How do you fix “The CORS protocol does not allow specifying a wildcard (any) origin and credentials at the same time” error in Blazor Server application?

In a Blazor Server application, if you want to use both AllowCredentials() and AllowAnyOrigin() with respect to CORS settings, then add SetIsOriginAllowed(Func<string,bool> predicate) under ConfigureServices in the Startup.cs file instead of using AllowAnyOrigin(). See the following code snippet. 

[Startup.cs] 

public void ConfigureServices(IServiceCollection services) 

{ 

        …… 

        …… 

        services.AddCors(options => 

        { 

        options.AddPolicy("Open", builder => 

        builder.SetIsOriginAllowed(_ => true). 

        AllowAnyMethod(). 

        AllowAnyHeader(). 

        AllowCredentials()); 

    }); 

} 

Refer to this link for more information.