Question

我正在尝试在ASP.NET MVC4中创建级联下拉列表，我的下拉列表的两个值都来自方法，因此如何将值从一个下拉列表传递给另一个下拉列表。

以下是我获取第一个下拉列表的值的方法：

var CampaignInfo1 = CampaignManagementService.GetAdvertisers((string)Session["ticket"]);
List<CampaignList1> items1 = new List<CampaignList1>();
foreach (var element in CampaignInfo1)
{
    items1.Add(new CampaignList1() { ID1 = element.Key, Name1 = element.Value });
}
var listOfCamp1 = new SelectList(items1, "ID1", "Name1", 1);
ViewData["list1"] = listOfCamp1;

视图中的下拉列表：

@Html.DropDownList("list1", ViewData["list1"] as SelectList, "-- Select Client -1-")

第二个下拉列表值的方法几乎相同：

var CampaignInf = CampaignManagementService.GetCampaigns((string)Session["ticket"], IDFromfirstDDL);
List<AlreadyCreatedCampaignList> itemas = new List<AlreadyCreatedCampaignList>();
foreach (var element in CampaignInf)
{
    itemas.Add(new AlreadyCreatedCampaignList() { campID = element.Key, campName = element.Value });
}
var listOfCam = new SelectList(itemas, "campID", "campName", 1);
ViewData["clist"] = listOfCam;

但是有一个问题是在方法GetCampaigns中我必须传递我从第一个DDL获得的id（IDFromfirstDDL），然后才返回该id的值。问题是我不知道如何将所选值从第一个DDL传递到第二个，没有任何表单提交，因为我需要第二个DDL在第一次DDL更改后立即更改其值。

Answer 1

我结合了http://kruisit.nl/articles/asp.net-mvc-linked-dropdown/和http://www.appelsiini.net/projects/chained jquery链式选择器这篇文章

目前在我的网站上使用

public static class LinkedDropdownHelper
        {
            #region Methods

            public static MvcHtmlString LinkedDropdownListFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression, string parent, IEnumerable<LinkedSelectListItem> selectList ,bool removedefault=false)
            {
                ModelMetadata metadata = ModelMetadata.FromLambdaExpression( expression,htmlHelper.ViewData );
                var selectedvalue = metadata.Model;
                string propertyName = metadata.PropertyName; 
                TagBuilder select = new TagBuilder("select");
                select.Attributes.Add("id", propertyName);
                select.Attributes.Add("name", propertyName);
                //select.Attributes.Add("class", "linked-dropdown");
                select.Attributes.Add("class", parent);

                foreach (var item in selectList)
                {
                    if (removedefault && item.Value == "-1")
                    {
                        //skip default
                    }
                    else
                    {
                        TagBuilder option = new TagBuilder("option");
                        option.InnerHtml = item.Text;
                        option.Attributes.Add("value", item.Value);
                        option.Attributes.Add("class", item.LinkValue);

                        if (item.Selected)
                        {
                            option.Attributes.Add("selected", "selected");
                        }
                        select.InnerHtml += option.ToString(TagRenderMode.Normal);
                    }
                }
                //below code was changed by abdurrauf to support jquery chains 
                string script = @"<script type='text/javascript'>$(document).bind('ready',  function(){
            $('#" + propertyName + "').chained('#" + parent + "');"+
                   @"$('select[name=""" + propertyName + @"""]').val("""+selectedvalue+@""");" +
                  "});</script>";

                return MvcHtmlString.Create(script + select.ToString(TagRenderMode.Normal));
            }

            #endregion Methods
        }

        public class LinkedSelectList : IEnumerable<LinkedSelectListItem>
        {
            #region Constructors

            public LinkedSelectList(IEnumerable items, string dataValueField, string dataTextField, string dataLinkedValueField, IEnumerable selectedValues)
            {
                if (items == null)
                {
                    throw new ArgumentNullException("items");
                }

                Items = items;
                DataValueField = dataValueField;
                DataTextField = dataTextField;
                DataLinkedValueField = dataLinkedValueField;
                SelectedValues = selectedValues;
            }

            #endregion Constructors

            #region Properties

            public string DataLinkedValueField
            {
                get; private set;
            }

            public string DataTextField
            {
                get; private set;
            }

            public string DataValueField
            {
                get; private set;
            }

            public IEnumerable Items
            {
                get; private set;
            }

            public IEnumerable SelectedValues
            {
                get; private set;
            }

            #endregion Properties

            #region Methods

            public virtual IEnumerator<LinkedSelectListItem> GetEnumerator()
            {
                return GetListItems().GetEnumerator();
            }

            IEnumerator IEnumerable.GetEnumerator()
            {
                return GetEnumerator();
            }

            internal IList<LinkedSelectListItem> GetListItems()
            {
                return GetListItemsWithValueField();
            }

            private static string Eval(object container, string expression)
            {
                object value = container;
                if (!String.IsNullOrEmpty(expression))
                {
                    value = DataBinder.Eval(container, expression);
                }
                return Convert.ToString(value, CultureInfo.CurrentCulture);
            }

            private IList<LinkedSelectListItem> GetListItemsWithValueField()
            {
                HashSet<string> selectedValues = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
                if (SelectedValues != null)
                {
                    selectedValues.UnionWith(from object value in SelectedValues select Convert.ToString(value, CultureInfo.CurrentCulture));
                }

                var listItems = from object item in Items
                                let value = Eval(item, DataValueField)
                                select new LinkedSelectListItem
                                {
                                    Value = value,
                                    Text = Eval(item, DataTextField),
                                    LinkValue = Eval(item, DataLinkedValueField),
                                    Selected = selectedValues.Contains(value)
                                };
                return listItems.ToList();
            }

            #endregion Methods
        }

        public class LinkedSelectListItem
        {
            #region Properties

            public string LinkValue
            {
                get; set;
            }

            public bool Selected
            {
                get; set;
            }

            public string Text
            {
                get; set;
            }

            public string Value
            {
                get; set;
            }

            #endregion Properties
        }

制作级联下拉列表

1 个答案: