ASP.NET MVC升级到ASP.NET Core MVC踩坑小结

写在前面

ASP.NET Core是微软新推出的支持跨平台、高性能、开源的开发框架，它的优势不必多说，因为已经说得太多了。当然，现在依然有着数量庞大的系统运行于.NET Framework上，由于有大量的Break Changes，很多项目项目团队也不敢贸然升级，其中的考量也不全部是技术原因，更多的可能还是业务推进因素。

小编自年前开始考虑升级一套电商系统，原先是基于.NET Framework 4.5的，打算直接升级到.NET Core 3.1，由于系统规模比较庞大，所以一旦开工就是一个漫长的工程，我的博客也在很长时间没有再更新，有点对不起读者了。

年前第一次重构时，由于低估这套系统的复杂性再加上有些冒进，步子迈得有点大，出现了很多问题，不得不重新开始。这一次重构先易后难，步步为营，难题统一在后面解决，到现在已经完成了全部工程的百分之八十，后面的也没有太困难了，所以特地抽出时间小结一下。

详细内容

类库部分

类库部分的迁移应该是最简单的了，我是创建了一个新的类库，然后把代码copy过去，很少有地方需要修改，当然了有一些引用的第三方类库需要特殊对待，如Automapper、Autofac、FluentValidation等，这些也很简单，看看文档就行。

.NET Framework中，会有一些常用的封装库，如Session、Cookie和HttpRuntime等，这些变化比较大，所以自己在Startup中启用。

• Session：
• Startup.Configure:

     1:  app.UseSession(new SessionOptions

     2:  {

     3:      Cookie = new CookieBuilder

     4:      {

     5:   

     6:      },

     7:      IdleTimeout = TimeSpan.FromSeconds(1),

     8:      IOTimeout = Timeout.InfiniteTimeSpan

     9:  });

• • • Startup.ConfigureServices:

         1:  services.AddSession();

• 使用Session，可以通过HttpContext调用：

     1:  HttpContext.Session.SetString("sessionId", sessionValue);

     2:  HttpContext.Session.GetString("sessionId");

     3:  context.Session.Remove("sessionId");

• Cookie：

•    1:  Response.Cookies.Append("User", "1", new CookieOptions()

     2:   {

     3:       Expires = DateTime.Now.AddMinutes(10)

     4:   });

     5:  Response.Cookies.Delete("User");

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.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
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• HttpRuntime的使用，可以通过IMemoryCache替换，具体的使用方法可参考MSDN

• System.Drawing已经不存在了，我使用的是ZKWeb.System.Drawing，基本上类名、枚举名没变化，只是命名空间Drawing变成了DrawingCore
• 依赖注入部分全部迁移到Startup.ConfigureServices

Controller部分

顺便说一下，静态资源部分，如JS、CSS、Image、Font这些复制到wwwroot目录上，另外app.UseStaticFiles();会在模板中出现。

1、获取Controller及Action信息，可以通过RouteData.Values["controller"].ToString()，RouteData.Values["action"].ToString()

2、很多的信息都放到了Request.Header[“”]中，如果之前可以用过Request直接点出来的，但是现在点不出来了，可以尝试使用这种方式，说不准会有意外惊喜。另外有一个相关的常量在这里出示一下，使用方式即Request.Header[HeaderNames.Authority]，当然Request.HttpMethod 改为了 Request.Method。

   1:  public static class HeaderNames

   2:    {

   3:      public static readonly string Accept;

   4:      public static readonly string AcceptCharset;

   5:      public static readonly string AcceptEncoding;

   6:      public static readonly string AcceptLanguage;

   7:      public static readonly string AcceptRanges;

   8:      public static readonly string AccessControlAllowCredentials;

   9:      public static readonly string AccessControlAllowHeaders;

  10:      public static readonly string AccessControlAllowMethods;

  11:      public static readonly string AccessControlAllowOrigin;

  12:      public static readonly string AccessControlExposeHeaders;

  13:      public static readonly string AccessControlMaxAge;

  14:      public static readonly string AccessControlRequestHeaders;

  15:      public static readonly string AccessControlRequestMethod;

  16:      public static readonly string Age;

  17:      public static readonly string Allow;

  18:      public static readonly string Authority;

  19:      public static readonly string Authorization;

  20:      public static readonly string CacheControl;

  21:      public static readonly string Connection;

  22:      public static readonly string ContentDisposition;

  23:      public static readonly string ContentEncoding;

