如果是自定义的header名称，须要在跨域中设置：.WithExposedHeaders(“X-Total-Count”)

      services.AddCors(options =>
      {
        options.AddPolicy("AllowAllOrigin", builder =>
              {
                builder
                      .AllowAnyOrigin()
                      .AllowAnyHeader()
                      .AllowAnyMethod()
                      .AllowCredentials()
                      .WithExposedHeaders("X-Total-Count")
                      .WithExposedHeaders("X-Pagination");
              });
      });