ASP.NET Core是微軟新推出的支持跨平臺(tái)、高性能、開(kāi)源的開(kāi)發(fā)框架，它的優(yōu)勢(shì)不必多說(shuō)，因?yàn)橐呀?jīng)說(shuō)得太多了。當(dāng)然，現(xiàn)在依然有著數(shù)量龐大的系統(tǒng)運(yùn)行于.NET Framework上，由于有大量的Break Changes，很多項(xiàng)目項(xiàng)目團(tuán)隊(duì)也不敢貿(mào)然升級(jí)，其中的考量也不全部是技術(shù)原因，更多的可能還是業(yè)務(wù)推進(jìn)因素。
小編自年前開(kāi)始考慮升級(jí)一套電商系統(tǒng)，原先是基于.NET Framework 4.5的，打算直接升級(jí)到.NET Core 3.1，由于系統(tǒng)規(guī)模比較龐大，所以一旦開(kāi)工就是一個(gè)漫長(zhǎng)的工程。
年前第一次重構(gòu)時(shí)，由于低估這套系統(tǒng)的復(fù)雜性再加上有些冒進(jìn)，步子邁得有點(diǎn)大，出現(xiàn)了很多問(wèn)題，不得不重新開(kāi)始。這一次重構(gòu)先易后難，步步為營(yíng)，難題統(tǒng)一在后面解決，到現(xiàn)在已經(jīng)完成了全部工程的百分之八十，后面的也沒(méi)有太困難了，所以特地抽出時(shí)間小結(jié)一下。
類庫(kù)部分的遷移應(yīng)該是最簡(jiǎn)單的了，我是創(chuàng)建了一個(gè)新的類庫(kù)，然后把代碼copy過(guò)去，很少有地方需要修改，當(dāng)然了有一些引用的第三方類庫(kù)需要特殊對(duì)待，如Automapper、Autofac、FluentValidation等，這些也很簡(jiǎn)單，看看文檔就行。
.NET Framework中，會(huì)有一些常用的封裝庫(kù)，如Session、Cookie和HttpRuntime等，這些變化比較大，所以自己在Startup中啟用。
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，可以通過(guò)HttpContext調(diào)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");HttpRuntime的使用，可以通過(guò)IMemoryCache替換，具體的使用方法可參考MSDNSystem.Drawing已經(jīng)不存在了，我使用的是ZKWeb.System.Drawing，基本上類名、枚舉名沒(méi)變化，只是命名空間Drawing變成了DrawingCore依賴注入部分全部遷移到Startup.ConfigureServicesController部分順便說(shuō)一下，靜態(tài)資源部分，如JS、CSS、Image、Font這些復(fù)制到wwwroot目錄上，另外app.UseStaticFiles();會(huì)在模板中出現(xiàn)。
1、獲取Controller及Action信息，可以通過(guò)RouteData.Values["controller"].ToString()，RouteData.Values["action"].ToString()
2、很多的信息都放到了Request.Header[“”]中，如果之前可以用過(guò)Request直接點(diǎn)出來(lái)的，但是現(xiàn)在點(diǎn)不出來(lái)了，可以嘗試使用這種方式，說(shuō)不準(zhǔn)會(huì)有意外驚喜。另外有一個(gè)相關(guān)的常量在這里出示一下，使用方式即Request.Header[HeaderNames.Authority]，當(dāng)然Request.HttpMethod 改為了 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: }3、Request.IsAjaxRequest
這個(gè)已經(jīng)不存在了，可以自行實(shí)現(xiàn)。
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注冊(cè)
之前的AreaRegistration已經(jīng)不存在，如果需要設(shè)置Area，可以在每個(gè)Controller上設(shè)置[Area(“Admin”)]，路由處的注冊(cè)可以考慮如下方式
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: });5、AbsoluteUri也已經(jīng)不存在了，但是可以通過(guò)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、過(guò)濾器
之前繼承ActionFilterAttribute，現(xiàn)在實(shí)現(xiàn)IActionFilter，注冊(cè)方式為services.AddMvc(o=>o.Filters.Add(new XX()))，當(dāng)然之前的很多過(guò)濾器或者Controller基類方法已經(jīng)不存在了，如Controller OnAuthentication。
