转换为 AS.NET Core 3.1 后 MVC 找不到视图

Question

We are converting an MVC/Angular web site from AS.NET Core 2.2 to AS.NET Core 3.1. I have got the build to run with no errors or warnings, but when it starts up (in Visual Studio 2019), it looks for Home/Index, finds the controller fine, and looks for the Home/Index View, but it fails to find it even though it is there (in Views/Home/Index.cshtml), right where it's supposed to be (and right where it's been for the several months that we have been developing this site. I have it now reduced to a test case that I can set the web project file to.netcoreapp2.2 and the site runs fine, then stop it and change the to.netcoreapp3.1, with no other changes, and it fails. The errors are exactly what you would expect if the file were missing:

System.InvalidOperationException: The view 'Index' was not found. The following locations were searched:

/Views/Home/Index.cshtml

/Views/Shared/Index.cshtml

/Pages/Shared/Index.cshtml

But the file is there. I'm completely baffled.

Can anyone give me a hint as to what's going on?

Thanks.

Answer 1

We just had a similar issue with partials: after upgrading a web app from core 2.2 to 3.1 partial views could not be found. The solution for us was to replace this...

services.AddMvc();

... with ...

services.AddControllersWithViews();
services.AddRazorPages().AddRazorRuntimeCompilation();

Although I believe .AddMvc() is equivalent to .AddControllersWithViews() plus .AddRazorPages it doesn't include the runtime compilation part out of the box.

Answer 2

Check the part about routing adjustments - see Migrate from ASP.NET Core 2.2 to 3.0

Most likely you need to change this in your Startup class:

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

with that:

app.UseEndpoints(endpoints =>
    {
        endpoints.MapControllerRoute("default", "{controller=Home}/{action=Index}/{id?}");
    });

Answer 3

replace

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

With

`app.UseEndpoints(endpoints =>
        {
            endpoints.MapControllerRoute(
                name: "default",
                pattern: "{controller=Home}/{action=Index}/{id?}");
            endpoints.MapRazorPages();
        });`

They replaced the app.UseMvc to app.UseEndponts when migrating from .Net Core 2 to .Net Core 3.

And also if you have another Views Folder, copy the _ViewImports.cshtml and _ViewStart.cshtml from the existing Views folder to the other Views Folders.

Answer 4

I had same problem.

For me it was this in project file:

<RazorCompileOnBuild>false</RazorCompileOnBuild>
<RazorCompileOnPublish>false</RazorCompileOnPublish>

I had to remove it.

Answer 5

First, you have to install package Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation :

install-package Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation

Then add AddRazorRuntimeCompilation() after services.AddControllersWithViews() line in startup.cs :

services.AddControllersWithViews().AddRazorRuntimeCompilation();