MVC进阶学习--View和Controller之间的数据传递(一)

1.使用ViewData

　　ViewData 的是ControllerBase 的一个属性,是一个数据字典类型的，其实现代码如(这段代码来自asp.net MVC开源项目中源码)下:

Code
  1 public class ViewDataDictionary : IDictionary<string, object> {
  2 
  3         private readonly Dictionary<string, object> _innerDictionary = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
  4         private object _model;
  5         private readonly ModelStateDictionary _modelState = new ModelStateDictionary();
  6 
  7         public ViewDataDictionary()
  8             : this((object)null) {
  9         }
 10 
 11         [SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors",
 12             Justification = "See note on SetModel() method.")]
 13         public ViewDataDictionary(object model) {
 14             Model = model;
 15         }
 16 
 17         [SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors",
 18             Justification = "See note on SetModel() method.")]
 19         public ViewDataDictionary(ViewDataDictionary dictionary) {
 20             if (dictionary == null) {
 21                 throw new ArgumentNullException("dictionary");
 22             }
 23 
 24             foreach (var entry in dictionary) {
 25                 _innerDictionary.Add(entry.Key, entry.Value);
 26             }
 27             foreach (var entry in dictionary.ModelState) {
 28                 ModelState.Add(entry.Key, entry.Value);
 29             }
 30             Model = dictionary.Model;
 31         }
 32 
 33         [SuppressMessage("Microsoft.Security", "CA2123:OverrideLinkDemandsShouldBeIdenticalToBase")]
 34         public int Count {
 35             get {
 36                 return _innerDictionary.Count; 37             } 38         } 39  40         [SuppressMessage("Microsoft.Security", "CA2123:OverrideLinkDemandsShouldBeIdenticalToBase")] 41         public bool IsReadOnly { 42             get { 43                 return ((IDictionary<string, object>)_innerDictionary).IsReadOnly; 44             } 45         } 46  47         [SuppressMessage("Microsoft.Security", "CA2123:OverrideLinkDemandsShouldBeIdenticalToBase")] 48         public ICollection<string> Keys { 49             get { 50                 return _innerDictionary.Keys; 51             } 52         } 53  54         public object Model { 55             get { 56                 return _model; 57             } 58             set { 59                 SetModel(value); 60             } 61         } 62  63         public ModelStateDictionary ModelState { 64             get { 65                 return _modelState; 66             } 67         } 68  69         [SuppressMessage("Microsoft.Security", "CA2123:OverrideLinkDemandsShouldBeIdenticalToBase")] 70         public object this[string key] { 71             get { 72                 object value; 73                 _innerDictionary.TryGetValue(key, out value); 74                 return value; 75             } 76             set { 77                 _innerDictionary[key] = value; 78             } 79         } 80  81         [SuppressMessage("Microsoft.Security", "CA2123:OverrideLinkDemandsShouldBeIdenticalToBase")] 82         public ICollection<object> Values { 83             get { 84                 return _innerDictionary.Values; 85             } 86         } 87  88         [SuppressMessage("Microsoft.Security", "CA2123:OverrideLinkDemandsShouldBeIdenticalToBase")] 89         public void Add(KeyValuePair<string, object> item) { 90             ((IDictionary<string, object>)_innerDictionary).Add(item); 91         } 92  93         [SuppressMessage("Microsoft.Security", "CA2123:OverrideLinkDemandsShouldBeIdenticalToBase")] 94         public void Add(string key, object value) { 95             _innerDictionary.Add(key, value); 96         } 97  98         [SuppressMessage("Microsoft.Security", "CA2123:OverrideLinkDemandsShouldBeIdenticalToBase")] 99         public void Clear() {100             _innerDictionary.Clear();101         }102 103         [SuppressMessage("Microsoft.Security", "CA2123:OverrideLinkDemandsShouldBeIdenticalToBase")]104         public bool Contains(KeyValuePair<string, object> item) {105             return ((IDictionary<string, object>)_innerDictionary).Contains(item);106         }107 108         [SuppressMessage("Microsoft.Security", "CA2123:OverrideLinkDemandsShouldBeIdenticalToBase")]109         public bool ContainsKey(string key) {110             return _innerDictionary.ContainsKey(key);111         }112 113         [SuppressMessage("Microsoft.Security", "CA2123:OverrideLinkDemandsShouldBeIdenticalToBase")]114         public void CopyTo(KeyValuePair<string, object>[] array, int arrayIndex) {115             ((IDictionary<string, object>)_innerDictionary).CopyTo(array, arrayIndex);116         }117 118         [SuppressMessage("Microsoft.Naming", "CA1704:IdentifiersShouldBeSpelledCorrectly", MessageId = "Eval",119             Justification = "Commonly used shorthand for Evaluate.")]120         public object Eval(string expression) {121             if (String.IsNullOrEmpty(expression)) {122                 throw new ArgumentException(MvcResources.Common_NullOrEmpty, "expression");123             }124 125             return ViewDataEvaluator.Eval(this, expression);126         }127 128         [SuppressMessage("Microsoft.Naming", "CA1704:IdentifiersShouldBeSpelledCorrectly", MessageId = "Eval",129             Justification = "Commonly used shorthand for Evaluate.")]130         public string Eval(string expression, string format) {131             object value = Eval(expression);132 133             if (value == null) {134                 return String.Empty;135             }136 137             if (String.IsNullOrEmpty(format)) {138                 return Convert.ToString(value, CultureInfo.CurrentCulture);139             }140             else {141                 return String.Format(CultureInfo.CurrentCulture, format, value);142             }143         }144 145         [SuppressMessage("Microsoft.Security", "CA2123:OverrideLinkDemandsShouldBeIdenticalToBase")]146         public IEnumerator<KeyValuePair<string, object>> GetEnumerator() {147             return _innerDictionary.GetEnumerator();148         }149 150         [SuppressMessage("Microsoft.Security", "CA2123:OverrideLinkDemandsShouldBeIdenticalToBase")]151         public bool Remove(KeyValuePair<string, object> item) {152             return ((IDictionary<string, object>)_innerDictionary).Remove(item);153         }154 155         [SuppressMessage("Microsoft.Security", "CA2123:OverrideLinkDemandsShouldBeIdenticalToBase")]156         public bool Remove(string key) {157             return _innerDictionary.Remove(key);158         }159 160         // This method will execute before the derived type's instance constructor