之前的博文 ASP.NET Core中显示自定义错误页面 中的方法是在项目中硬编码实现的，当有多个项目时，就会造成不同项目之间的重复代码，不可取。
在这篇博文中改用middleware实现，并且放在独立的项目中发布成NuGet包，项目中使用时只需安装NuGet包，然后在Startup的Configure()方法中添加如下的一行代码。
app.UseCustomErrorPages();
CustomErrorPagesMiddleware的实现代码如下：
public class CustomErrorPagesMiddleware
{
private readonly RequestDelegate _next;
private readonly ILogger _logger; public CustomErrorPagesMiddleware(
RequestDelegate next,
ILoggerFactory loggerFactory)
{
_next = next;
_logger = loggerFactory.CreateLogger<CustomErrorPagesMiddleware>();
} public async Task Invoke(HttpContext context)
{
try
{
await _next(context);
}
catch (Exception ex)
{
_logger.LogError(, ex, "An unhandled exception has occurred while executing the request"); if (context.Response.HasStarted)
{
_logger.LogWarning("The response has already started, the error page middleware will not be executed.");
throw;
}
try
{
context.Response.Clear();
context.Response.StatusCode = ;
return;
}
catch (Exception ex2)
{
_logger.LogError(, ex2, "An exception was thrown attempting to display the error page.");
}
throw;
}
finally
{
var statusCode = context.Response.StatusCode;
if (statusCode == || statusCode == )
{
await ErrorPage.ResponseAsync(context.Response, statusCode);
}
}
}
}
ErrorPage的实现代码如下：
public static class ErrorPage
{
public static async Task ResponseAsync(HttpResponse response, int statusCode)
{
if (statusCode == )
{
await response.WriteAsync(Page404);
}
else if (statusCode == )
{
await response.WriteAsync(Page500);
}
} private static string Page404 => @"html..."; private static string Page500 => @"html...";
}
CustomErrorPagesExtensions的实现代码如下：
public static class CustomErrorPagesExtensions
{
public static IApplicationBuilder UseCustomErrorPages(this IApplicationBuilder app)
{
if (app == null)
{
throw new ArgumentNullException(nameof(app));
} return app.UseMiddleware<CustomErrorPagesMiddleware>();
}
}
代码参考自：