IResultFilter中的OnResultExecuting(ResultExecutingContext filterContext)需要通過(guò)filterContext.Controller as Controller來(lái)獲取默認(rèn)的Controller。
最后有一個(gè)比較重要的類ActionDescriptor，ControllerDescriptor繼承自ActionDescriptor，這里可以通過(guò)類型轉(zhuǎn)換獲取相關(guān)信息。
之前有很多的FilterAttribute也可以通過(guò)中間件來(lái)取代。
7、Action上被去掉的Attribute，如[ValidateInput(false)]，[ChildActionOnly]
View部分1、頁(yè)面基類型及擴(kuò)展
之前我們創(chuàng)建頁(yè)面基類型，是通過(guò)繼承System.Web.Mvc.WebViewPage<TModel>來(lái)實(shí)現(xiàn)，現(xiàn)在我們可以通過(guò)RazorPage<TModel>來(lái)取代。
擴(kuò)展HtmlHelper也換成了IHtmlHelper接口。HtmlString也替換了MvcHtmlString，更上層也以接口方式來(lái)取代IHtmlContent。
1: public static IHtmlContent AlignTypeSelect(this IHtmlHelper _html, string xxxxx) 2: { 3: //your code 4: return new HtmlString(html.ToString()); 5: }2、Ajax.BeginForm換成了<form asp-controller="DistributorGrade" asp-action="Save" id="addform" data-ajax="true" data-ajax-method="post" data-ajax-begin="begin" data-ajax-success="success">。當(dāng)前.NET Core 依然支持Html.BeginForm，不過(guò)我建議大家有時(shí)間的時(shí)候都替換一下，具體請(qǐng)參考下一條。
3、第2條出現(xiàn)的asp-action等是通過(guò)Razor Tag Helpers來(lái)實(shí)現(xiàn)的，很多的自定義需要加入到_ViewImports.cshtml，當(dāng)然一些引用也可以統(tǒng)一放到這里，如@using Microsoft.AspNetCore.Routing，這樣就可以在當(dāng)前的Area中作為全局引用了。
Razor Tag Help是一個(gè)十分重要的功能，它使得.NET Core MVC的開(kāi)發(fā)更像是在寫Html語(yǔ)言，更加的清晰，更加具有生產(chǎn)力。
如@Html.TextBoxFor()可以用通過(guò)<input asp-for=””/>替換，以下圖片摘自MSDN：
Framework MVC的寫法
Core MVC的寫法
一些Tag Help集錦：
Built-in ASP.NET Core Tag HelpersAnchor 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可以通過(guò)ViewComponents來(lái)取代
1: public class XXXXViewComponent : ViewComponent 2: { 3: public IViewComponentResult Invoke() 4: { 5: return this.View(""); 6: } 7: }調(diào)用方式是await Component.InvokeAsync(“XXXXViewComponent“)，詳情請(qǐng)點(diǎn)擊鏈接
5、@MvcHtmlString.Create()可以使用new Microsoft.AspNetCore.Html.HtmlString()取代
6、IP地址可以通過(guò)HttpRequest.HttpContext.Connection.RemoteIpAddress獲取
7、之前通過(guò)@helper 定義頁(yè)面的函數(shù)，這個(gè)已經(jīng)被去掉了，現(xiàn)在可以通過(guò)@functions來(lái)取代
小結(jié)限于篇幅，先總結(jié)這么多，系統(tǒng)尚未完全結(jié)束，不過(guò)升級(jí)到.NET Core是一個(gè)非常棒的過(guò)程，可以更好地體驗(yàn).NET Core的強(qiáng)大。如果小伙伴在升級(jí)過(guò)程中也遇到了很多問(wèn)題，希望這篇文章可以給大家一些幫助，另外我沒(méi)有寫到的，大家可以留個(gè)言，我統(tǒng)一收集一下。
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