在MVC 3中使用MVC 4擴展3

Question

我想使用Asp的Html.LabelFor()擴展名。 Net MVC 4將html屬性添加到Label。我正在使用MVC 3。我的問題是：我可以簡單升級我的​​dll？（這有什麼問題？...）或者它會在部署中出現問題？

Answer 1

這是MVC3源代碼

internal static MvcHtmlString LabelHelper(HtmlHelper html, ModelMetadata metadata, string htmlFieldName, string labelText = null) { 
string resolvedLabelText = labelText ?? metadata.DisplayName ?? metadata.PropertyName ?? htmlFieldName.Split('.').Last(); 
if (String.IsNullOrEmpty(resolvedLabelText)) { 
    return MvcHtmlString.Empty; 
} 

TagBuilder tag = new TagBuilder("label"); 
tag.Attributes.Add("for", TagBuilder.CreateSanitizedId(html.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldName(htmlFieldName))); 
tag.SetInnerText(resolvedLabelText); 
return tag.ToMvcHtmlString(TagRenderMode.Normal);} 

，這是mvc4

internal static MvcHtmlString LabelHelper(HtmlHelper html, ModelMetadata metadata, string htmlFieldName, string labelText = null, IDictionary<string, object> htmlAttributes = null){ 
string resolvedLabelText = labelText ?? metadata.DisplayName ?? metadata.PropertyName ?? htmlFieldName.Split('.').Last(); 
if (String.IsNullOrEmpty(resolvedLabelText)) 
{ 
    return MvcHtmlString.Empty; 
} 

TagBuilder tag = new TagBuilder("label"); 
tag.Attributes.Add("for", TagBuilder.CreateSanitizedId(html.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldName(htmlFieldName))); 
tag.SetInnerText(resolvedLabelText); 
tag.MergeAttributes(htmlAttributes, replaceExisting: true); 
return tag.ToMvcHtmlString(TagRenderMode.Normal);} 

只有一個行MVC3 InputExtensions.cs diffrenct tag.MergeAttributes(htmlAttributes, replaceExisting: true); 你可以找到TagBuilder.MergeAttributes函數用過的。
所以你可以自己寫一個擴展方法，而不需要升級你的項目。
下面是mvc4中的所有代碼，也許它會幫助你

// Copyright (c) Microsoft Corporation. All rights reserved. See License.txt in the project root for license information. 

using System.Collections.Generic; 
using System.Diagnostics.CodeAnalysis; 
using System.Linq; 
using System.Linq.Expressions; 

namespace System.Web.Mvc.Html 
{ 
    public static class LabelExtensions 
    { 
     public static MvcHtmlString Label(this HtmlHelper html, string expression) 
     { 
      return Label(html, 
         expression, 
         labelText: null); 
     } 

     public static MvcHtmlString Label(this HtmlHelper html, string expression, string labelText) 
     { 
      return Label(html, expression, labelText, htmlAttributes: null, metadataProvider: null); 
     } 

     public static MvcHtmlString Label(this HtmlHelper html, string expression, object htmlAttributes) 
     { 
      return Label(html, expression, labelText: null, htmlAttributes: htmlAttributes, metadataProvider: null); 
     } 

     public static MvcHtmlString Label(this HtmlHelper html, string expression, IDictionary<string, object> htmlAttributes) 
     { 
      return Label(html, expression, labelText: null, htmlAttributes: htmlAttributes, metadataProvider: null); 
     } 

     public static MvcHtmlString Label(this HtmlHelper html, string expression, string labelText, object htmlAttributes) 
     { 
      return Label(html, expression, labelText, htmlAttributes, metadataProvider: null); 
     } 

     public static MvcHtmlString Label(this HtmlHelper html, string expression, string labelText, IDictionary<string, object> htmlAttributes) 
     { 
      return Label(html, expression, labelText, htmlAttributes, metadataProvider: null); 
     } 

     internal static MvcHtmlString Label(this HtmlHelper html, string expression, string labelText, object htmlAttributes, ModelMetadataProvider metadataProvider) 
     { 
      return Label(html, 
         expression, 
         labelText, 
         HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes), 
         metadataProvider); 
     } 

     internal static MvcHtmlString Label(this HtmlHelper html, string expression, string labelText, IDictionary<string, object> htmlAttributes, ModelMetadataProvider metadataProvider) 
     { 
      return LabelHelper(html, 
           ModelMetadata.FromStringExpression(expression, html.ViewData, metadataProvider), 
           expression, 
           labelText, 
           htmlAttributes); 
     } 

     [SuppressMessage("Microsoft.Design", "CA1006:DoNotNestGenericTypesInMemberSignatures", Justification = "This is an appropriate nesting of generic types")] 
     public static MvcHtmlString LabelFor<TModel, TValue>(this HtmlHelper<TModel> html, Expression<Func<TModel, TValue>> expression) 
     { 
      return LabelFor<TModel, TValue>(html, expression, labelText: null); 
     } 

     [SuppressMessage("Microsoft.Design", "CA1006:DoNotNestGenericTypesInMemberSignatures", Justification = "This is an appropriate nesting of generic types")] 
     public static MvcHtmlString LabelFor<TModel, TValue>(this HtmlHelper<TModel> html, Expression<Func<TModel, TValue>> expression, string labelText) 
     { 
      return LabelFor(html, expression, labelText, htmlAttributes: null, metadataProvider: null); 
     } 

