.NET CORE MvcHtmlString(TextboxFor, LabelFor).ToString() 错误 [英] .NET CORE MvcHtmlString(TextboxFor, LabelFor).ToString() Error

问题描述

您好，我必须将 MvcHtmlString 转换为字符串.我之前用过这段代码.(.net framework)

Hello i must convert MvcHtmlString to string. I was using before this code.(.net framework)

TagBuilder div = new TagBuilder("div");
div.MergeAttribute("class", "form-group");
var label = helper.LabelFor(expression, new { @class = "control-label col-lg-1" });
div.InnerHtml += label.ToString();

现在我正在开发 .net 核心，但在

Now I am developing .net core and I get error at

div.InnerHtml += label.ToString();

错误图片

返回代表当前对象的字符串.对类型HtmlString"的引用声称它在System.Web"中定义，但无法找到.模块'System.Web, Version=4.0.0.0, Culture=neutral, PublicyToken=b03f5f7f11d50a3a 应该被引用

Returns a string that represent the current object. Reference to type 'HtmlString' claims it is defined in 'System.Web', but it could not be found. Module 'System.Web, Version=4.0.0.0, Culture=neutral, PublicyToken=b03f5f7f11d50a3a should be referenced

请帮帮我.我必须使用这种方法或替代方法.我正在尝试构建一个表单.

Please help me. I must use this method or alternative. I am trying build a form.

推荐答案

下面这行导致错误，因为 TagBuilder.InnerHtml 是只读属性，您不能使用 += 运算符来分配 HTML 字符串:

This line below causing error because TagBuilder.InnerHtml is a read only property and you can't use += operator to assign HTML string:

div.InnerHtml += label.ToString();

你应该做的是对现有的 LabelFor 助手使用 AppendHtml():

What you should do is using AppendHtml() against existing LabelFor helper:

div.InnerHtml.AppendHtml(label);

请注意，.NET Core MVC 不使用 System.Web 命名空间，而是使用 Microsoft.AspNetCore 父命名空间.您应该按照以下步骤尝试 IHtmlContent 来构建您自己的自定义助手而不是 MvcHtmlString:

Take note that .NET Core MVC doesn't use System.Web namespace, it uses Microsoft.AspNetCore parent namespace instead. You should try IHtmlContent to build your own custom helper instead of MvcHtmlString, by following these steps:

1) 包含下面提供的所有 using 语句以启用 IHtmlContent 和 IHtmlHelper 实例.

1) Include all using statements provided below to enable IHtmlContent and IHtmlHelper instance.

using Microsoft.AspNetCore.Html;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.AspNetCore.Mvc.ViewFeatures;

2) 使用 Microsoft.AspNetCore.Mvc.Rendering.IHtmlHelper 作为参数而不是 System.Web.Mvc.HtmlHelper 创建自定义助手，如下例所示:

2) Create your custom helper using Microsoft.AspNetCore.Mvc.Rendering.IHtmlHelper as parameter instead of System.Web.Mvc.HtmlHelper, shown in example below:

public static IHtmlContent CustomLabelFor<TModel, TProperty>(this IHtmlHelper<TModel> helper, Expression<Func<TModel, TProperty>> expression, object htmlAttributes)
{
    string result;

    TagBuilder div = new TagBuilder("div");
    div.MergeAttribute("class", "form-group");
    var label = helper.LabelFor(expression, new { @class = "control-label col-lg-1" });
    div.InnerHtml.AppendHtml(label);

    using (var sw = new System.IO.StringWriter())
    {
        div.WriteTo(sw, System.Text.Encodings.Web.HtmlEncoder.Default);
        result = sw.ToString();
    }

    return new HtmlString(result);
}

注意:此示例助手已在 VS 2017、.NET Core 2.1 中进行了测试.

Note: This example helper already tested in VS 2017, .NET Core 2.1.

相关问题:

在 ASP.Net Core 中创建自定义 HTML 助手

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