.NETMVC的自定义模型属性别名绑定的使用讲解

1、最近在研究 ASP.NET MVC 模型绑定，发现 DefaultModelBinder 有一个弊端，就是无法实现对浏览器请求参数的自定义，最初的想法是想为实体模型的属性设置特性（Attribute），然后通过取得设置的特性值对属性进行赋值，研究了好久 MVC 源码之后发现可以通过重写 DefaultModelBinder 的 BindProperty 方法可以达到预期的目的。ASP.NET MVC 中有一个自定义模型绑定特性 CustomModelBinderAttribute，打算通过重写 CustomModelBinderAtt

2、ribute 来对实体属性进行出来，实现如下：AttributeUsageAttribute(AttributeTargets.Class|AttributeTargets.Struct|AttributeTargets.Enum|AttributeTargets.Interface|AttributeTargets.Parameter, AllowMultiple = false,    Inherited = false)public abstract class CustomModelBinderAttribute : Attribute

3、但是由于 CustomModelBinderAttribute 不支持对属性设置特性，所以只好继承 Attribute 类重新写一个特性，代码如下：/ <summary>/ 表示一个调用自定义模型联编程序的特性。/ </summary>AttributeUsage(ValidTargets, AllowMultiple = false, Inherited = false)public class PropertyModelBinderAttribute : Attribute    / <summary

4、>    / 指定此属性可以应用特性的应用程序元素。    / </summary>    internal const AttributeTargets ValidTargets = AttributeTargets.Field | AttributeTargets.Enum | AttributeTargets.Property | AttributeTargets.Parameter;    / <summ

5、ary>    / 声明属性名称。    / </summary>    private string _propertyName = string.Empty;     / <summary>    / 获取或设置属性别名。    / </summary>    p

6、ublic string PropertyName            get return _propertyName;          / <summary>    / 使用指定的属性别名。    / </summary>    / &l

7、t;param name="propertyName">指定的属性别名。</param>    public PropertyModelBinderAttribute(string propertyName)            _propertyName = propertyName;         /

8、<summary>    / 检索关联的模型联编程序。    / </summary>    / <returns>对实现 System.Web.Mvc.IModelBinder 接口的对象的引用。</returns>    public IModelBinder GetBinder()        

9、0;   return new PropertyModelBinder();    这样就可以在实体模型的属性上设置别名了。/ <summary>/ 表示一个城市筛选实体对象模型。/ </summary>ModelBinder(typeof(PropertyModelBinder)public class CityFilteringModel : BaseEntityModel     / <summary>  

10、0; / 获取或设置城市英文名称。    / </summary>    public string CityEnglishName get; set;     / <summary>    / 获取或设置城市编号。    / </summary>    PropertyModelBinder("cid

11、")    public int CityId get; set;     / <summary>    / 获取或设置城市名称。    / </summary>    PropertyModelBinder("cname")    public string CityName get; set; 最后听

12、过重写 DefaultModelBinder 的 BindProperty 和 SetProperty 方法就可以对模型绑定的属性实现自定义了。/ <summary>/ 将浏览器请求映射到数据对象。/ </summary>public class PropertyModelBinder : DefaultModelBinder     / <summary>    / 初始化 <see cref="PropertyModel

13、Binder"/> 类的新实例。    / </summary>    public PropertyModelBinder()             / <summary>    / 使用指定的控制器上下文和绑定上下文来绑定模型。    / </summary

14、>    / <param name="controllerContext">运行控制器的上下文。</param>    / <param name="bindingContext">绑定模型的上下文。</param>    / <returns>已绑定的对象。</returns>    public override

15、object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)            var model = base.BindModel(controllerContext, bindingContext);        if (model is BaseEntiryModel)

16、 (BaseEntiryModel)model).BindModel(controllerContext, bindingContext);        return model;         / <summary>    /  使用指定的控制器上下文、绑定上下文、属性描述符和属性联编程序来返回属性值。    / <

