我已经在我的asp.net mvc 5编辑器模板中使用了Chris Pratt的MergeHtmlAttributes Html Helper Extension方法一段时间了。我开始将应用程序切换到Asp.net核心1.1（.net framework 4.5.2）。并且htmlhelperExtension对我不起作用。
public static partial class HtmlHelperExtensions
{
//https://cpratt.co/html-editorfor-and-htmlattributes/
public static IDictionary<string, object> MergeHtmlAttributes(this HtmlHelper helper, object htmlAttributesObject, object defaultHtmlAttributesObject)
{
var concatKeys = new string[] { "class" };
var htmlAttributesDict = htmlAttributesObject as IDictionary<string, object>;
var defaultHtmlAttributesDict = defaultHtmlAttributesObject as IDictionary<string, object>;
RouteValueDictionary htmlAttributes = (htmlAttributesDict != null)
? new RouteValueDictionary(htmlAttributesDict)
: HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributesObject);
RouteValueDictionary defaultHtmlAttributes = (defaultHtmlAttributesDict != null)
? new RouteValueDictionary(defaultHtmlAttributesDict)
: HtmlHelper.AnonymousObjectToHtmlAttributes(defaultHtmlAttributesObject);
foreach (var item in htmlAttributes)
{
if (concatKeys.Contains(item.Key))
{
defaultHtmlAttributes[item.Key] = (defaultHtmlAttributes[item.Key] != null)
? string.Format("{0} {1}", defaultHtmlAttributes[item.Key], item.Value)
: item.Value;
}
else
{
if(item.Key?.ToString() == "divClass")
{
continue;
}
defaultHtmlAttributes[item.Key] = item.Value;
}
}
return defaultHtmlAttributes;
}
}
当我复制该类时，标记该语句：using System.Web.Mvc; - 不解析符号MVC。
删除使用语句后，我得到的消息无法解析符号＆＃34; HtmlHelper＆＃34;在MergeHtmlAttributes(this HtmlHelper helper, ...)
我可以选择添加其中一个
Microsoft.AspNetCore.Mvc.ViewFeatures.HtmlHelper或.HtmlHelper<Tmodel>我选择了.HtmlHelper。
之后它引用了RouteValueDictionary行htmlAttributes =并表示它无法将IDictionary<string, object>转换为system.web.Routing.RouteValueDictionary。我应该将类型更改为IDictionary<string, object>或转换为RouteValueDictionary。无论哪种方式，当我尝试在我的一个编辑器模板中使用MergeHtmlAttributes时，我都会收到以下错误。
'IHtmlHelper<object>'不包含＆＃39; MergeHtmlAttributes＆＃39;的定义。和最好的扩展方法重载＆＃39; HtmlHelperExtensions.MergeHtmlAttributes（HtmlHelper，object，object）＆＃39;需要一个类型为＆＃39; HtmlHelper＆＃39;
此行正在抛出错误 - ＆gt; var htmlAttributes = Html.MergeHtmlAttributes(ViewData, defaultHtmlAttributesObject);
有没有办法让它在asp.net核心中运行，还是有不同的方法来实现相同的结果？这是我的一个编辑器模板的示例，因此您可以看到正在使用的MergeHtmlAttributes。如果我不能再像这样构建模板，那么有更新/更好的方法来使用标记助手吗？我真的很喜欢在一个html助手中使用labelfor，txtboxfor，ValidationMessageFor等。
@model int?
@{
var defaultHtmlAttributesObject = new { @class = "form-control" };
var htmlAttributes = Html.MergeHtmlAttributes(ViewData, defaultHtmlAttributesObject);
object divClass;
ViewData.TryGetValue("divClass", out divClass);
if (divClass == null) { divClass = ""; }
IDictionary<string, object> validationAttributes = Html.GetUnobtrusiveValidationAttributes("");
Html.ViewContext.FormContext.RenderedField(ViewData.TemplateInfo.GetFullHtmlFieldName(null), false);
}
<div class="form-group @divClass @(Html.ValidationErrorFor(x => x, " has-error"))">
@Html.LabelFor(x => x, new { @class = "control-label" })
@if (validationAttributes.ContainsKey("data-val-required"))
{<span class="text-danger">*</span>}
@Html.TextBoxFor(x => x, htmlAttributes)
@Html.ValidationMessageFor(model => model, "", new { @class = "text-danger" })
</div>
F.Y.I。转换到asp.net核心1.1（和.net框架4.5.2）时，我最终将连接字符串放在它的app.config文件中，该文件允许EF6与Asp.net核心一起工作，这样我就可以继续使用我构建的EF代码，无论出于何种原因，它都无法在appsettings.json中找到连接字符串。
答案 0 :(得分：3)
最初我没有意识到微软现在使用 IHtmlHelper而不是HtmlHelper 。
一旦我修改了代码以反映该更改并在github 上找到 Microsoft的mvc存储库，以便我能够找到它们的AnonymousObjectToHtmlAttributes的实现，它们就全部落在了一起。
以下代码对我有用，但我可能不得不对我尚未想到的边缘情况进行一些更改。
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web.Routing;
using Microsoft.AspNetCore.Mvc.Rendering;
public static class HtmlHelperExtensions
{
//http://cpratt.co/html-editorfor-and-htmlattributes/
/// <summary>
/// This is used with the EditorTemplates to copy the page element's htmlAttributes over to the editorTemplates
/// while still being able to specify values to always use (like @class = "form-control") in the editorTemplates.
/// </summary>
public static IDictionary<string, object> MergeHtmlAttributes(this IHtmlHelper helper, object htmlAttributesObject, object defaultHtmlAttributesObject)
{
var concatKeys = new[] { "class" };
var htmlAttributesDict = htmlAttributesObject as IDictionary<string, object>;
var defaultHtmlAttributesDict = defaultHtmlAttributesObject as IDictionary<string, object>;
RouteValueDictionary htmlAttributes = new RouteValueDictionary(htmlAttributesDict != null
? htmlAttributesDict
: AnonymousObjectToHtmlAttributes(htmlAttributesObject));
RouteValueDictionary defaultHtmlAttributes = new RouteValueDictionary(defaultHtmlAttributesDict != null
? defaultHtmlAttributesDict
: AnonymousObjectToHtmlAttributes(defaultHtmlAttributesObject));
foreach (var item in htmlAttributes)
{
if (concatKeys.Contains(item.Key))
{
defaultHtmlAttributes[item.Key] = defaultHtmlAttributes[item.Key] != null
? string.Format("{0} {1}", defaultHtmlAttributes[item.Key], item.Value)
: item.Value;
}
else
{
if(item.Key == "divClass")
{
continue;
}
defaultHtmlAttributes[item.Key] = item.Value;
}
}
return defaultHtmlAttributes;
}
private static IDictionary<string, object> AnonymousObjectToHtmlAttributes(object htmlAttributes)
{
var dictionary = htmlAttributes as IDictionary<string, object>;
if (dictionary != null)
{
return new Dictionary<string, object>(dictionary, StringComparer.OrdinalIgnoreCase);
}
dictionary = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
if (htmlAttributes != null)
{
var stringAttributes = htmlAttributes.ToString();
stringAttributes = stringAttributes.Replace("{", "").Replace("}", "");
string[] attributesArray = stringAttributes.Split(new[] { ','}, StringSplitOptions.RemoveEmptyEntries);
foreach (var helper in attributesArray)
{
string[] attribKeyValue = helper.Trim().Split(' ');
dictionary[attribKeyValue.First()] = attribKeyValue.Last();
}
}
return dictionary;
}
}