[MVC] IEnumerable Extensions

 C#   MVC  

▌背景

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在MVC中，因時常會使用到將預設選項以IEnumerable<SelectListItem> 的型態Binding至DropDownList Helper，搜尋找到一版滿完整的IEnumerableExtensions，因此紀錄一下使用方式。 程式碼原始出處

▌練習

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▋View

<div class="col-md-10"> @Html.DropDownListFor(model => model.Sex, (IEnumerable<SelectListItem>)ViewData["SexSelectList"], new { htmlAttributes = new { @class = "form-control" } }) @Html.ValidationMessageFor(model => model.Sex, "", new { @class = "text-danger" }) </div>

▋IEnumerable Extensions

/// <summary>     /// IEnumerable Extensions     /// </summary>     public static class IEnumerableExtensions     {         /// <summary>         ///         /// </summary>         /// <param name="values"></param>         /// <returns></returns>         public static string JoinString(this IEnumerable<string> values)         {             return JoinString(values, ",");         }         /// <summary>         ///         /// </summary>         /// <param name="values"></param>         /// <param name="split"></param>         /// <returns></returns>         public static string JoinString(this IEnumerable<string> values, string split)         {             var result = values.Aggregate(string.Empty, (current, value) => current + (split + value));             result = result.TrimStart(split.ToCharArray());             return result;         }         /// <summary>         /// Do somthing for each item in the IEnumerable         /// </summary>         /// <typeparam name="T">Type</typeparam>         /// <param name="source">Source IEnumerable</param>         /// <param name="action">Action for doing something</param>         /// <returns>IEnumerable</returns>         public static IEnumerable<T> Each<T>(this IEnumerable<T> source, Action<T> action)         {             if (source != null)             {                 foreach (var item in source)                 {                     action(item);                 }             }             return source;         }         /// <summary>         /// Convert IEnumerable to IList<SelectListItem>         /// </summary>         /// <typeparam name="T">Type</typeparam>         /// <param name="source">IEnumerable</param>         /// <param name="text">Func for display text of IEnumerable</param>         /// <param name="value">Func for value of IEnumerable</param>         /// <returns>IList of SelectListItem</returns>         public static IList<SelectListItem> ToSelectList<T>(             this IEnumerable<T> source, Func<T, object> text, Func<T, object> value, bool isOrder = false)         {             return source.ToSelectList(text, value, null, null);         }         /// <summary>         /// Convert IEnumerable to IList<SelectListItem>         /// </summary>         /// <typeparam name="T">Type</typeparam>         /// <param name="source">IEnumerable</param>         /// <param name="text">Func for display text of IEnumerable</param>         /// <param name="value">Func for value of IEnumerabl</param>         /// <param name="optionalText">Extra option</param>         /// <returns>IList of SelectListItem</returns>         public static IList<SelectListItem> ToSelectList<T>(             this IEnumerable<T> source, Func<T, object> text, Func<T, object> value,             string optionalText, bool isOrder = false)         {             return source.ToSelectList(text, value, null, optionalText, isOrder);         }         /// <summary>         /// Convert IEnumerable to IList<SelectListItem>         /// </summary>         /// <typeparam name="T">Type</typeparam>         /// <param name="source">IEnumerable</param>         /// <param name="text">Func for display text of IEnumerable</param>         /// <param name="value">Func for value of IEnumerabl</param>         /// <param name="selected">Func for Seleced item</param>         /// <returns>IList of SelectListItem</returns>         public static IList<SelectListItem> ToSelectList<T>(             this IEnumerable<T> source, Func<T, object> text, Func<T, object> value,             Func<T, bool> selected, bool isOrder = false)         {             return source.ToSelectList(text, value, selected, null);         }         /// <summary>         /// Convert IEnumerable to IList<SelectListItem>         /// </summary>         /// <typeparam name="T">Type</typeparam>         /// <param name="source">IEnumerable</param>         /// <param name="text">Func for display text of IEnumerable</param>         /// <param name="value">Func for value of IEnumerabl</param>         /// <param name="selected">Func for Seleced item</param>         /// <param name="optionalText">Extra option</param>         /// <returns>IList of SelectListItem</returns>         public static IList<SelectListItem> ToSelectList<T>(             this IEnumerable<T> source, Func<T, object> text, Func<T, object> value,             Func<T, bool> selected, string optionalText, bool isOrder = false)         {             return source.ToSelectList(text, value, selected, optionalText, string.Empty, isOrder);         }         /// <summary>         /// Core function for EnumerableExtension.cs         /// </summary>         /// <typeparam name="T"></typeparam>         /// <param name="source"></param>         /// <param name="text"></param>         /// <param name="value"></param>         /// <param name="selected"></param>         /// <param name="optionalText"></param>         /// <param name="optionalValue"></param>         /// <returns></returns>         private static IList<SelectListItem> ToSelectList<T>(             this IEnumerable<T> source, Func<T, object> text, Func<T, object> value,             Func<T, bool> selected, string optionalText, string optionalValue, bool isOrder = false)         {             var items = new List<SelectListItem>();             //預設會先加入optionalText             if (!string.IsNullOrEmpty(optionalText))             {                 items.Insert(0, new SelectListItem() { Text = optionalText, Value = optionalValue });             }             if (source == null)             {                 return items;             }             foreach (var entity in source)             {                 var item = new SelectListItem();                 item.Text = text(entity).ToString();                 item.Value = value(entity).ToString();                 if (selected != null)                 {                     item.Selected = selected(entity);                 }                 if (item.Value != optionalValue)                 {                     items.Add(item);                 }             }             if (isOrder)             {                 items = items.OrderBy(d => d.Text).ToList();                        }             return items;         }     }

 ▋Controller

在Controller中自行建立（或拉回）有”Male”及”Female”的資料如下：

Key	Value
1	Male
2	Female

UnitTest codes in controller (Of course you have to comment out the non-testing codes by urself) :

public ActionResult Create() {             //Given "Text" and "Value" to the IList<SelectListItem>             ViewData["SexSelectList"] =                 sexList.AsEnumerable().ToSelectList(x => x.Value, x => x.Key);             //Set isOrder = true             ViewData["SexSelectList"] =                 sexList.AsEnumerable().ToSelectList(x => x.Value, x => x.Key, isOrder: true);             //Set the default selected value in IList<SelectListItem>             ViewData["SexSelectList"] =                 sexList.AsEnumerable().ToSelectList(x => x.Value, x => x.Key, x => x.Value.Equals("Female"));             //Add a new item : "Please select ..." to IList<SelectListItem>             ViewData["SexSelectList"] =                 sexList.AsEnumerable().ToSelectList(x => x.Value, x => x.Key, "Please select ...");             //Set the default selected value and add a new item in IList<SelectListItem>             ViewData["SexSelectList"] =                 sexList.AsEnumerable().ToSelectList(x => x.Value, x => x.Key, x => x.Value.Equals("Male"), "Please select ...");             //Do an action for every item in IList<SelectListItem>             ViewData["SexSelectList"] = sexList.AsEnumerable()                 .Each(x => x.Value = (x.Value.Equals("Male") ? (x.Value + "(男)") : (x.Value + "(女)")))                 .ToSelectList(x => x.Value, x => x.Key);             return View(); }

//Given "Text" and "Value" to the IList<SelectListItem>

//Set isOrder = true

//Set the default selected value in IList<SelectListItem>

//Add a new item : "Please select ..." to IList<SelectListItem>

//Set the default selected value and add a new item in IList<SelectListItem>

//Do an action for every item in IList<SelectListItem>