DisplayAttribute.Description atribut qiymatini qanday aks ettiraman?

Men shunday yordamchi bilan yakunlandim:

using System;
using System.Linq.Expressions;
using System.Web.Mvc;

public static class MvcHtmlHelpers
{
    public static MvcHtmlString DescriptionFor<TModel, TValue>(this HtmlHelper<TModel> self, Expression<Func<TModel, TValue>> expression)
    {
        var metadata = ModelMetadata.FromLambdaExpression(expression, self.ViewData);
        var description = metadata.Description;

        return MvcHtmlString.Create(string.Format(@"<span>{0}</span>", description));
    }
}

Meni to'g'ri yo'lga boshlaganlarga rahmat. :)

Ushbu maqoladagi texnikadan foydalanish haqida Shaklingizdagi maydonlar uchun vizual maslahatlarni ko‘rsatish, siz qiymatga quyidagilar orqali kirishingiz mumkin:

@Html.TextBoxFor( 
        model => model.Email , 
        new { title = ModelMetadata.FromLambdaExpression<RegisterModel , string>( 
            model => model.Email , ViewData ).Description } )  

Men qabul qilingan javobni ishlatmoqchi edim, lekin u ASP.NET Core 1/2 (aka MVC) uchun ishlamadi. 6) chunki ModelMetadata.FromLambdaExpression endi mavjud emas va ExpressionMetadataProvider ga ko'chirildi (shuningdek, foydalanish biroz o'zgartirildi).

Bu ASP.NET Core 1.1 va 2 bilan ishlatishingiz mumkin boʻlgan yangilangan kengaytma usuli:

using System;
using System.Linq.Expressions;
using Microsoft.AspNetCore.Html;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.AspNetCore.Mvc.ViewFeatures.Internal;

public static class HtmlExtensions
{
    public static IHtmlContent DescriptionFor<TModel, TValue>(this IHtmlHelper<TModel> html, Expression<Func<TModel, TValue>> expression)
    {
        if (html == null) throw new ArgumentNullException(nameof(html));
        if (expression == null) throw new ArgumentNullException(nameof(expression));

        var modelExplorer = ExpressionMetadataProvider.FromLambdaExpression(expression, html.ViewData, html.MetadataProvider);
        if (modelExplorer == null) throw new InvalidOperationException($"Failed to get model explorer for {ExpressionHelper.GetExpressionText(expression)}");

        return new HtmlString(modelExplorer.Metadata.Description);
    }
}

ASP.NET Core 1

ASP.NET Core 1 uchun bir xil kod ishlaydi, lekin sizga usings boshqa nom maydoni kerak bo'ladi:

using System;
using System.Linq.Expressions;
using Microsoft.AspNet.Html.Abstractions;
using Microsoft.AspNet.Mvc.ViewFeatures;

Foydalanish

@Html.DescriptionFor(model => model.Phone1)

ASP.NET MVC Core-da siz HTML-ni o'xshash qilib ko'rsatadigan yangi teg yordamchilaridan foydalanishingiz mumkin... HTML :)

Shunga o'xshash:

<div class="form-group row">
    <label asp-for="Name" class="col-md-2 form-control-label"></label>
    <div class="col-md-10">
        <input asp-for="Name" class="form-control" aria-describedby="Name-description" />
        <span asp-description-for="Name" class="form-text text-muted" />
        <span asp-validation-for="Name" class="text-danger" />
    </div>
</div>

Eslatma 1: Kirish elementida aria-describedby atributidan foydalanishingiz mumkin, chunki bu id avtomatik ravishda asp-description-for atributli span elementida yaratiladi.

Eslatma 2: Bootstrap 4 da form-text va text-muted sinflari blok darajasidagi yordam matni uchun v3 help-block sinfini almashtiradi.