executes. Derived types must161         // be aware of this and should plan accordingly. For example, the logic in SetModel() should be simple162         // enough so as not to depend on the "this" pointer referencing a fully constructed object.163         protected virtual void SetModel(object value) {164             _model = value;165         }166 167         [SuppressMessage("Microsoft.Security", "CA2123:OverrideLinkDemandsShouldBeIdenticalToBase")]168         public bool TryGetValue(string key, out object value) {169             return _innerDictionary.TryGetValue(key, out value);170         }171 172         internal static class ViewDataEvaluator {173             public static object Eval(ViewDataDictionary vdd, string expression) {174                 //Given an expression "foo.bar.baz" we look up the following (pseudocode):175                 //  this["foo.bar.baz.quux"]176                 //  this["foo.bar.baz"]["quux"]177                 //  this["foo.bar"]["baz.quux]178                 //  this["foo.bar"]["baz"]["quux"]179                 //  this["foo"]["bar.baz.quux"]180                 //  this["foo"]["bar.baz"]["quux"]181                 //  this["foo"]["bar"]["baz.quux"]182                 //  this["foo"]["bar"]["baz"]["quux"]183 184                 object evaluated = EvalComplexExpression(vdd, expression);185                 return evaluated;186             }187 188             private static object EvalComplexExpression(object indexableObject, string expression) {189                 foreach (ExpressionPair expressionPair in GetRightToLeftExpressions(expression)) {190                     string subExpression = expressionPair.Left;191                     string postExpression = expressionPair.Right;192 193                     object subtarget = GetPropertyValue(indexableObject, subExpression);194                     if (subtarget != null) {195                         if (String.IsNullOrEmpty(postExpression))196                             return subtarget;197 198                         object potential = EvalComplexExpression(subtarget, postExpression);199                         if (potential != null) {200                             return potential;201                         }202                     }203                 }204                 return null;205             }206 207             private static IEnumerable<ExpressionPair> GetRightToLeftExpressions(string expression) {208                 // Produces an enumeration of all the combinations of complex property names209                 // given a complex expression. See the list above for an example of the result210                 // of the enumeration.211 212                 yield return new ExpressionPair(expression, String.Empty);213 214                 int lastDot = expression.LastIndexOf('.');215 216                 string subExpression = expression;217                 string postExpression = string.Empty;218 219                 while (lastDot > -1) {220                     subExpression = expression.Substring(0, lastDot);221                     postExpression = expression.Substring(lastDot + 1);222                     yield return new ExpressionPair(subExpression, postExpression);223 224                     lastDot = subExpression.LastIndexOf('.');225                 }226             }227 228             private static object GetIndexedPropertyValue(object indexableObject, string key) {229                 Type indexableType = indexableObject.GetType();230 231                 ViewDataDictionary vdd = indexableObject as ViewDataDictionary;232                 if (vdd != null) {233                     return vdd[key];234                 }235 236                 MethodInfo containsKeyMethod = indexableType.GetMethod("ContainsKey", BindingFlags.Public | BindingFlags.Instance, null, new Type[] { typeof(string) }, null);237                 if (containsKeyMethod != null) {238                     if (!(bool)containsKeyMethod.Invoke(indexableObject, new object[] { key })) {239                         return null;240                     }241                 }242 243                 PropertyInfo info = indexableType.GetProperty("Item", BindingFlags.Public | BindingFlags.Instance, null, null, new Type[] { typeof(string) }, null);244                 if (info != null) {245                     return info.GetValue(indexableObject, new object[] { key });246                 }247 248                 PropertyInfo objectInfo = indexableType.GetProperty("Item", BindingFlags.Public | BindingFlags.Instance, null, null, new Type[] { typeof(object) }, null);249                 if (objectInfo != null) {250                     return objectInfo.GetValue(indexableObject, new object[] { key });251                 }252                 return null;253             }254 255             private static object GetPropertyValue(object container, string propertyName) {256                 // This method handles one "segment" of a complex property expression257 258                 // First, we try to evaluate the property based on its indexer259                 object value = GetIndexedPropertyValue(container, propertyName);260                 if (value != null) {261                     return value;262                 }263 264                 // If the indexer didn't return anything useful, continue265 266                 // If the container is a ViewDataDictionary then treat its Model property267                 // as the container instead of the ViewDataDictionary itself.268                 ViewDataDictionary vdd = container as ViewDataDictionary;269                 if (vdd != null) {270                     container = vdd.Model;271                 }272 273                 // Second, we try to use PropertyDescriptors and treat the expression as a property name274                 PropertyDescriptor descriptor = TypeDescriptor.GetProperties(container).Find(propertyName, true);275                 if (descriptor == null) {276                     return null;277                 }278 279                 return descriptor.GetValue(container);280             }281 282             private struct ExpressionPair {283                 public readonly string Left;284                 public readonly string Right;285 286                 public ExpressionPair(string left, string right) {287                     Left = left;288                     Right = right;289                 }290             }291         }292 293         #region IEnumerable Members294         [SuppressMessage("Microsoft.Security", "CA2123:OverrideLinkDemandsShouldBeIdenticalToBase")]295         IEnumerator IEnumerable.GetEnumerator() {296             return ((IEnumerable)_innerDictionary).GetEnumerator();297         }298         #endregion299 300     }

