/// <summary>
/// Create a dropdownlist whose display will depend on a parent dropdownlist
/// </summary>
/// <param name="htmlHelper">The HTML helper</param>
/// <param name="name">The name of the form field to return</param>
/// <param name="selectList">A collection of System.Web.Mvc.SelectListItem objects that are used to populate the drop-down list</param>
/// <param name="optionLabel">The text for a default empty item. This parameter can be null</param>
/// <param name="htmlAttributes">An object that contains the HTML attributes to set for the element</param>
/// <param name="listType">automaticaly add the javascript for a type of list</param>
/// <returns>An HTML select element with an option subelement for each item in the list</returns>
public static MvcHtmlString CascadingDropDownList(this HtmlHelper htmlHelper, string name, IEnumerable <CascadingSelectListItem> selectList, string optionLabel, object htmlAttributes = null, CascadingDropDownListType listType = CascadingDropDownListType.ChildList)
{
MvcHtmlString mvcHtmlString = htmlHelper.DropDownList(name, selectList, optionLabel, htmlAttributes);
string dropDownListId = name;
return(CascadingDropDownList(htmlHelper, selectList, optionLabel, mvcHtmlString, dropDownListId, listType));
}
/// <summary>
/// Create a dropdownlist whose display will depend on a parent dropdownlist
/// </summary>
/// <param name="htmlHelper">The HTML helper</param>
/// <param name="selectList">A collection of System.Web.Mvc.SelectListItem objects that are used to populate the drop-down list</param>
/// <param name="optionLabel">The text for a default empty item. This parameter can be null</param>
/// <param name="mvcHtmlString">An HTML select element with an option subelement for each item</param>
/// <param name="dropDownListId">The id of the form field to return</param>
/// <param name="listType">automaticaly add the javascript for a type of list</param>
/// <returns>An HTML select element with an option subelement for each item in the list</returns>
private static MvcHtmlString CascadingDropDownList(HtmlHelper htmlHelper, IEnumerable <CascadingSelectListItem> selectList, string optionLabel, MvcHtmlString mvcHtmlString, string dropDownListId, CascadingDropDownListType listType)
{
XDocument selectDoc = XDocument.Parse(mvcHtmlString.ToString());
string prefixDataAttr = "data-";
string prefixIdAttr = "id-";
string separator = "|";
List <XElement> options = selectDoc.Element("select").Descendants().ToList();
if (options != null && options.Any())
{
foreach (XElement option in options)
{
CascadingSelectListItem cascadingItem = null;
if (option.Attributes("value").FirstOrDefault() != null)
{
cascadingItem = selectList.FirstOrDefault(x => x.Value == option.Attributes("value").First().Value);
}
if (cascadingItem != null)
{
foreach (var parentValue in cascadingItem.ParentValues)
{
option.SetAttributeValue(prefixIdAttr + parentValue.Key, parentValue.Key);
option.SetAttributeValue(prefixDataAttr + parentValue.Key, string.Join(separator, parentValue.Value));
}
}
else if (option.Value == optionLabel)
{
List <string> parentIds = selectList.SelectMany(x => x.ParentValues.Select(y => y.Key)).Distinct().ToList();
if (parentIds != null && parentIds.Any())
{
parentIds.Sort();
foreach (var parentId in parentIds)
{
List <string> parentValues = selectList.SelectMany(x => x.ParentValues.Where(z => z.Key == parentId).SelectMany(y => y.Value)).Distinct().ToList();
if (parentValues != null && parentValues.Any())
{
parentValues.Sort();
option.SetAttributeValue(prefixIdAttr + parentId, parentId);
option.SetAttributeValue(prefixDataAttr + parentId, string.Join(separator, parentValues));
}
}
}
}
}
}
if (listType == CascadingDropDownListType.ChildList)
{
string javascript = "<script type=\"text/javascript\">$(document).ready(function() { $(\"#" + dropDownListId + "\").cascadingDropDownList(); });</script>";
htmlHelper.Script(javascript, HtmlHelpersScript.Priority.FastRender);
}
return(MvcHtmlString.Create(selectDoc.ToString()));
}
/// <summary>
/// Create a dropdownlist whose display will depend on a parent dropdownlist
/// </summary>
/// <typeparam name="TModel">The type of the model</typeparam>
/// <typeparam name="TProperty">The type of the property</typeparam>
/// <param name="htmlHelper">The HTML helper</param>
/// <param name="expression">An expression that identifies the object that contains the properties to display</param>
/// <param name="selectList">A collection of System.Web.Mvc.SelectListItem objects that are used to populate the drop-down list</param>
/// <param name="optionLabel">The text for a default empty item. This parameter can be null</param>
/// <param name="htmlAttributes">An object that contains the HTML attributes to set for the element</param>
/// <param name="listType">automaticaly add the javascript for a type of list</param>
/// <returns>An HTML select element for each property in the object that is represented by the expression</returns>
public static MvcHtmlString CascadingDropDownListFor <TModel, TProperty>(this HtmlHelper <TModel> htmlHelper, Expression <Func <TModel, TProperty> > expression, IEnumerable <CascadingSelectListItem> selectList, string optionLabel, object htmlAttributes = null, CascadingDropDownListType listType = CascadingDropDownListType.ChildList)
{
MvcHtmlString mvcHtmlString = htmlHelper.DropDownListFor(expression, selectList, optionLabel, htmlAttributes);
string dropDownListId = htmlHelper.IdFor(expression).ToString();
return(CascadingDropDownList(htmlHelper, selectList, optionLabel, mvcHtmlString, dropDownListId, listType));
}
