使用.net core 3.0 搭建的Web API接口，用另一个服务器访问时候报这个错误：
解决方法如下：
1、在web api 项目的startup类的ConfigureServices方法中加入以下内容。
/// <summary>
///
/// </summary>
/// <param name="services"></param>
// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
services.AddControllers();
//
services.AddCors(options =>
{
options.AddPolicy("AllowSpecificOrigins",
builder =>
{
builder.WithOrigins("http://localhost:56003").AllowAnyHeader();
});
});
}
2、在configure方法中加入以下内容，重新编译运行就可以了。
/// <summary>
///
/// </summary>
/// <param name="app"></param>
/// <param name="env"></param>
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
app.UseRouting();
app.UseCors("AllowSpecificOrigins");
app.UseStaticFiles();
app.UseAuthorization();
app.UseEndpoints(endpoints =>
{
endpoints.MapControllers();
});
}