asp.net mvc 2 简简单单做开发 自定义DropdownList控件

　　asp.net mvc 2 给我们提供了强大的自定义功能，今天主要说下DropdownList自定义绑定字段显示，通过ViewData设定DropdownList的数据项。自动绑定显示。实现的方式。在global.asax 中注册 FieldTemplateMetadataProvider，

 ModelMetadataProviders.Current = new mvc.Models.FieldTemplateMetadataProvider();
通过返回的 FieldTemplateMetadata 。在MetaData中指定使用DropDownList的字段
       [Display( Name="",Order=12)]
        [Required]
        [SearchFilter]
        [DisplayName("栏目")]
        [DropDownList("Category", "Id", "Name")]
        public int Cid { get; set; }

通过DropDownList指定调用的模板为dropdownlist.ascx ,在dropdownlist.ascx 将默认的 ModelMetadata 转成FieldTemplateMetadata 获取 DropDownListAttribute 。

<script runat="server">
    DropDownListAttribute GetDropDownListAttribute()
    {
        FieldTemplateMetadata metaData = ViewData.ModelMetadata as FieldTemplateMetadata;
 
        return (metaData != null) ? metaData.Attributes.OfType<DropDownListAttribute>().SingleOrDefault() : null;
    }
</script>

 
　　通过DropDownListAttribute 获得 ViewData的key ，绑定的文本对应的字段，值对应的字段，使用html.DropDownlist显示数据

    DropdownList.ascx 代码

代码

<% @ Import Namespace = " mvc.Models " %>
<% @ Control Language = " C# "  Inherits = " System.Web.Mvc.ViewUserControl "   %>
< script runat = " server " >
    DropDownListAttribute GetDropDownListAttribute()
    {
        FieldTemplateMetadata metaData  =  ViewData.ModelMetadata  as  FieldTemplateMetadata;

         return  (metaData  !=   null )  ?  metaData.Attributes.OfType < DropDownListAttribute > ().SingleOrDefault() :  null ;
    }
</ script >
<%  DropDownListAttribute attribute  =  GetDropDownListAttribute(); %>
<%   if  (attribute  !=   null ) { %>
     <%=  Html.DropDownList( string .Empty,  new  SelectList(ViewData[attribute.ViewDataKey]  as  IEnumerable, attribute.DataValueField, attribute.DataTextField, Model), attribute.OptionLabel, attribute.HtmlAttributes)  %>
<%  } %>
<%   else  { %>
     <%=  Html.DisplayForModel()  %>
<%  } %>

 

自定义DropDownListAttribute 属性

 

代码

namespace  mvc.Models
{
     using  System;
     using  System.Collections.Generic;
     using  System.ComponentModel;
     using  System.ComponentModel.DataAnnotations;
     using  System.Linq;
     using  System.Web.Routing;

    [AttributeUsage(AttributeTargets.Property, AllowMultiple  =   false , Inherited  =   true )]
     public   sealed   class  DropDownListAttribute : Attribute, ITemplateField
    {
         private   static   string  defaultTemplateName;

         public  DropDownListAttribute( string  viewDataKey,  string  dataValueField) :  this (viewDataKey, dataValueField,  null )
        {
        }

         public  DropDownListAttribute( string  viewDataKey,  string  dataValueField,  string  dataTextField) :  this (viewDataKey, dataValueField, dataTextField,  null )
        {
        }

         public  DropDownListAttribute( string  viewDataKey,  string  dataValueField,  string  dataTextField,  string  optionLabel) :  this (DefaultTemplateName, viewDataKey, dataValueField, dataTextField, optionLabel,  null )
        {
        }

         public  DropDownListAttribute( string  viewDataKey,  string  dataValueField,  string  dataTextField,  string  optionLabel,  object  htmlAttributes) :  this (DefaultTemplateName, viewDataKey, dataValueField, dataTextField, optionLabel, htmlAttributes)
        {
        }

         public  DropDownListAttribute( string  templateName,  string  viewDataKey,  string  dataValueField,  string  dataTextField,  string  optionLabel,  object  htmlAttributes)
        {
             if  ( string .IsNullOrEmpty(templateName))
            {
                 throw   new  ArgumentException( " Template name cannot be empty. " );
            }

             if  ( string .IsNullOrEmpty(viewDataKey))
            {
                 throw   new  ArgumentException( " View data key cannot be empty. " );
            }

             if  ( string .IsNullOrEmpty(dataValueField))
            {
                 throw   new  ArgumentException( " Data value field cannot be empty. " );
            }

