Localhost not found after migrating application from .net 5 to .net 6 - asp.net-core

Question

I am unable to run my web application project in IIS Express after migrating from .net 5 to .net 6. I get an error stating that "the localhost page can't be found."
From what I've been able to learn, I have gone through the proper steps to migrate between target frameworks. I have changed the target framework to .net 6 in application properties, and I have updated all affected NuGet packages using the NuGet Pkg Manager. No errors are shown when I build the project, and I have ensured Visual Studio is updated to the latest version, 17.2.5 as of this writing.
The IIS Settings in my launchsettings.json file are as follows:
"iisSettings": {
"windowsAuthentication": false,
"anonymousAuthentication": true,
"iisExpress": {
"applicationUrl": "http://localhost:35317",
"sslPort": 44352
}
}
and I do have an Index view return in my home controller. Yet I still get the error that
No webpage was found for the web address: https://localhost:44352/
when I run the application.
I am retaining the "old" hosting model of Startup.cs and Program.cs from the .Net 5 build to save time, as I understand per Microsoft that this is acceptable. No changes have been made to the code in either of those files.
What am I missing?
EDIT: My Program.cs code is below, by request of #adrianMoskal
public class Program
{
public static void Main(string[] args)
{
CreateHostBuilder(args).Build().Run();
}
public static IHostBuilder CreateHostBuilder(string[] args) =>
Host.CreateDefaultBuilder(args)
.ConfigureWebHostDefaults(webBuilder =>
{
webBuilder.UseStartup<Startup>();
});
}
EDIT 2:
Per #adrianMoskal, I updated my Program.cs file to .NET 6 standard. It now looks like this:
var builder = WebApplication.CreateBuilder(args);
// Add DB Contexts and Services here
// Add services to the container.
builder.Services.AddControllersWithViews();
var app = builder.Build();
// Configure the HTTP request pipeline.
if (!app.Environment.IsDevelopment())
{
app.UseExceptionHandler("/Home/Error");
// The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
app.UseHsts();
}
app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseRouting();
app.UseAuthorization();
app.MapControllerRoute(
name: "default",
pattern: "{controller=Home}/{action=Index}/{id?}");
app.Run();
Unfortunately, the error persists.

Answer 1

I created a new project to migrate from .net 5 to .net 6, but no problem, it works fine, I will show you the complete steps：
.csproj:
change Version like below:
<Project Sdk="Microsoft.NET.Sdk.Web">
<PropertyGroup>
<!--<TargetFramework>net5.0</TargetFramework>-->
<TargetFramework>net6.0</TargetFramework>
<RootNamespace>_2022070802</RootNamespace>
<CopyRefAssembliesToPublishDirectory>false</CopyRefAssembliesToPublishDirectory>
</PropertyGroup>
<ItemGroup>
<!--<PackageReference Include="Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation" Version="5.0.16" />-->
<PackageReference Include="Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation" Version="6.0.1" />
</ItemGroup>
</Project>
Then I delete Startup.cs and change Program.cs：
var builder = WebApplication.CreateBuilder(args);
// Add DB Contexts and Services here
// Add services to the container.
builder.Services.AddControllersWithViews();
var app = builder.Build();
// Configure the HTTP request pipeline.
if (!app.Environment.IsDevelopment())
{
app.UseExceptionHandler("/Home/Error");
// The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
app.UseHsts();
}
app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseRouting();
app.UseAuthorization();
app.MapControllerRoute(
name: "default",
pattern: "{controller=Home}/{action=Index}/{id?}");
app.Run();
More detail information, see this link.
You can create a new empty project to migrate from .net 5 to .net 6 and see if the problem still exists.I think this may be the problem caused by some of your configuration, maybe you can check whether your path is correct?

Answer 2

Chen's answer is the correct migration step.
I tried to reproduce your issue. When I comment Index page method in HomeController. And I face the same issue.
So you probably deleted your "Index" action in HomeController.

Answer 3

The answer appears to be "screw you, start over."
I've tried copying my project code to a new .net 6 project -- that is, copying all the views, controllers, and whatnot to the new project and updating the new Program.cs file accordingly -- and I still got the same error. I then tried converting a different .net 5 project to .net 6, and got the same error again. So apparently, converting just doesn't work.
So be it. I quit. I've got too much else to do to worry about this. Thanks to those who responded to this post for trying to help resolve it, anyway.