Ushbu sehr sodir bo'lishi uchun siz shunchaki yangi teg yordamchisini yaratishingiz kerak:

using System;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.AspNetCore.Mvc.ViewFeatures;
using Microsoft.AspNetCore.Razor.TagHelpers;

/// <summary>
/// <see cref="ITagHelper"/> implementation targeting &lt;span&gt; elements with an <c>asp-description-for</c> attribute.
/// Adds an <c>id</c> attribute and sets the content of the &lt;span&gt; with the Description property from the model data annotation DisplayAttribute.
/// </summary>
[HtmlTargetElement("span", Attributes = DescriptionForAttributeName)]
public class SpanDescriptionTagHelper : TagHelper
{
    private const string DescriptionForAttributeName = "asp-description-for";

    /// <summary>
    /// Creates a new <see cref="SpanDescriptionTagHelper"/>.
    /// </summary>
    /// <param name="generator">The <see cref="IHtmlGenerator"/>.</param>
    public SpanDescriptionTagHelper(IHtmlGenerator generator)
    {
        Generator = generator;
    }

    /// <inheritdoc />
    public override int Order
    {
        get
        {
            return -1000;
        }
    }

    [HtmlAttributeNotBound]
    [ViewContext]
    public ViewContext ViewContext { get; set; }

    protected IHtmlGenerator Generator { get; }

    /// <summary>
    /// An expression to be evaluated against the current model.
    /// </summary>
    [HtmlAttributeName(DescriptionForAttributeName)]
    public ModelExpression DescriptionFor { get; set; }

    /// <inheritdoc />
    /// <remarks>Does nothing if <see cref="DescriptionFor"/> is <c>null</c>.</remarks>
    public override async Task ProcessAsync(TagHelperContext context, TagHelperOutput output)
    {
        if (context == null)
        {
            throw new ArgumentNullException(nameof(context));
        }

        if (output == null)
        {
            throw new ArgumentNullException(nameof(output));
        }

        var metadata = DescriptionFor.Metadata;

        if (metadata == null)
        {
            throw new InvalidOperationException(string.Format("No provided metadata ({0})", DescriptionForAttributeName));
        }

        output.Attributes.SetAttribute("id", metadata.PropertyName + "-description");

        if( !string.IsNullOrWhiteSpace( metadata.Description))
        {
            output.Content.SetContent(metadata.Description);
            output.TagMode = TagMode.StartTagAndEndTag;
        }
    }
}

Teg yordamchilaringizni barcha Razor ko'rinishlarimiz uchun mavjud qiling. addTagHelper direktivasini Views/_ViewImports.cshtml fayliga qo'shing:

@addTagHelper "*, YourAssemblyName"

Eslatma 1: YourAssemblyName ni loyihangizning yig'ish nomi bilan almashtiring.

Eslatma 2: Buni barcha teg yordamchilaringiz uchun bir marta qilish kifoya!

Tag Helpers haqida batafsil maʼlumotni bu yerda: https://docs.asp.net/en/latest/mvc/views/tag-helpers/intro.html

Bo'ldi shu! Yangi teg yordamchilari bilan zavqlaning!

Agar kimdir qabul qilingan javobdan qanday foydalanishni bilmoqchi bo'lsa

1- Yechim tadqiqotchisida > Yangi jild qo‘shing > uni “Yordamchilar” deb nomlang, masalan,
2- Yangi sinf qo‘shing, uni “CustomHtmlHelpers” deb nomlang, masalan
3- Kodni joylashtiring:

public static class MvcHtmlHelpers
{
    public static string DescriptionFor<TModel, TValue>(this HtmlHelper<TModel> self, Expression<Func<TModel, TValue>> expression)
    {
        var metadata = ModelMetadata.FromLambdaExpression(expression, self.ViewData);
        var description = metadata.Description;

        return string.IsNullOrWhiteSpace(description) ? "" : description;
    }
}

4- Sizning modelingizda yoki viewModel-da undan foydalanib:

[Display(Name = "User Name", Description = "Enter your User Name")]
public string FullName { get; set; }

5- Razor ko'rinishida @modeldan keyin ushbu qatorni kiriting

@using YOUR_PROJECT.Helpers 

6- Ta'rifni quyidagicha ko'rsating:

@Html.DescriptionFor(m => m.FullName) 

7- Matnni kiritish to'ldiruvchisida ko'rsatish uchun tavsifdan foydalanishni xohlashingiz mumkin:

@Html.DisplayNameFor(m => m.FullName)
@Html.TextBoxFor(m => m.FullName, new { @class = "form-control", placeholder = Html.DescriptionFor(m => m.FullName) })

rahmat

@ViewData.ModelMetadata.Properties
   .Where(m => m.PropertyName == "Phone1").FirstOrDefault().Description

Shunday qilib, agar siz bootstrap dan foydalansangiz, shunga o'xshash narsa

<div class="form-group col-sm-6">
   @Html.LabelFor(m => m.Organization.Phone1)
   @Html.EditorFor(m => m.Organization.Phone1)
   <p class="help-block">
      @ViewData.ModelMetadata.Properties
         .Where(m => m.PropertyName == "DayCount").FirstOrDefault().Description
   </p>
</div>

Mana ASP.NET Core 3.1 va 5 uchun yangilangan versiya:

public static class HtmlExtensions
{
    public static IHtmlContent DescriptionFor<TModel, TValue>(this IHtmlHelper<TModel> html, Expression<Func<TModel, TValue>> expression)
    {
        if (html == null) throw new ArgumentNullException(nameof(html));
        if (expression == null) throw new ArgumentNullException(nameof(expression));

        var expressionProvider = html.ViewContext?.HttpContext?.RequestServices?.GetService<ModelExpressionProvider>()
            ?? new ModelExpressionProvider(html.MetadataProvider);
        var modelExpression = expressionProvider.CreateModelExpression(html.ViewData, expression);

        return new HtmlString(modelExpression.Metadata.Description);
    }
}

Biz ModelExpressionProvider orqali o'tishimiz kerak, chunki ExpressionMetadataProvider ichki belgilandi.

ModelExpressionProvider.CreateModelExpression() baribir ExpressionMetadataProvider.FromLambdaExpression() ga ichki qo'ng'iroq qiladi:

Tavsif atributi qiymatini berish uchun modelingizga mos keladigan maxsus yordamchi yozishingiz kerak bo'ladi.

...va agar siz tavsifni forma yorlig'ida asboblar maslahati sifatida olishni istasangiz, quyidagi kabi teg yordamchisini qo'shing:

using System;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.AspNetCore.Mvc.ViewFeatures;
using Microsoft.AspNetCore.Razor.TagHelpers;

/// <summary>
/// <see cref="ITagHelper"/> implementation targeting &lt;label&gt; elements with an <c>asp-for</c> attribute.
/// Adds a <c>title</c> attribute to the &lt;label&gt; with the Description property from the model data annotation DisplayAttribute.
/// </summary>
[HtmlTargetElement("label", Attributes = ForAttributeName)]
public class LabelTitleTagHelper : TagHelper
{
    private const string ForAttributeName = "asp-for";

    /// <summary>
    /// Creates a new <see cref="LabelTitleTagHelper"/>.
    /// </summary>
    /// <param name="generator">The <see cref="IHtmlGenerator"/>.</param>
    public LabelTitleTagHelper(IHtmlGenerator generator)
    {
        Generator = generator;
    }

    /// <inheritdoc />
    public override int Order
    {
        get
        {
            return -1000;
        }
    }

    [HtmlAttributeNotBound]
    [ViewContext]
    public ViewContext ViewContext { get; set; }

    protected IHtmlGenerator Generator { get; }

    /// <summary>
    /// An expression to be evaluated against the current model.
    /// </summary>
    [HtmlAttributeName(ForAttributeName)]
    public ModelExpression TitleFor { get; set; }

    /// <inheritdoc />
    /// <remarks>Does nothing if <see cref="TitleFor"/> is <c>null</c>.</remarks>
    public override async Task ProcessAsync(TagHelperContext context, TagHelperOutput output)
    {
        if (context == null)
        {
            throw new ArgumentNullException(nameof(context));
        }

        if (output == null)
        {
            throw new ArgumentNullException(nameof(output));
        }

        var metadata = TitleFor.Metadata;

        if (metadata == null)
        {
            throw new InvalidOperationException(string.Format("No provided metadata ({0})", ForAttributeName));
        }

        if (!string.IsNullOrWhiteSpace(metadata.Description))
            output.Attributes.SetAttribute("title", metadata.Description);
    }
}

Bu DisplayAttribute model ma'lumotlar izohidan Description xususiyati bilan yangi title atributini yaratadi.

