写在前面

微软在更新.Net Core 版本的时候，动作往往很大，使得每次更新版本的时候都得小心翼翼，坑实在是太多。往往是悄咪咪的移除了某项功能或者组件，或者不在支持 XX 方法，这就很花时间去找回需要的东西了，下面是个人在迁移.Net Core WebApi 项目过程中遇到的问题汇总：

开始迁移

app.UseRouting();
app.UseEndpoints(endpoints =>
{
endpoints.MapControllers();
endpoints.MapControllerRoute(
name: "areas",
pattern: "{area:exists}/{controller=Home}/{action=Index}/{id?}");
endpoints.MapControllerRoute(
name: "default",
pattern: "{controller=Home}/{action=Index}/{id?}");
});

坑

这时候你以为结束了，兴高采烈的去服务器装好 runningTime 和 hosting 相应的版本，运行……

HTTP Error 500.30 – ANCM In-Process Start Failure

直接 cmd，进入到发布目录，执行

E:你的路径>dotnet xxx.dll

services.AddAutoMapper(AppDomain.CurrentDomain.GetAssemblies());

搜索最新的 AutoMapper 根本没更新或改变，所以不是这个组件的问题。

尝试下载补丁 Windows6.1-KB974405-x64.msu ，无果……

卸载 sdk 重置，无果……

修改 web.config，无果……

修改应用池 32 位，无果……

最后，查看发布：勾选上【删除现有文件】，解决……

Endpoint contains CORS metadata, but a middleware was not found that supports CORS.

app.UseRouting();
//跨域
app.UseCors(one);
app.UseCors(two);
……
app.UseEndpoints(endpoints => ……

The JSON value could not be converted to System.Int32. Path……

运行之后，有些接口没有数据返回，而有些直接报错了。原因又是爸爸把 Newtonsoft.Json 移除，使用内置的 System.Text.Json，所以依赖于 Newtonsoft.Json 的组件将不可用，那么，只能手动添加。

Install-Package Microsoft.AspNetCore.Mvc.NewtonsoftJson -Version 3.1.5

public void ConfigureServices(IServiceCollection services)
{
services.AddControllers().AddNewtonsoftJson();
   ……
}

授权相关

基于策略授权，我想在座的加班狗都是大同小异，在 2.2 以前：

public class PolicyHandler : AuthorizationHandler<PolicyRequirement>
{
/// <summary>
/// 授权方式（cookie, bearer, oauth, openid）
/// </summary>
public IAuthenticationSchemeProvider Schemes { get; set; }


private IConfiguration _configuration;


/// <summary>
/// ctor
/// </summary>
/// <param name="configuration"></param>
/// <param name="schemes"></param>
/// <param name="jwtApp"></param>
public PolicyHandler(IConfiguration configuration, IAuthenticationSchemeProvider schemes)
{
Schemes = schemes;
_jwtApp = jwtApp;
_configuration = configuration;
}


/// <summary>
/// 授权处理
/// </summary>
/// <param name="context"></param>
/// <param name="requirement"></param>
protected override async Task HandleRequirementAsync(AuthorizationHandlerContext context, PolicyRequirement requirement)
{
var httpContext = (context.Resource as AuthorizationFilterContext).HttpContext;


//获取授权方式
var defaultAuthenticate = await Schemes.GetDefaultAuthenticateSchemeAsync();
if (defaultAuthenticate != null)
{
//验证签发的用户信息
var result = await httpContext.AuthenticateAsync(defaultAuthenticate.Name);
if (result.Succeeded)
{
httpContext.User = result.Principal;


//判断是否过期
var expirationTime = DateTime.Parse(httpContext.User.Claims.SingleOrDefault(s => s.Type == ClaimTypes.Expiration).Value);
if (expirationTime >= DateTime.UtcNow)
{
//你的校验方式
//todo
context.Succeed(requirement);
}
else
{
HandleBlocked(context, requirement);
}
return;
}
}
HandleBlocked(context, requirement);
}


/// <summary>
/// 验证失败返回
/// </summary>
private void HandleBlocked(AuthorizationHandlerContext context, PolicyRequirement requirement)
{
var authorizationFilterContext = context.Resource as AuthorizationFilterContext;
authorizationFilterContext.Result = new Microsoft.AspNetCore.Mvc.JsonResult(new UnAuthorizativeResponse()) { StatusCode = 202 };
//不要调用 context.Fail(),设置为 403 会显示不了自定义信息,改为 Accepted202,由客户端处理,;
context.Succeed(requirement);
}
}

