How to customize default error pages in azure web app for linux?

I find a docs about creating Application Gateway custom error pages,maybe it's good for you. custom error pages How to create custom error page in code.

We also can handle it by code.Here is my suggest.

Errors like 500, we can handle it by filter,

public class ErrorPageFilter : ActionFilterAttribute
{
    public override void OnResultExecuted(ResultExecutedContext context)
    {
        if (context.HttpContext.Response.StatusCode == 500)
        {
            context.HttpContext.Response.Redirect("error/500");
        }
        base.OnResultExecuted(context);
        }
}

[ErrorPageFilter]
public abstract class PageController
{}

For .netcore mvc project, it also comes with pipeline processing for error pages when it is created.

In startup.cs,

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
        //dev env show error page
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }
        else
        {
            //prod env show custom page
            app.UseExceptionHandler("/Home/Error");
            app.UseHsts();
        }
}

//In HomeController has this function,
//You just replace cshtml file by you want
[ResponseCache(Duration = 0, Location = ResponseCacheLocation.None, NoStore =     true)]
public IActionResult Error()
{
    return View(new ErrorViewModel { RequestId = Activity.Current?.Id ??     HttpContext.TraceIdentifier });
}

Errors like 404, we can,

In startup.cs file find configure function,then add below code,

  app.UseStatusCodePagesWithReExecute("/error/{0}");

Then add error Controller,

public class ErrorController : Controller
{
        /// <summary>
        /// In content in {0} is error code
        /// </summary>
        /// <returns></returns>
        [Route("/error/{0}")]
        public IActionResult Page()
        {
            //Jump to 404 error page
            if (Response.StatusCode == 404)
            {
                return View("/views/error/notfound.cshtml");
            }
            return View();
        }
}

Pay attention, if use ErroeController( handle 404 error), pls don't use app.UseExceptionHandler("/Home/Error"), you just need handle error in Controller.