     [SuppressMessage("Microsoft.Design", "CA1006:DoNotNestGenericTypesInMemberSignatures", Justification = "This is an appropriate nesting of generic types")] 
     public static MvcHtmlString LabelFor<TModel, TValue>(this HtmlHelper<TModel> html, Expression<Func<TModel, TValue>> expression, object htmlAttributes) 
     { 
      return LabelFor(html, expression, labelText: null, htmlAttributes: htmlAttributes, metadataProvider: null); 
     } 

     [SuppressMessage("Microsoft.Design", "CA1006:DoNotNestGenericTypesInMemberSignatures", Justification = "This is an appropriate nesting of generic types")] 
     public static MvcHtmlString LabelFor<TModel, TValue>(this HtmlHelper<TModel> html, Expression<Func<TModel, TValue>> expression, IDictionary<string, object> htmlAttributes) 
     { 
      return LabelFor(html, expression, labelText: null, htmlAttributes: htmlAttributes, metadataProvider: null); 
     } 

     [SuppressMessage("Microsoft.Design", "CA1006:DoNotNestGenericTypesInMemberSignatures", Justification = "This is an appropriate nesting of generic types")] 
     public static MvcHtmlString LabelFor<TModel, TValue>(this HtmlHelper<TModel> html, Expression<Func<TModel, TValue>> expression, string labelText, object htmlAttributes) 
     { 
      return LabelFor(html, expression, labelText, htmlAttributes, metadataProvider: null); 
     } 

     [SuppressMessage("Microsoft.Design", "CA1006:DoNotNestGenericTypesInMemberSignatures", Justification = "This is an appropriate nesting of generic types")] 
     public static MvcHtmlString LabelFor<TModel, TValue>(this HtmlHelper<TModel> html, Expression<Func<TModel, TValue>> expression, string labelText, IDictionary<string, object> htmlAttributes) 
     { 
      return LabelFor(html, expression, labelText, htmlAttributes, metadataProvider: null); 
     } 

     internal static MvcHtmlString LabelFor<TModel, TValue>(this HtmlHelper<TModel> html, Expression<Func<TModel, TValue>> expression, string labelText, object htmlAttributes, ModelMetadataProvider metadataProvider) 
     { 
      return LabelFor(html, 
          expression, 
          labelText, 
          HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes), 
          metadataProvider); 
     } 

     internal static MvcHtmlString LabelFor<TModel, TValue>(this HtmlHelper<TModel> html, Expression<Func<TModel, TValue>> expression, string labelText, IDictionary<string, object> htmlAttributes, ModelMetadataProvider metadataProvider) 
     { 
      return LabelHelper(html, 
           ModelMetadata.FromLambdaExpression(expression, html.ViewData, metadataProvider), 
           ExpressionHelper.GetExpressionText(expression), 
           labelText, 
           htmlAttributes); 
     } 

     public static MvcHtmlString LabelForModel(this HtmlHelper html) 
     { 
      return LabelForModel(html, labelText: null); 
     } 

     public static MvcHtmlString LabelForModel(this HtmlHelper html, string labelText) 
     { 
      return LabelHelper(html, html.ViewData.ModelMetadata, String.Empty, labelText); 
     } 

     public static MvcHtmlString LabelForModel(this HtmlHelper html, object htmlAttributes) 
     { 
      return LabelHelper(html, html.ViewData.ModelMetadata, String.Empty, labelText: null, htmlAttributes: HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes)); 
     } 

     public static MvcHtmlString LabelForModel(this HtmlHelper html, IDictionary<string, object> htmlAttributes) 
     { 
      return LabelHelper(html, html.ViewData.ModelMetadata, String.Empty, labelText: null, htmlAttributes: htmlAttributes); 
     } 

     public static MvcHtmlString LabelForModel(this HtmlHelper html, string labelText, object htmlAttributes) 
     { 
      return LabelHelper(html, html.ViewData.ModelMetadata, String.Empty, labelText, HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes)); 
     } 

     public static MvcHtmlString LabelForModel(this HtmlHelper html, string labelText, IDictionary<string, object> htmlAttributes) 
     { 
      return LabelHelper(html, html.ViewData.ModelMetadata, String.Empty, labelText, htmlAttributes); 
     } 

     internal static MvcHtmlString LabelHelper(HtmlHelper html, ModelMetadata metadata, string htmlFieldName, string labelText = null, IDictionary<string, object> htmlAttributes = null) 
     { 
      string resolvedLabelText = labelText ?? metadata.DisplayName ?? metadata.PropertyName ?? htmlFieldName.Split('.').Last(); 
      if (String.IsNullOrEmpty(resolvedLabelText)) 
      { 
       return MvcHtmlString.Empty; 
      } 

      TagBuilder tag = new TagBuilder("label"); 
      tag.Attributes.Add("for", TagBuilder.CreateSanitizedId(html.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldName(htmlFieldName))); 
      tag.SetInnerText(resolvedLabelText); 
      tag.MergeAttributes(htmlAttributes, replaceExisting: true); 
      return tag.ToMvcHtmlString(TagRenderMode.Normal); 
     } 
    } 
}