然后发现升级到 3.0 之后，

var httpContext = (context.Resource as AuthorizationFilterContext).HttpContext;

/// <summary>
/// 验证失败返回
/// </summary>
private void HandleBlocked(AuthorizationHandlerContext context, PolicyRequirement requirement)
{
context.Fail();
}

services.AddHttpContextAccessor();

.AddJwtBearer(s =>
{
//3、添加 Jwt bearer
s.TokenValidationParameters = new TokenValidationParameters
{
ValidIssuer = issuer,
ValidAudience = audience,
IssuerSigningKey = key,
//允许的服务器时间偏差的偏移量
ClockSkew = TimeSpan.FromSeconds(5),
ValidateLifetime = true
};
s.Events = new JwtBearerEvents
{
OnAuthenticationFailed = context =>
{
//Token 过期
if (context.Exception.GetType() == typeof(SecurityTokenExpiredException))
{
context.Response.Headers.Add("Token-Expired", "true");
}
return Task.CompletedTask;
},
OnChallenge = context =>
{
context.HandleResponse();
context.Response.StatusCode = StatusCodes.Status200OK;
context.Response.ContentType = "application/json";
//无授权返回自定义信息
context.Response.WriteAsync(JsonConvert.SerializeObject(new UnAuthorizativeResponse()));
return Task.CompletedTask;
}
};
});

Startup.Configure中启用 Authentication，注意顺序

app.UseRouting();
//跨域
app.UseCors(one);
app.UseCors(two);
……
//启用 Authentication
app.UseAuthorization();
app.UseAuthentication();
app.UseEndpoints(endpoints => ……

文件下载

单独封装的 HttpContext 下载方法：

public static void DownLoadFile(this HttpContext context,string fileName, byte[] fileByte, string contentType = "application/octet-stream")
{
int bufferSize = 1024;


context.Response.ContentType = contentType;
context.Response.Headers.Append("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(fileName));
context.Response.Headers.Append("Charset", "utf-8");
context.Response.Headers.Append("Access-Control-Expose-Headers", "Content-Disposition");


//context.Response.Headers.Append("Access-Control-Allow-Origin", "*");
//使用 FileStream 开始循环读取要下载文件的内容
using (Stream fs = new MemoryStream(fileByte))
{
using (context.Response.Body)
{
long contentLength = fs.Length;
context.Response.ContentLength = contentLength;


byte[] buffer;
long hasRead = 0;
while (hasRead < contentLength)
{
if (context.RequestAborted.IsCancellationRequested)
{
break;
}


buffer = new byte[bufferSize];
//从下载文件中读取 bufferSize(1024 字节)大小的内容到服务器内存中
int currentRead = fs.Read(buffer, 0, bufferSize);
context.Response.Body.Write(buffer, 0, currentRead);
context.Response.Body.Flush();
hasRead += currentRead;
}
}
}
}

下载的时候发现以下错误：Synchronous operations are disallowed. Call WriteAsync or set AllowSynchronousIO to true instead.

2020-06-29 14:18:38,898 [109] ERROR System.String - System.InvalidOperationException: Synchronous operations are disallowed. Call WriteAsync or set AllowSynchronousIO to true instead.
at Microsoft.AspNetCore.Server.IIS.Core.HttpResponseStream.Write(Byte[] buffer, Int32 offset, Int32 count)
at Microsoft.AspNetCore.Server.IIS.Core.WrappingStream.Write(Byte[] buffer, Int32 offset, Int32 count)
at DigitalCertificateSystem.Common.Extensions.HttpContextExtension.DownLoadFile(HttpContext context, String fileName, Byte[] fileByte, String contentType) in ……

context.Response.Body.WriteAsync(buffer, 0, currentRead);

这才顺利完成了更新。真的太坑了，不过也感觉微软的抽象化做得很好，按需引入，减少项目的冗余。

更多升级指南请参考“孙子兵法”：

https://docs.microsoft.com/zh-cn/aspnet/core/migration/22-to-30?view=aspnetcore-2.1&tabs=visual-studio