asp.net-core-1.1 - 在 asp.net core 中合并 HtmlAttributes

Question

我在我的 asp.net mvc 5 编辑器模板中使用 Chris Pratt 的 MergeHtmlAttributes Html Helper Extension 方法有一段时间了。我开始将应用程序切换到 Asp.net core 1.1(.net framework 4.5.2)。 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;
    }
}

当我将类复制到上面时，它会标记语句:using System.Web.Mvc; - 无法解析符号 MVC。在删除该 using 语句后，我收到消息 cannot resolve symbol "HtmlHelper"in MergeHtmlAttributes(this HtmlHelper helper, ...)我可以选择添加 Microsoft.AspNetCore.Mvc.ViewFeatures.HtmlHelper或 .HtmlHelper<Tmodel>我选择了.HtmlHelper .之后它引用 RouteValueDictionary htmlAttributes = 行并表示它无法转换 IDictionary<string, object>至 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，我在我的一个编辑器模板中尝试使用 MergeHtmlAttributes 时都会收到以下错误。

'IHtmlHelper<object>'不包含“MergeHtmlAttributes”的定义和最佳扩展方法重载“HtmlHelperExtensions.MergeHtmlAttributes(HtmlHelper, object, object)”需要一个“HtmlHelper”类型的接收器

这一行抛出错误-> var htmlAttributes = Html.MergeHtmlAttributes(ViewData, defaultHtmlAttributesObject);

有没有办法让它在 asp.net core 中工作，或者是否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，是否有更新/更好的方法来使用标签助手来完成它？我真的很喜欢将 labelfor、txtboxfor、ValidationMessageFor 等全部放在一个 html 帮助程序中。

@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>

---

仅供引用。在转换为 asp.net core 1.1(和 .net framework 4.5.2)时，我最终将连接字符串放入它的 app.config 文件中，这允许 EF6 与 Asp.net core 一起工作，因此我可以继续使用我拥有的 EF 代码已构建，无论出于何种原因，它都不会在 appsettings.json 中找到连接字符串。

Answer 1

最初我没有意识到 Microsoft 现在使用 IHtmlHelper 而不是 HtmlHelper。

一旦我修改了代码以反射(reflect)该更改，并在 github 上找到了 Microsoft 的 mvc 存储库，这样我就能够找到他们对 AnonymousObjectToHtmlAttributes 的实现，它们都放在一起了。

下面的代码对我有用，但我可能不得不对我还没有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;
    }
}