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 must
161         // be aware of this and should plan accordingly. For example, the logic in SetModel() should be simple
162         // 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 names
209                 // given a complex expression. See the list above for an example of the result
210                 // 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 expression
257
258                 // First, we try to evaluate the property based on its indexer
259                 object value = GetIndexedPropertyValue(container, propertyName);
260                 if (value != null) {
261                     return value;
262                 }
263
264                 // If the indexer didn't return anything useful, continue

265
266                 // If the container is a ViewDataDictionary then treat its Model property
267                 // 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 name
274                 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 Members
294         [SuppressMessage("Microsoft.Security", "CA2123:OverrideLinkDemandsShouldBeIdenticalToBase")]
295         IEnumerator IEnumerable.GetEnumerator() {
296             return ((IEnumerable)_innerDictionary).GetEnumerator();
297         }
298         #endregion
299
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

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