实现效果：

代码：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace NoBorderForm
{
  public partial class Form1 : Form
  {
    public Form1()
    {
      InitializeComponent();
    }
    
    private void Form1_Load(object sender, EventArgs e)
    {
      
    }

    Point mouseOff;//鼠标移动位置变量
    bool leftFlag;//标记是否为左键
    private void Form1_MouseDown(object sender, MouseEventArgs e)
    {
      if (e.Button == MouseButtons.Left)
      {
        mouseOff = new Point(-e.X, -e.Y); //得到变量的值
        leftFlag = true;         //点击左键按下时标注为true;
      }
    }

    private void Form1_MouseMove(object sender, MouseEventArgs e)
    {
      if (leftFlag)
      {
        Point mouseSet =【文章转自：中东服务器】 Control.MousePosition;
        mouseSet.Offset(mouseOff.X, mouseOff.Y); //设置移动后的位置
        Location = mouseSet;
      }
    }

    private void Form1_MouseUp(object sender, MouseEventArgs e)
    {
      if (leftFlag)
      {
        leftFlag = false;//释放鼠标后标注为false;
      }
    }

    private void button1_Click(object sender, EventArgs e)
    {
      DialogResult dr = MessageBox.Show("yes/no", "exit", MessageBoxButtons.YesNo, MessageBoxIcon.Warning);
      if (dr == DialogResult.Yes)
      {
        this.Close();
      }
      else
      {
        return;
      }
    }

    private void button2_Click(object sender, EventArgs e)
    {
      this.WindowState = FormWindowState.Minimized;
    }

    private void checkBox1_CheckedChanged(object sender, EventArgs e)
    {

    }

    private void Form1_Click(object sender, EventArgs e)
    {

    }

    private void panel1_Click(object sender, EventArgs e)
    {
      
    }

    private void textBox1_Click(object sender, EventArgs e)
    {
      
    }

    private void linkLabel1_LinkClicked(object sender, LinkLabelLinkClickedEventArgs e)
    {
      System.Diagnostics.Process.Start("http://www.baidu.com");
    }

    private void button4_Click(object sender, EventArgs e)
    {
      
    }
  }
}