            TemplateName  =  templateName;
            ViewDataKey  =  viewDataKey;
            DataValueField  =  dataValueField;
            DataTextField  =  dataTextField;
            OptionLabel  =  optionLabel;
            HtmlAttributes  =   new  RouteValueDictionary(htmlAttributes);
        }

         public   static   string  DefaultTemplateName
        {
             get
            {
                 if  ( string .IsNullOrEmpty(defaultTemplateName))
                {
                    defaultTemplateName  =   " DropDownList " ;
                }

                 return  defaultTemplateName;
            }
             set
            {
                defaultTemplateName  =  value;
            }
        }

         public   string  TemplateName {  get ;  private   set ; }

         public   string  ViewDataKey {  get ;  private   set ; }

         public   string  DataValueField {  get ;  private   set ; }

         public   string  DataTextField {  get ;  private   set ; }

         public   string  OptionLabel {  get ;  private   set ; }

         public  IDictionary < string ,  object >  HtmlAttributes {  get ;  private   set ; }

         public   object  GetSelectedValue( object  model)
        {
             return  GetPropertyValue(model, DataValueField);
        }

         public   object  GetSelectedText( object  model)
        {
             return  GetPropertyValue(model,  ! string .IsNullOrEmpty(DataTextField)  ?  DataTextField : DataValueField);
        }

         private   static   object  GetPropertyValue( object  model,  string  propertyName)
        {
             if  (model  !=   null )
            {
                PropertyDescriptor property  =  GetTypeDescriptor(model.GetType()).GetProperties()
                                                                                .Cast < PropertyDescriptor > ()
                                                                                .SingleOrDefault(p  =>   string .Compare(p.Name, propertyName, StringComparison.OrdinalIgnoreCase)  ==   0 );
               
                 if  (property  !=   null )
                {
                     return  property.GetValue(model);
                }
            }

             return   null ;
        }

         private   static  ICustomTypeDescriptor GetTypeDescriptor(Type type)
        {
             return   new  AssociatedMetadataTypeTypeDescriptionProvider(type).GetTypeDescriptor(type);
        }
    }
}

 

自定义DataAnnotationsModelMetadata

 

代码

public   class  FieldTemplateMetadata : DataAnnotationsModelMetadata
    {
         public  FieldTemplateMetadata(DisplayAttribute aa, DataAnnotationsModelMetadataProvider provider, Type containerType, Func < object >  modelAccessor, Type modelType,  string  propertyName, DisplayColumnAttribute displayColumnAttribute, IEnumerable < Attribute >  attributes) :  base (provider, containerType, modelAccessor, modelType, propertyName, displayColumnAttribute)
        {
            Attributes  =   new  List < Attribute > (attributes);
            Display  =  aa;
        }

         public  IList < Attribute >  Attributes
        {
             get ;
             private   set ;
        }
         public  DisplayAttribute Display {  get ;  set ; }
    }

 

自定义 DataAnnotationsModelMetadataProvider

 

代码

public   class  FieldTemplateMetadataProvider : DataAnnotationsModelMetadataProvider
    {
         protected   override  ModelMetadata CreateMetadata(IEnumerable < Attribute >  attributes, Type containerType, Func < object >  modelAccessor, Type modelType,  string  propertyName)
        {
            DataAnnotationsModelMetadata result  =  (DataAnnotationsModelMetadata)  base .CreateMetadata(attributes, containerType, modelAccessor, modelType, propertyName);

             string  templateName  =  attributes.OfType < ITemplateField > ()
                                            .Select(field  =>  field.TemplateName)
                                            .LastOrDefault();
            List < System.Attribute >  attributeList  =   new  List < System.Attribute > (attributes);
            DisplayAttribute disp  =  attributeList.OfType < DisplayAttribute > ().FirstOrDefault();
             if  (disp  !=   null )
            {
                result.ShortDisplayName  =  disp.Order.ToString(); ;
                result.Description  =  disp.Description;
            }

           

            var data =  ( new  FieldTemplateMetadata(disp,  this , containerType, modelAccessor, modelType, propertyName, attributes.OfType < DisplayColumnAttribute > ().FirstOrDefault(), attributes)

                    {
                        TemplateHint  =   ! string .IsNullOrEmpty(templateName)  ?  templateName : result.TemplateHint,
                        HideSurroundingHtml  =  result.HideSurroundingHtml,
                        DataTypeName  =  result.DataTypeName,
                        IsReadOnly  =  result.IsReadOnly,
                        NullDisplayText  =  result.NullDisplayText,
                        DisplayFormatString  =  result.DisplayFormatString,
                        ConvertEmptyStringToNull  =  result.ConvertEmptyStringToNull,
                        EditFormatString  =  result.EditFormatString,
                        ShowForDisplay  =  result.ShowForDisplay,
                        ShowForEdit  =  result.ShowForEdit,
                        DisplayName  =  result.DisplayName,
                        Description  =  result.Description,
                        ShortDisplayName  =  result.ShortDisplayName,

                    });

            SearchFilterAttribute searchFilterAttribute  =  attributes.OfType < SearchFilterAttribute > ().FirstOrDefault();
             if  (searchFilterAttribute  !=   null )
            {
                data.AdditionalValues.Add( " Search " , searchFilterAttribute);
            }

            OrderByAttribute orderByAttribute  =  attributes.OfType < OrderByAttribute > ().FirstOrDefault();
             if  (orderByAttribute  !=   null )
            {
                data.AdditionalValues.Add( " OrderBy " , orderByAttribute);
            }
             return  data;
        }
    }