.net - 用于访问 Gravatar 图像的 ASP.NET MVC 帮助程序

Question

虽然 Gravatar 服务的 API(嗯，它实际上只是一个 URL)非常简单，但是否有一个简单的辅助方法可以很好地反射(reflect) Gravatar 可用的所有选项？

• 图像大小
• 默认图片(当用户未指定时)
• 评级(G/PG/R/X)

理想情况下，这将是一个 HtmlHelper 扩展方法。

我的目标是 .NET4 上的 MVC2，但我想其他人也会对早期版本的选项感兴趣。

编辑实现也应该允许为生成的 HTML 元素提供附加属性。

Answer 1

感谢您的回答。最后，我编写了自己的解决方案，因此我将其发布在这里，供其他可能觉得它有用的人使用。

它满足 Gravatar 目前支持的所有功能，如问题中所列。

像这样使用它:

<%= Html.Gravatar(Model.User.EmailAddress) %>

我为任何呃选项提供了可选参数。这些可以组合起来。

// Use a specific image size (the default is 80px)
Html.Gravatar(Model.User.EmailAddress, size:64)

// Specify what image should appear if the email address is not
// associated with a Gravatar account
Html.Gravatar(Model.User.EmailAddress,
              defaultImage:GravatarDefaultImage.Identicon)

// Specify the maximum rating allowed for images
Html.Gravatar(Model.User.EmailAddress, rating:GravatarRating.Pg)

// Add any additional HTML attributes for the <img /> tag
Html.Gravatar(Model.User.EmailAddress,
              htmlAttributes:new { @class = "gravatar" })

代码如下:

using System;
using System.Diagnostics;
using System.Security.Cryptography;
using System.Text;
using System.Web.Mvc;
using System.Web.Routing;

namespace SampleNamespace
{
    public static class HtmlHelperGravatar
    {
        /// <summary>
        /// Creates HTML for an <c>img</c> element that presents a Gravatar icon.
        /// </summary>
        /// <param name="html">The <see cref="HtmlHelper"/> upon which this extension method is provided.</param>
        /// <param name="email">The email address used to identify the icon.</param>
        /// <param name="size">An optional parameter that specifies the size of the square image in pixels.</param>
        /// <param name="rating">An optional parameter that specifies the safety level of allowed images.</param>
        /// <param name="defaultImage">An optional parameter that controls what image is displayed for email addresses that don't have associated Gravatar icons.</param>
        /// <param name="htmlAttributes">An optional parameter holding additional attributes to be included on the <c>img</c> element.</param>
        /// <returns>An HTML string of the <c>img</c> element that presents a Gravatar icon.</returns>
        public static string Gravatar(this HtmlHelper html,
                                      string email, 
                                      int? size = null,
                                      GravatarRating rating = GravatarRating.Default,
                                      GravatarDefaultImage defaultImage = GravatarDefaultImage.MysteryMan,
                                      object htmlAttributes = null)
        {
            var url = new StringBuilder("//www.gravatar.com/avatar/", 90);
            url.Append(GetEmailHash(email));

            var isFirst = true;
            Action<string,string> addParam = (p,v) =>
                {
                    url.Append(isFirst ? '?' : '&');
                    isFirst = false;
                    url.Append(p);
                    url.Append('=');
                    url.Append(v);
                };

            if (size != null)
            {
                if (size < 1 || size > 512)
                    throw new ArgumentOutOfRangeException("size", size, "Must be null or between 1 and 512, inclusive.");
                addParam("s", size.Value.ToString());
            }

            if (rating != GravatarRating.Default)
                addParam("r", rating.ToString().ToLower());

            if (defaultImage != GravatarDefaultImage.Default)
            {
                if (defaultImage==GravatarDefaultImage.Http404)
                    addParam("d", "404");
                else if (defaultImage==GravatarDefaultImage.Identicon)
                    addParam("d", "identicon");
                if (defaultImage==GravatarDefaultImage.MonsterId)
                    addParam("d", "monsterid");
                if (defaultImage==GravatarDefaultImage.MysteryMan)
                    addParam("d", "mm");
                if (defaultImage==GravatarDefaultImage.Wavatar)
                    addParam("d", "wavatar");
            }

            var tag = new TagBuilder("img");
            tag.MergeAttributes(new RouteValueDictionary(htmlAttributes));
            tag.Attributes.Add("src", url.ToString());

            if (size!=null)
            {
                tag.Attributes.Add("width", size.ToString());
                tag.Attributes.Add("height", size.ToString());
            }

            return tag.ToString();
        }

        private static string GetEmailHash(string email)
        {
            if (email == null)
                return new string('0', 32);

            email = email.Trim().ToLower();

            var emailBytes = Encoding.ASCII.GetBytes(email);
            var hashBytes = new MD5CryptoServiceProvider().ComputeHash(emailBytes);

            Debug.Assert(hashBytes.Length == 16);

            var hash = new StringBuilder();
            foreach (var b in hashBytes)
                hash.Append(b.ToString("x2"));
            return hash.ToString();
        }
    }

    public enum GravatarRating
    {
        /// <summary>
        /// The default value as specified by the Gravatar service.  That is, no rating value is specified
        /// with the request.  At the time of authoring, the default level was <see cref="G"/>.
        /// </summary>
        Default,

        /// <summary>
        /// Suitable for display on all websites with any audience type.  This is the default.
        /// </summary>
        G,

        /// <summary>
        /// May contain rude gestures, provocatively dressed individuals, the lesser swear words, or mild violence.
        /// </summary>
        Pg,

        /// <summary>
        /// May contain such things as harsh profanity, intense violence, nudity, or hard drug use.
        /// </summary>
        R,

        /// <summary>
        /// May contain hardcore sexual imagery or extremely disturbing violence.
        /// </summary>
        X
    }

    public enum GravatarDefaultImage
    {
        /// <summary>
        /// The default value image.  That is, the image returned when no specific default value is included
        /// with the request.  At the time of authoring, this image is the Gravatar icon.
        /// </summary>
        Default,

        /// <summary>
        /// Do not load any image if none is associated with the email hash, instead return an HTTP 404 (File Not Found) response.
        /// </summary>
        Http404,

        /// <summary>
        /// A simple, cartoon-style silhouetted outline of a person (does not vary by email hash).
        /// </summary>
        MysteryMan,

        /// <summary>
        /// A geometric pattern based on an email hash.
        /// </summary>
        Identicon,

        /// <summary>
        /// A generated 'monster' with different colors, faces, etc.
        /// </summary>
        MonsterId,

        /// <summary>
        /// Generated faces with differing features and backgrounds.
        /// </summary>
        Wavatar
    }
}