//窗体1的代码
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 WindowsFormsApplication1
{
  public partial class Form1 : Form
  {
    public Form1()
    {
      InitializeComponent();
    }
     
    private void button1_Click(object sender, EventArgs e)
    {
      sharedclass.sharedvalue = textBox1.Text.ToString(); //静态变量的用法：类名.变量名 赋值给静态变量
      Form2 frm2 = new Form2();
      frm2.Show();     
    }
  }
  public static class sharedclass //在命名空间设置一个静态类sharedclass，不要放置在form1前面
  {
    public static string sharedvalue; //设置一个静态变量sharedvalue
  }
}

//窗体2的代码
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 WindowsFormsApplication1
{
  public partial class Form2 : Form
  {
    public Form2()
    {
      InitializeComponent();
      textBox1.Text = sharedclass.sharedvalue; //静态变量传入给窗口2的textBox
    }
  }
}