在Startup.cs文件中，将中间件的顺序从下往上进行排列，并确保异常处理中间件是最先被注册的。示例代码如下所示：

public void Configure(IApplicationBuilder app, IHostingEnvironment env) { if (env.IsDevelopment()) { app.UseDeveloperExceptionPage(); } else { app.UseExceptionHandler("/Error"); }

app.UseStatusCodePagesWithReExecute("/Error/{0}");
app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseCookiePolicy();

app.UseMiddleware();

app.UseMvc(routes =>
{
    routes.MapRoute(
        name: "default",
        template: "{controller=Home}/{action=Index}/{id?}");
});

}

其中，ExceptionMiddleware是自定义的异常处理中间件，代码示例如下：

public class ExceptionMiddleware { private readonly RequestDelegate _next; private readonly ILogger _logger;

public ExceptionMiddleware(RequestDelegate next, ILogger logger)
{
    _next = next;
    _logger = logger;
}

public async Task InvokeAsync(HttpContext context)
{
    try
    {
        await _next(context);
    }
    catch (Exception ex)
    {
        _logger.LogError($"Something went wrong: {ex}");
        await HandleExceptionAsync(context, ex);
    }
}

private async Task HandleExceptionAsync(HttpContext context, Exception ex)
{
    context.Response.ContentType = "application/json";
    context.Response.StatusCode = (int)HttpStatusCode.InternalServerError;

    await context.Response.WriteAsync(new ErrorDetails()
    {
        StatusCode = context.Response.StatusCode,
        Message = "Internal Server Error from the custom middleware."
    }.ToString());
}

}

在以上示例代码中，ExceptionMiddleware仅仅是针对服务器端异常的处理，还需要在客户端代码中进行错误处理，代码示例如下：

try { // 执行某些代码块 } catch (error) { console.error(error); // 显示错误信息到视图上 }

使用以上方法可以实现ASP.Net Core应用中的全局异常处理。