Multi tool use

Unable to activate type 'Microsoft.AspNetCore.Mvc.Razor.RazorViewEngine when starting app

Asp.net core 2.1

Startup.cs:

public void ConfigureServices(IServiceCollection services)
{
services
.AddMvc()
.SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
}

public void Configure(IApplicationBuilder app)
{
if (this.HostingEnvironment.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}

app.UseDatabaseErrorPage();
app.UseDeveloperExceptionPage();
app.UseMvc(routes => {
routes.MapRoute(
name: "default",
template: "{controller=GenericController}/{action=Get}");
});
}


Error message:

InvalidOperationException: Unable to activate type
'Microsoft.AspNetCore.Mvc.Razor.RazorViewEngine'. The following
constructors are ambiguous: Void
.ctor(Microsoft.AspNetCore.Mvc.Razor.IRazorPageFactoryProvider,
Microsoft.AspNetCore.Mvc.Razor.IRazorPageActivator,
System.Text.Encodings.Web.HtmlEncoder,
Microsoft.Extensions.Options.IOptions1[Microsoft.AspNetCore.Mvc.Razor.RazorViewEngineOptions],
Microsoft.AspNetCore.Razor.Language.RazorProject,
Microsoft.Extensions.Logging.ILoggerFactory,
System.Diagnostics.DiagnosticSource) Void
.ctor(Microsoft.AspNetCore.Mvc.Razor.IRazorPageFactoryProvider,
Microsoft.AspNetCore.Mvc.Razor.IRazorPageActivator,
System.Text.Encodings.Web.HtmlEncoder,
Microsoft.Extensions.Options.IOptions1[Microsoft.AspNetCore.Mvc.Razor.RazorViewEngineOptions],
Microsoft.AspNetCore.Razor.Language.RazorProjectFileSystem,
Microsoft.Extensions.Logging.ILoggerFactory,
System.Diagnostics.DiagnosticSource)

1[Microsoft.AspNetCore.Mvc.Razor.RazorViewEngineOptions],
Microsoft.AspNetCore.Razor.Language.RazorProject,
Microsoft.Extensions.Logging.ILoggerFactory,
System.Diagnostics.DiagnosticSource) Void
.ctor(Microsoft.AspNetCore.Mvc.Razor.IRazorPageFactoryProvider,
Microsoft.AspNetCore.Mvc.Razor.IRazorPageActivator,
System.Text.Encodings.Web.HtmlEncoder,
Microsoft.Extensions.Options.IOptions

1 Answer
1

Sounds like an issue with upgrading. I'm guessing you might have recently upgraded from 1.x?

I would try this:

Nuget packages -> Make sure your only "Web"-related installed packages are Microsoft.AspNetCore.App and Microsoft.NETCore.App. You'll probably have some CodeGeneration package as well, which shouldn't be a concern. Versions should be around 2.1.

Make sure your .csproj is cleared from everything mentioned in this migration guide: https://docs.microsoft.com/en-us/aspnet/core/migration/1x-to-2x/?view=aspnetcore-2.1

A final hail mary is clearing any weird stuff in any .config files and/or reinstalling the Nuget-packages. (And in worst case, check all your references for any non 2.1 web-related DLLs)

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