Razor 语法@Html.DropDownList，根据List集合或者枚举生成Select标签
1、根据List集合生成Select标签，根据数据库数据换成SelectListItem集合
Action 方法（也可使用下方的List集合的扩展方法）：
1 var selectList = DBList.Select(f => new SelectListItem { Value = f.Key, Text = f.Value }).ToList(); 2 selectList.Insert(0, new SelectListItem() { Value = "-1", Text = "请选择" }); 3 ViewData["selectList"] = selectList;
View视图：
1 @Html.DropDownListFor(m => m.HandleBy, ViewData["selectList"] as IEnumerable<SelectListItem>, new { @class = "form-control selectWidth" })
2、根据枚举扩展方法生成Select标签
View视图：
@Html.DropDownList("ContractStyle", new Model.Enums.ContractStyleType().ToSelectList(), "全部", new { @class = "form-control" })
扩展方法：
1 public static class SelectListExtension 2 { 3 public static IEnumerable<SelectListItem> CreateRangeSelect(int nimNumber, int maxNumber, string formatter = null) 4 { 5 for (int i = nimNumber; i <= maxNumber; i++) 6 yield return new SelectListItem { Value = i.ToString(formatter), Text = i.ToString(formatter) }; 7 } 8 9 public static IEnumerable<SelectListItem> ToSelectListItem(this Dictionary<int, string> items, string defaultValue = null) 10 { 11 if (!string.IsNullOrWhiteSpace(defaultValue)) 12 yield return new SelectListItem { Value = "", Text = defaultValue }; 13 14 foreach (var item in items) 15 yield return new SelectListItem { Value = item.Key.ToString(), Text = item.Value }; 16 } 17 18 public static SelectList ToSelectList<TEnum>(this TEnum enumObj) 19 where TEnum : struct, IComparable, IFormattable, IConvertible 20 { 21 var values = from TEnum e in Enum.GetValues(typeof(TEnum)) 22 select new { Id = Convert.ToInt32(e), Name = GetEnumDescription(e) }; 23 return new SelectList(values, "Id", "Name"); 24 } 25 26 /// <summary>将枚举类型转化为SelectListItem列表 27 /// </summary> 28 /// <typeparam name="TEnum"></typeparam> 29 /// <param name="enumObject">The enum object.</param> 30 /// <param name="firstItemText">The first item text.</param> 31 /// <param name="selectedId">The selected identifier.</param> 32 /// <returns></returns> 33 public static List<SelectListItem> EnumToSelectListItems<TEnum>(string firstItemText = null, int selectedId = -1) 34 { 35 var selectList = new List<SelectListItem>(); 36 37 if (!string.IsNullOrEmpty(firstItemText)) 38 { 39 selectList.Add(new SelectListItem() 40 { 41 Value = "-1", 42 Text = firstItemText, 43 Selected = selectedId == -1 44 }); 45 } 46 selectList.AddRange(from TEnum e in Enum.GetValues(typeof(TEnum)) 47 select new SelectListItem 48 { 49 Value = Convert.ToInt32(e).ToString(), 50 Text = GetEnumDescription(e), 51 Selected = Convert.ToInt32(e) == selectedId 52 }); 53 54 return selectList; 55 } 56 public static List<SelectListItem> ToSelectListByFieldType<TEnum>(FieldTypeEnum? fieldType = null, string firstItemText = null, string firstItemValue = null, int selectedId = -1) 57 where TEnum : struct, IComparable, IFormattable, IConvertible 58 { 59 var selectList = new List<SelectListItem>(); 60 61 if (!string.IsNullOrEmpty(firstItemText)) 62 { 63 selectList.Add(new SelectListItem() 64 { 65 Value = firstItemValue, 66 Text = firstItemText, 67 Selected = selectedId == -1 68 }); 69 } 70 if (fieldType.HasValue)//指定枚举字段类型,只返回特定类型列表 71 { 72 foreach (TEnum e in Enum.GetValues(typeof(TEnum))) 73 { 74 FieldInfo fi = e.GetType().GetField(e.ToString()); 75 EnumValueFieldTypeAttribute[] fieldTypeAttributes = (EnumValueFieldTypeAttribute[])fi.GetCustomAttributes(typeof(EnumValueFieldTypeAttribute), false); 76 if (fieldTypeAttributes == null || fieldTypeAttributes.Length == 0 || fieldTypeAttributes[0].FieldType != fieldType) continue; 77 var item = new SelectListItem 78 { 79 Value = Convert.ToInt32(e).ToString(), 80 Selected = Convert.ToInt32(e) == selectedId 81 }; 82 DescriptionAttribute[] attributes = (DescriptionAttribute[])fi.GetCustomAttributes(typeof(DescriptionAttribute), false); 83 if ((attributes != null) && (attributes.Length > 0)) 84 item.Text = attributes[0].Description; 85 else 86 item.Text = e.ToString(); 87 selectList.Add(item); 88 } 89 } 90 else//不指定枚举字段类型，显示全部 91 { 92 selectList.AddRange(from TEnum e in Enum.GetValues(typeof(TEnum)) 93 select new SelectListItem 94 { 95 Value = Convert.ToInt32(e).ToString(), 96 Text = GetEnumDescription(e), 97 Selected = Convert.ToInt32(e) == selectedId 98 }); 99 } 100 return selectList; 101 } 102 public static string GetEnumDescription<TEnum>(TEnum value) 103 { 104 FieldInfo fi = value.GetType().GetField(value.ToString()); 105 106 DescriptionAttribute[] attributes = (DescriptionAttribute[])fi.GetCustomAttributes(typeof(DescriptionAttribute), false); 107 108 if ((attributes != null) && (attributes.Length > 0)) 109 return attributes[0].Description; 110 else 111 return value.ToString(); 112 } 113 114 /// <summary>将list转换成SelectListItem列表 115 /// </summary> 116 /// <typeparam name="T"></typeparam> 117 /// <param name="list">列表数据</param> 118 /// <param name="firstItemText">第一个下拉框名称（未空则不额外添加）</param> 119 /// <param name="selectedId">已选项id</param> 120 public static IEnumerable<SelectListItem> ListToSelectListItems<T>(this IEnumerable<T> list, string firstItemText, int selectedId = -1) 121 { 122 if (list == null) 123 { 124 return new List<SelectListItem>(); 125 } 126 var t = typeof(T); 127 List<SelectListItem> selectList = new List<SelectListItem>(); 128 if (!string.IsNullOrEmpty(firstItemText)) 129 { 130 selectList.Add(new SelectListItem() 131 { 132 Value = "-1", 133 Text = firstItemText, 134 Selected = selectedId == -1 135 }); 136 } 137 foreach (var item in list) 138 { 139 var addItem = new SelectListItem(); 140 foreach (var p in t.GetProperties()) 141 { 142 //id（约定为int类型） 143 if (p.PropertyType == typeof(System.Int32)) 144 { 145 addItem.Value = p.GetValue(item).ToString(); 146 } 147 else 148 {//value 149 addItem.Text = p.GetValue(item).ToString(); 150 } 151 addItem.Selected = addItem.Value.Equals(selectedId); 152 } 153 selectList.Add(addItem); 154 } 155 return selectList; 156 } 157 158 159 }
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