17、;/summary>    / <param name="controllerContext">运行控制器的上下文。</param>    / <param name="bindingContext">绑定模型的上下文。</param>    / <param name="propertyDescriptor">要访问的属性的描述符。</para

18、m>    / <param name="propertyBinder">一个对象，提供用于绑定属性的方式。</param>    / <returns>一个对象，表示属性值。</returns>    protected override object GetPropertyValue(ControllerContext controllerContext, ModelBindingContext b

19、indingContext, System.ComponentModel.PropertyDescriptor propertyDescriptor, IModelBinder propertyBinder)            var value = base.GetPropertyValue(controllerContext, bindingContext, propertyDescriptor, propertyBinder);   &

20、#160;     return value;         / <summary>    / 使用指定的控制器上下文、绑定上下文和指定的属性描述符来绑定指定的属性。    / </summary>    / <param name="controllerContext">运行控制

21、器的上下文。</param>    / <param name="bindingContext">绑定模型的上下文。</param>    / <param name="propertyDescriptor">描述要绑定的属性。</param>    protected override void BindProperty(ControllerContext controlle

22、rContext, ModelBindingContext bindingContext, PropertyDescriptor propertyDescriptor)            string fullPropertyKey = CreateSubPropertyName(bindingContext.ModelName, propertyDescriptor.Name);       

23、0;object propertyValue = null;         if (propertyDescriptor.Attributestypeof(PropertyModelBinderAttribute) != null)                    var attribute = (P

24、ropertyModelBinderAttribute)propertyDescriptor.Attributestypeof(PropertyModelBinderAttribute);            string propertyName = attribute.PropertyName;            var valueResult =

25、 bindingContext.ValueProvider.GetValue(propertyName);             if (valueResult != null)                propertyValue = valueResult.AttemptedValue; 

26、               else                    if (!bindingContext.ValueProvider.ContainsPrefix(fullPropertyKey)   

27、60;                        return;                        &#

28、160;    / call into the property's model binder        IModelBinder propertyBinder = Binders.GetBinder(propertyDescriptor.PropertyType);        object originalPropertyValue = propertyDescriptor.Ge

29、tValue(bindingContext.Model);        ModelMetadata propertyMetadata = bindingContext.PropertyMetadatapropertyDescriptor.Name;        propertyMetadata.Model = originalPropertyValue;      

30、0; ModelBindingContext innerBindingContext = new ModelBindingContext()                    ModelMetadata = propertyMetadata,            

31、ModelName = fullPropertyKey,            ModelState = bindingContext.ModelState,            ValueProvider = bindingContext.ValueProvider       

32、60;        object newPropertyValue = GetPropertyValue(controllerContext, innerBindingContext, propertyDescriptor, propertyBinder);        if (newPropertyValue = null)         

33、           newPropertyValue = propertyValue;                 propertyMetadata.Model = newPropertyValue;        / validat

34、ion        ModelState modelState = bindingContext.ModelStatefullPropertyKey;         if (modelState = null | modelState.Errors.Count = 0)             

35、       if (OnPropertyValidating(controllerContext, bindingContext, propertyDescriptor, newPropertyValue)                           

36、; SetProperty(controllerContext, bindingContext, propertyDescriptor, newPropertyValue);                OnPropertyValidated(controllerContext, bindingContext, propertyDescriptor, newPropertyValue);   &

37、#160;                        else                    SetProperty(controllerConte

38、xt, bindingContext, propertyDescriptor, newPropertyValue);             / Convert FormatExceptions (type conversion failures) into InvalidValue messages            foreach (Mod

39、elError error in modelState.Errors.Where(err => String.IsNullOrEmpty(err.ErrorMessage) && err.Exception != null).ToList()                            

40、for (Exception exception = error.Exception; exception != null; exception = exception.InnerException)                                 &#

41、160;  / We only consider "known" type of exception and do not make too aggressive changes here                    if (exception is FormatException | exception is OverflowException)

42、                                            string displayName = propertyMetadat

43、a.GetDisplayName();                        string errorMessageTemplate = GetValueInvalidResource(controllerContext);          