　　ViewData的用法如下:ViewData["user"] = LoginUser;  页面的代码<%=(ViewData["user"] as Users).UserName%>

　　ViewData的作用域从控制器设置值到页面值显示。

2.使用TempData

　　TempData同样属于ControllerBase 的属性 用法和ViewData 基本相同，但是他们的实质是不同的，ViewData 是数据字典类型而TempData是Session存储的值，TempData数据只能在控制器中传递一次，每个元素也只能被访问一次，然后Session中的值就会被自动删除，它的生命周期要比ViewData的要长.

　

3.使用Model

　　使用Model 顾名思义就是将一个实体对象绑定在页面上，上面两种都是放在作用域中。这里只讲用法。

　　public ActionResult Student()

　　{

　　　　DbContext context=new DbContext();

　　　　Student stu=context.Single(s=>s.ID==1);

　　　　return View(stu);

　　}

　　页面代码的使用：<%=(Model as MVCTest.Models.Student).Name %>  Model 是ViewPage d的一个属性值，用于　　　　     接收控制器中返回的值

　　Model 传输数据还可以这样用：

　　<%@ Page Language="C#" Inherits="System.Web.Mvc.ViewPage<MVCTest.Models.Student>" %>

　　<%=Model.Name %>

　　使用泛型的ViewPage，将Model中的值指定特定类型不用强制性转换

4.传递多个对象类型

　　其实传递多个对象类型，最简单的办法就是将这些对象封装成另外一个类的属性，然后将这个对象传递到页面。不在做介绍