  24:      public static readonly string ContentLanguage;

  25:      public static readonly string ContentLength;

  26:      public static readonly string ContentLocation;

  27:      public static readonly string ContentMD5;

  28:      public static readonly string ContentRange;

  29:      public static readonly string ContentSecurityPolicy;

  30:      public static readonly string ContentSecurityPolicyReportOnly;

  31:      public static readonly string ContentType;

  32:      public static readonly string Cookie;

  33:      public static readonly string CorrelationContext;

  34:      public static readonly string Date;

  35:      public static readonly string DNT;

  36:      public static readonly string ETag;

  37:      public static readonly string Expect;

  38:      public static readonly string Expires;

  39:      public static readonly string From;

  40:      public static readonly string Host;

  41:      public static readonly string IfMatch;

  42:      public static readonly string IfModifiedSince;

  43:      public static readonly string IfNoneMatch;

  44:      public static readonly string IfRange;

  45:      public static readonly string IfUnmodifiedSince;

  46:      public static readonly string KeepAlive;

  47:      public static readonly string LastModified;

  48:      public static readonly string Location;

  49:      public static readonly string MaxForwards;

  50:      public static readonly string Method;

  51:      public static readonly string Origin;

  52:      public static readonly string Path;

  53:      public static readonly string Pragma;

  54:      public static readonly string ProxyAuthenticate;

  55:      public static readonly string ProxyAuthorization;

  56:      public static readonly string Range;

  57:      public static readonly string Referer;

  58:      public static readonly string RequestId;

  59:      public static readonly string RetryAfter;

  60:      public static readonly string Scheme;

  61:      public static readonly string SecWebSocketAccept;

  62:      public static readonly string SecWebSocketKey;

  63:      public static readonly string SecWebSocketProtocol;

  64:      public static readonly string SecWebSocketVersion;

  65:      public static readonly string Server;

  66:      public static readonly string SetCookie;

  67:      public static readonly string Status;

  68:      public static readonly string StrictTransportSecurity;

  69:      public static readonly string TE;

  70:      public static readonly string TraceParent;

  71:      public static readonly string TraceState;

  72:      public static readonly string Trailer;

  73:      public static readonly string TransferEncoding;

  74:      public static readonly string Translate;

  75:      public static readonly string Upgrade;

  76:      public static readonly string UpgradeInsecureRequests;

  77:      public static readonly string UserAgent;

  78:      public static readonly string Vary;

  79:      public static readonly string Via;

  80:      public static readonly string Warning;

  81:      public static readonly string WebSocketSubProtocols;

  82:      public static readonly string WWWAuthenticate;

  83:      public static readonly string XFrameOptions;

  84:    }

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color: black;
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background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
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background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

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3、Request.IsAjaxRequest

这个已经不存在了，可以自行实现。

   1:  public static bool IsAjaxRequest(this HttpRequest request)

   2:  {

   3:      if (request == null)

   4:          throw new ArgumentNullException("request");

   5:   

   6:      if (request.Headers != null)

   7:          return request.Headers["X-Requested-With"] == "XMLHttpRequest";

   8:      return false;

   9:  }

4、Area注册

之前的AreaRegistration已经不存在，如果需要设置Area，可以在每个Controller上设置[Area(“Admin”)]，路由处的注册可以考虑如下方式

   1:  app.UseEndpoints(endpoints =>

   2:  {

   3:      endpoints.MapControllerRoute(

   4:          name: "default",

   5:          pattern: "{controller=Home}/{action=Index}/{id?}");

   6:      

   7:      endpoints.MapControllerRoute(

   8:              name: "areas",

   9:              pattern: "{area:exists}/{controller=Home}/{action=Index}/{id?}"

  10:          );

  11:  });

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color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

-->

5、AbsoluteUri也已经不存在了，但是可以通过如下方式取代：

   1:  /// <summary>

   2:  /// Returns the combined components of the request URL in a fully un-escaped form (except for the QueryString)

   3:  /// suitable only for display. This format should not be used in HTTP headers or other HTTP operations.