Chiroyli tomoni shundaki, siz yaratgan iskala ko'rinishlariga tegishingiz shart emas! Chunki bu teg yordamchisi allaqachon mavjud label elementining asp-for atributiga qaratilgan!

Yakob Gade'aga qo'shimcha ravishda ajoyib javob:

Agar siz DisplayAttribute oʻrniga DescriptionAttribute ni qoʻllab-quvvatlashingiz kerak boʻlsa, MetadataProviderni bekor qilsak ham uning ajoyib yechimi ishlaydi:

public class ExtendedModelMetadataProvider : DataAnnotationsModelMetadataProvider
{
    protected override ModelMetadata CreateMetadata(IEnumerable<System.Attribute> attributes, Type containerType, Func<object> modelAccessor, Type modelType, string propertyName)
    {
        //Possible Multiple Enumerations on IEnumerable fix
        var attributeList = attributes as IList<System.Attribute> ?? attributes.ToList();

        //Default behavior
        var data = base.CreateMetadata(attributeList, containerType, modelAccessor, modelType, propertyName);

        //Bind DescriptionAttribute
        var description = attributeList.SingleOrDefault(a => typeof(DescriptionAttribute) == a.GetType());
        if (description != null)
        {
            data.Description = ((DescriptionAttribute)description).Description;
        }

        return data;
    }
}

Bu Global.asax.cs-dagi Application_Start usulida registrlar bo'lishi kerak:

ModelMetadataProviders.Current = new ExtendedModelMetadataProvider();

HANDL javobi, ASP.NET Core 2.0 uchun yangilangan

using System;
using System.Linq.Expressions;
using Microsoft.AspNetCore.Html;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.AspNetCore.Mvc.ViewFeatures.Internal;

public static class HtmlExtensions
{
    public static IHtmlContent DescriptionFor<TModel, TValue>(this IHtmlHelper<TModel> html, Expression<Func<TModel, TValue>> expression)
    {
        if (html == null) throw new ArgumentNullException(nameof(html));
        if (expression == null) throw new ArgumentNullException(nameof(expression));

        var modelExplorer = ExpressionMetadataProvider.FromLambdaExpression(expression, html.ViewData, html.MetadataProvider);
        if (modelExplorer == null) throw new InvalidOperationException($"Failed to get model explorer for {ExpressionHelper.GetExpressionText(expression)}");

        return new HtmlString(modelExplorer.Metadata.Description);
    }
}

Siz har doim o'zingizning shaxsiy kengaytmangizni quyidagicha yaratishingiz mumkin:

    public static MvcHtmlString ToolTipLabel (string resourceKey, string text, bool isRequired, string labelFor = "", string labelId = "",string className="")
    {
        string tooltip = string.Empty;

        StringBuilder sb = new StringBuilder();

        if (!string.IsNullOrEmpty(resourceKey))
        {
            var resources = GetAllResourceValues();

            if (resources.ContainsKey(resourceKey))
            {
                tooltip = resources[resourceKey].Value;
            }
        }

        sb.Append("<label");

        if (!string.IsNullOrEmpty(labelFor))
        {
            sb.AppendFormat(" for=\"{0}\"", labelFor);
        }

        if (!string.IsNullOrEmpty(labelId))
        {
            sb.AppendFormat(" Id=\"{0}\"", labelId);
        }

        if (!string.IsNullOrEmpty(className))
        {
            sb.AppendFormat(" class=\"{0}\"", className);
        }

        if (!string.IsNullOrEmpty(tooltip))
        {

            sb.AppendFormat(" data-toggle='tooltip' data-placement='auto left' title=\"{0}\"",tooltip);

        }
        if (isRequired)
        {
            sb.AppendFormat("><em class='required'>*</em> {0} </label></br>", text);
        }
        else
        {
            sb.AppendFormat(">{0}</label></br>", text);
        }
        return MvcHtmlString.Create(sb.ToString());
    }

va uni shunday ko'rinishda olish mumkin:

@HtmlExtension.ToolTipLabel(" "," ",true," "," "," ")