Why I am i getting strict-origin-when-cross-origin when calling wep api from angualr?

Daer Developers,

I have .net core web api, and I have angualr client.

Now I am trying to call the web api from angualr ?

Here is my web api programme class ?

public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddCors();
            services.AddCors(o => o.AddPolicy("MyPolicy", builder =>
            {
                builder.WithOrigins("http://localhost:4200")
                       .AllowAnyMethod()
                       .AllowAnyHeader();
            }));


            services.AddCors(options =>
            {
                options.AddPolicy(name: "AllowOrigin", bulider =>
                {

                    bulider.WithOrigins("http://localhost:4200").AllowAnyHeader().AllowAnyMethod();
                });
            });
            services.AddDbContext<UserContext>(options => options.UseSqlServer(Configuration.GetConnectionString("MyDBConnection")));
            services.AddSwaggerGen(c =>
            {
                c.SwaggerDoc("v1", new OpenApiInfo 
                {
                    Title = "My API", 
                    Version = "v1" 
                });
            });
            services.AddControllers();
            services.AddCors();
            services.AddCors(c =>
            {
                c.AddPolicy("AllowOrigin", options => options.AllowAnyOrigin());
            });

            services.AddCors(options =>
            {
                options.AddPolicy(
                  "CorsPolicy",
                  builder => builder.WithOrigins("http://localhost:4200")
                  .AllowAnyMethod()
                  .AllowAnyHeader()
                  .AllowCredentials());
            });
            services.AddAuthentication(IISDefaults.AuthenticationScheme);

        }

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            app.UseHttpsRedirection();
            app.UseCors("CorsPolicy");

            app.UseRouting();
            app.UseCors(options =>options.WithOrigins("http://localhost:4200")
            .AllowAnyHeader()
            .AllowAnyMethod());
            app.UseSwagger();
            app.UseSwaggerUI();
            app.UseAuthorization();
            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
            });
        }
    }

Here is my angualr project api call.

 const options = 
    {headers: 
      {'Content-Type': 'application/json',"Access-Control-Allow-Origin":"*"}, 
    };
    this.http.post<null>("http://localhost:55768/api/CreateUser",
    JSON.stringify({FirstName: User.FirstName,
      LastName: User.LastName,
      Email: User.Email,
      Mobile: User.Mobile,
      Gender: User.Gender,
      Pwd: User.Pwd}), options).subscribe(
        (t: null) => console.info(JSON.stringify(t))
    );