   4:  /// </summary>

   5:  /// <param name="request">The request to assemble the uri pieces from.</param>

   6:  /// <returns>The combined components of the request URL in a fully un-escaped form (except for the QueryString)

   7:  /// suitable only for display.</returns>

   8:  public static string GetDisplayUrl(this HttpRequest request);

   9:   

  10:  /// <summary>Returns the relative URI.</summary>

  11:  /// <param name="request">The request to assemble the uri pieces from.</param>

  12:  /// <returns>The path and query off of <paramref name="request" />.</returns>

  13:  public static string GetEncodedPathAndQuery(this HttpRequest request);

  14:   

  15:  /// <summary>

  16:  /// Returns the combined components of the request URL in a fully escaped form suitable for use in HTTP headers

  17:  /// and other HTTP operations.

  18:  /// </summary>

  19:  /// <param name="request">The request to assemble the uri pieces from.</param>

  20:  /// <returns>The encoded string version of the URL from <paramref name="request" />.</returns>

  21:  public static string GetEncodedUrl(this HttpRequest request);

6、过滤器

之前继承ActionFilterAttribute，现在实现IActionFilter，注册方式为services.AddMvc(o=>o.Filters.Add(new XX()))，当然之前的很多过滤器或者Controller基类方法已经不存在了，如Controller OnAuthentication。

IResultFilter中的OnResultExecuting(ResultExecutingContext filterContext)需要通过filterContext.Controller as Controller来获取默认的Controller。

最后有一个比较重要的类ActionDescriptor，ControllerDescriptor继承自ActionDescriptor，这里可以通过类型转换获取相关信息。

之前有很多的FilterAttribute也可以通过中间件来取代。

7、Action上被去掉的Attribute，如[ValidateInput(false)]，[ChildActionOnly]

View部分

1、页面基类型及扩展

之前我们创建页面基类型，是通过继承System.Web.Mvc.WebViewPage<TModel>来实现，现在我们可以通过RazorPage<TModel>来取代。

扩展HtmlHelper也换成了IHtmlHelper接口。HtmlString也替换了MvcHtmlString，更上层也以接口方式来取代IHtmlContent。

   1:  public static IHtmlContent XXX(this IHtmlHelper _html, string xxxxx)

   2:  {

   3:      //your code

   4:      return new HtmlString(html.ToString());

   5:  }

2、Ajax.BeginForm换成了<form asp-controller="DistributorGrade" asp-action="Save" id="addform" data-ajax="true" data-ajax-method="post" data-ajax-begin="begin" data-ajax-success="success">。当前.NET Core 依然支持Html.BeginForm，不过我建议大家有时间的时候都替换一下，具体请参考下一条。

3、第2条出现的asp-action等是通过Razor Tag Helpers来实现的，很多的自定义需要加入到_ViewImports.cshtml，当然一些引用也可以统一放到这里，如@using Microsoft.AspNetCore.Routing，这样就可以在当前的Area中作为全局引用了。

Razor Tag Help是一个十分重要的功能，它使得.NET Core MVC的开发更像是在写Html语言，更加的清晰，更加具有生产力。

如@Html.TextBoxFor()可以用通过<input asp-for=””/>替换，以下图片摘自MSDN：

Framework MVC的写法

Core MVC的写法

一些Tag Help集锦：

Built-in ASP.NET Core Tag Helpers

Anchor Tag Helper

Cache Tag Helper

Component Tag Helper

Distributed Cache Tag Helper

Environment Tag Helper

Form Tag Helper

Form Action Tag Helper

Image Tag Helper

Input Tag Helper

Label Tag Helper

Link Tag Helper

Partial Tag Helper

Script Tag Helper

Select Tag Helper

Textarea Tag Helper

Validation Message Tag Helper

Validation Summary Tag Helper

4、@Html.Action和@Html.RenderAction可以通过ViewComponents来取代

   1:  public class XXXXViewComponent : ViewComponent

   2:  {

   3:      public IViewComponentResult Invoke()

   4:      {

   5:          return this.View("");

   6:      }

   7:  }

调用方式是await Component.InvokeAsync(“XXXXViewComponent“)，详情请点击链接

5、@MvcHtmlString.Create()可以使用new Microsoft.AspNetCore.Html.HtmlString()取代

6、IP地址可以通过HttpRequest.HttpContext.Connection.RemoteIpAddress获取

7、之前通过@helper 定义页面的函数，这个已经被去掉了，现在可以通过@functions来取代

小结

限于篇幅，先总结这么多，系统尚未完全结束，不过升级到.NET Core是一个非常棒的过程，可以更好地体验.NET Core的强大。如果小伙伴在升级过程中也遇到了很多问题，希望这篇文章可以给大家一些帮助，另外我没有写到的，大家可以留个言，我统一收集一下。