System.InvalidOperationException: 'Sequence contains more than one matching element'

[DiegoVenancioVieira]

In blazor-server

System.InvalidOperationException
HResult=0x80131509
Message=Sequence contains more than one matching element
Source=System.Linq
StackTrace:
at System.Linq.ThrowHelper.ThrowMoreThanOneMatchException()
at System.Linq.Enumerable.SingleOrDefault[TSource](IEnumerable1 source, Func2 predicate)
at RazorComponentsPreview.RuntimeComponentsGenerator.ReadAllFiles(List`1 razorFiles)
at RazorComponentsPreview.RuntimeComponentsGenerator..ctor(IServiceCollection serviceCollection)
at RazorComponentsPreview.RazorRuntimeCompilationExtensions.UseRazorComponentsRuntimeCompilation(IApplicationBuilder app)
at BServer....Startup.Configure(IApplicationBuilder app, IWebHostEnvironment env) in C:\Users......\Startup.cs:line 109
at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor, Boolean wrapExceptions)
at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
at Microsoft.AspNetCore.Hosting.ConfigureBuilder.Invoke(Object instance, IApplicationBuilder builder)
at Microsoft.AspNetCore.Hosting.ConfigureBuilder.<>c__DisplayClass4_0.b__0(IApplicationBuilder builder)
at Microsoft.AspNetCore.Hosting.GenericWebHostBuilder.<>c__DisplayClass13_0.b__2(IApplicationBuilder app)
at Microsoft.AspNetCore.Mvc.Filters.MiddlewareFilterBuilderStartupFilter.<>c__DisplayClass0_0.g__MiddlewareFilterBuilder|0(IApplicationBuilder builder)
at Microsoft.AspNetCore.Server.IIS.Core.IISServerSetupFilter.<>c__DisplayClass2_0.b__0(IApplicationBuilder app)
at Microsoft.AspNetCore.HostFilteringStartupFilter.<>c__DisplayClass0_0.b__0(IApplicationBuilder app)
at Microsoft.AspNetCore.Hosting.GenericWebHostService.d__31.MoveNext()

[Levvy055]

Having the same problem using Net5 Blazor Server.