using System;
using System.Collections.Generic;
using
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

namespace WindowsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            static void Main()
            {
                Application.Run(new Form1());
            }

        private void button1_Click(object sender, EventArgs e)
        {
            long op1,op2,result;
            if ((textBox1.Text =="")||(textBox2.Text ==""))
            {
                MessageBox.Show(this,"null","msg",MessageBoxButtons.OK ,
                     MessageBoxIcon.Information );
                return;
            }
            try
            {
                op1=Convert.ToInt64(textBox1.Text );
                op2=Convert.ToInt64(textBox2.Text );
                result=op1+op2;
                rextBox3.Text=Convert.ToString (result );
            }
            catch(Exception e1)
            {
                MessageBox.Show
                (this,e1.Message ,"msg",MessageBoxButtons.OK,MessageBoxIcon.Warning );
            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            this.Close();
        }
        }
    }
}

总是提示缺少调试目标，无法开始调试！

不是很理解你们是什么意思，不过我把
private void Form1_Load(object sender, EventArgs e)
        {
            static void Main()
            {
                Application.Run(new Form1());
            }

去掉之后就好了！谢谢各位！