using System.Runtime.InteropServices;

namespace WindowsFormsApplication1
{
    public partial class NativeMethods
    {
        /// <summary>
        /// 啟動控制臺
        /// </summary>
        /// <returns></returns>
        [DllImport("kernel32.dll")]
        public static extern bool AllocConsole();
        /// <summary>
        /// 釋放控制臺
        /// </summary>
        /// <returns></returns>
        [DllImport("kernel32.dll")]
        public static extern bool FreeConsole();
    }
}

using System;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    static class Program
    {
        /// <summary>
        /// 應用程序的主入口點。
        /// </summary>
        [STAThread]
        static void Main(string[] args)
        {
            try
            {
                if (args.Length > 0 && args[0].ToLower() == "-c")
                {//通過命令行 xxxx.exe -c 參數啟動，Console

                    //注意：不用 Main(string[] args)、System.Environment.GetCommandLineArgs();  也可以取得命令行參數在任何地方

                    //啟動
                    NativeMethods.AllocConsole();
                    Console.WriteLine("控制臺以啟動");
                }

                Application.EnableVisualStyles();
                Application.SetCompatibleTextRenderingDefault(false);
                Application.Run(new Form1());
            }
            finally
            {
                //關閉 （如果在這個位置其實寫不寫都行了）
                NativeMethods.FreeConsole();
            }
        }
    }
}

using System;
using System.Windows.Forms;
namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void btnOpenConsole_Click(object sender, EventArgs e)
        {
            //開啟控制臺
            NativeMethods.AllocConsole();
        }

        private void btnCloseConsole_Click(object sender, EventArgs e)
        {
            //關閉控制臺
            NativeMethods.FreeConsole();
        }

        private void btnOut_Click(object sender, EventArgs e)
        {
            //模擬輸出
            Console.WriteLine(textBox1.Text);
        }
    }
}