发 ASP.net CascadingDropDown 更改事件的正确方法

Question

标记

<asp:ScriptManager runat="server" />
Country Code
<asp:TextBox ID="CoutryCodeTextBox" runat="server" onblur="selectCountry(this.id);">
</asp:TextBox>

<asp:DropDownList ID="CountryDropDownList" runat="server">
</asp:DropDownList>

<ajaxToolkit:CascadingDropDown
    ID="CountryDropDownListCascadingDropDown" runat="server"
    TargetControlID="CountryDropDownList"
    Category="Country"
    ServiceMethod="GetCountries"
    ServicePath="~/CountryData.asmx"
    LoadingText="Loading ..."
    PromptText="SELECT">
</ajaxToolkit:CascadingDropDown>


<asp:DropDownList ID="CityDropDownList" runat="server">
</asp:DropDownList>
<ajaxToolkit:CascadingDropDown
    ID="CityDropDownListCascadingDropDown" runat="server"
    ParentControlID="CountryDropDownList"
    TargetControlID="CityDropDownList"
    Category="City" ServiceMethod="GetCities"
    ServicePath="~/CountryData.asmx"
    LoadingText="Loading ..."
    PromptText="SELECT">
</ajaxToolkit:CascadingDropDown>

Web 服务 (~/CountryData.asmx)

[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
[System.ComponentModel.ToolboxItem(false)]
[ScriptService]
public class CountryData : System.Web.Services.WebService
{
    [WebMethod]
    public CascadingDropDownNameValue[] GetCountries(string knownCategoryValues, string category)
    {
        List<CascadingDropDownNameValue> values = new List<CascadingDropDownNameValue>();

        values.Add(new CascadingDropDownNameValue("United States", "US"));
        values.Add(new CascadingDropDownNameValue("Canada", "CA"));

        return values.ToArray();
    }

    [WebMethod]
    public CascadingDropDownNameValue[] GetCities(string knownCategoryValues, string category)
    {
        StringDictionary kv = CascadingDropDown.ParseKnownCategoryValuesString(knownCategoryValues);
        string country = kv["Country"];

        List<CascadingDropDownNameValue> values = new List<CascadingDropDownNameValue>();

        switch (country)
        { 
            case "US":
                values.Add(new CascadingDropDownNameValue("California", "CA"));
                values.Add(new CascadingDropDownNameValue("New York", "NY"));
                break;
            case "CA":
                values.Add(new CascadingDropDownNameValue("Toronto", "TO"));
                values.Add(new CascadingDropDownNameValue("Montreal", "MO"));
                break;
        }

        return values.ToArray();
    }

}

jQuery

    var selectCountry = function (id)
    {
        var countryCodeTextBox = $("#" + id);
        var countryDropDownList = $("#CountryDropDownList");

        countryDropDownList.val(countryCodeTextBox.val());
        countryDropDownList.change();
    }

JavaScript 函数更改 CountryDropDownList 的选定值。但是，级联控件 CityDropDownList 不会自动填充。

使用 jQuery 触发父控件中的更改事件以便相关控件自动级联的正确方法是什么？

Answer 1

根据您的说法，my answer on How can I trigger an onchange event manually?也解决了您的问题:

There's a couple of ways you can do this. If the onchange listener is a function set via the element.onchange property and you're not bothered about the event object or bubbling/propagation, the easiest method is to just call that function:

element.onchange();

If you need it to simulate the real event in full, or if you set the event via the html attribute or addEventListener/attachEvent, you need to do a bit of feature detection to correctly fire the event:

if ("createEvent" in document) {
    var evt = document.createEvent("HTMLEvents");
    evt.initEvent("change", false, true);
    element.dispatchEvent(evt);
}
else
    element.fireEvent("onchange");