44、0;             string errorMessage = String.Format(CultureInfo.CurrentCulture, errorMessageTemplate, modelState.Value.AttemptedValue, displayName);              

45、0;         modelState.Errors.Remove(error);                        modelState.Errors.Add(errorMessage);     &#

46、160;                  break;                              &#

47、160;                                 /base.BindProperty(controllerContext, bindingContext, propertyDescriptor);    

48、     / <summary>    / 使用指定的控制器上下文、绑定上下文和属性值来设置指定的属性。    / </summary>    / <param name="controllerContext">运行控制器的上下文。</param>    / <param name="bindingCon

49、text">绑定模型的上下文。</param>    / <param name="propertyDescriptor">描述要绑定的属性。</param>    / <param name="value">为属性设置的值。</param>    protected override void SetProperty(ControllerContext con

50、trollerContext, ModelBindingContext bindingContext, PropertyDescriptor propertyDescriptor, object value)            ModelMetadata propertyMetadata = bindingContext.PropertyMetadatapropertyDescriptor.Name;      

51、  propertyMetadata.Model = value;        string modelStateKey = CreateSubPropertyName(bindingContext.ModelName, propertyMetadata.PropertyName);         if (value = null && bindingContext.ModelState

52、.IsValidField(modelStateKey)                    ModelValidator requiredValidator = ModelValidatorProviders.Providers.GetValidators(propertyMetadata, controllerContext).Where(v => v.IsRequired).Firs

53、tOrDefault();            if (requiredValidator != null)                            foreach (ModelVal

54、idationResult validationResult in requiredValidator.Validate(bindingContext.Model)                                    bi

55、ndingContext.ModelState.AddModelError(modelStateKey, validationResult.Message);                                     

56、;        bool isNullValueOnNonNullableType = value = null && !TypeAllowsNullValue(propertyDescriptor.PropertyType);         if (!propertyDescriptor.IsReadOnly && !isNullValueOnNonNullableType) &

57、#160;                  try                            var typeValue =

58、Convert.ChangeType(value, propertyDescriptor.PropertyType, CultureInfo.InvariantCulture);                propertyDescriptor.SetValue(bindingContext.Model, typeValue);         

59、               catch (Exception ex)                            if (bindingContext.Mod

60、elState.IsValidField(modelStateKey)                                    bindingContext.ModelState.AddModelError(modelStat

61、eKey, ex);                                             if (isNullValueOnNon

62、NullableType && bindingContext.ModelState.IsValidField(modelStateKey)                    bindingContext.ModelState.AddModelError(modelStateKey, GetValueRequiredResource(controllerContext);

63、0;                  / <summary>    / 使用指定的控制器上下文和绑定上下文来返回模型的属性。    / </summary>    / <param name="controllerContext">运行控制器

64、的上下文。</param>    / <param name="bindingContext">绑定模型的上下文。</param>    / <returns>属性描述符的集合。</returns>    protected override PropertyDescriptorCollection GetModelProperties(ControllerContext controllerCo

65、ntext, ModelBindingContext bindingContext)            bindingContext.PropertyFilter = new Predicate<string>(pred);        var values = base.GetModelProperties(controllerContext, bindingContext);

66、        return values;         / <summary>    / 获取属性筛选器的判定对象。    / </summary>    / <param name="target">属性筛选器的属性。</param>

67、    / <returns>一个布尔值。</returns>    protected bool pred(string target)            return true;         #region Private .    

68、 / <summary>    / 类型允许空值。    / </summary>    / <param name="type">指定的类型。</param>    / <returns>若类型值为空，则返回 true，否则返回 false。</returns>    private stati

69、c bool TypeAllowsNullValue(Type type)            return (!type.IsValueType | IsNullableValueType(type);         / <summary>    / 是可为空值类型。    / </s

70、ummary>    / <param name="type">指定的类型。</param>    / <returns>若类型值为空，则返回 true，否则返回 false。</returns>    private static bool IsNullableValueType(Type type)