using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using System.Windows.Forms;

namespace WindowsFormsApplication1

{

    class MultiFormApplictionStart : ApplicationContext

    {

        /// <summary>

        /// 多窗口同时启动类

        /// <remarks>继承ApplicationContext的原因是Application.Run(ApplicationContext context);参数的需要</remarks>

        /// <remarks>另一个是关闭同时启动的窗口</remarks>

        /// </summary>

        private void onFormClosed(object sender, EventArgs e)

        {

            if (Application.OpenForms.Count == )

            {

                ExitThread();

            }

        }

        public MultiFormApplictionStart()

        {

            //将要显示的窗体集合

            var formList = new List<Form>(){

                new Form1(),

                new Form2()

            };

            foreach (var item in formList)

            {

                item.FormClosed += onFormClosed;

            }

            foreach (var item in formList)

            {

                item.Show();

            }

        }

    }

}

using System;

using System.Collections.Generic;

using System.Linq;

using System.Windows.Forms;

namespace WindowsFormsApplication1

{

    static class Program

    {

        /// <summary>

        /// 应用程序的主入口点。

        /// </summary>

        [STAThread]

        static void Main()

        {

            Application.EnableVisualStyles();

            Application.SetCompatibleTextRenderingDefault(false);

            Application.Run(new MultiFormApplictionStart());    //调用用于显示窗体的类

        }

    }

}