通过事件，在两窗体间传递数据。

//---------------------------------------
// form1.cs
//----------------------------------------
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;

namespace FormConmunicate
{
    /// <summary>
    /// Form1 的摘要说明。
    /// </summary>

    public delegate string getText();

    public class Form1 : System.Windows.Forms.Form
    {
        public  System.Windows.Forms.TextBox textBox1;
        private System.Windows.Forms.Button button1;
        /// <summary>
        /// 必需的设计器变量。
        /// </summary>
        private System.ComponentModel.Container components = null;

        public Form1()
        {
            //
            // Windows 窗体设计器支持所必需的
            //
            InitializeComponent();

            //
            // TODO: 在 InitializeComponent 调用后添加任何构造函数代码
            //
        }

        /// <summary>
        /// 清理所有正在使用的资源。
        /// </summary>
        protected override void Dispose( bool disposing )
        {
            if( disposing )
            {
                if (components != null)
                {
                    components.Dispose();
                }
            }
            base.Dispose( disposing );
        }

        #region Windows Form Designer generated code
        /// <summary>
        /// 设计器支持所需的方法 - 不要使用代码编辑器修改
        /// 此方法的内容。
        /// </summary>
        private void InitializeComponent()
        {
            this.textBox1 = new System.Windows.Forms.TextBox();
            this.button1 = new System.Windows.Forms.Button();
            this.SuspendLayout();
            //
            // textBox1
            //
            this.textBox1.Location = new System.Drawing.Point(64, 40);
            this.textBox1.Name = "textBox1";
            this.textBox1.Size = new System.Drawing.Size(88, 21);
            this.textBox1.TabIndex = 0;
            this.textBox1.Text = "textBox1";
            //
            // button1
            //
            this.button1.Location = new System.Drawing.Point(104, 168);
            this.button1.Name = "button1";
            this.button1.Size = new System.Drawing.Size(96, 24);
            this.button1.TabIndex = 1;
            this.button1.Text = "button1";
            //this.button1.Click += new System.EventHandler(this.button1_Click);
            //
            // Form1
            //
            this.AutoScaleBaseSize = new System.Drawing.Size(6, 14);
            this.ClientSize = new System.Drawing.Size(292, 273);
            this.Controls.AddRange(new System.Windows.Forms.Control[] {
                                                                          this.button1,
                                                                          this.textBox1});


            FormHandel.myFormHandel[0]=(int)this.Handle;

            

            
            this.Name = "Form1";
            this.Text = "Form1";
            this.ResumeLayout(false);

        }
        #endregion

        /// <summary>
        /// 应用程序的主入口点。
        /// </summary>
        [STAThread]
        static void Main()
        {
            Form1 f1=new Form1();
            Form2 f2=new Form2();

            f2.TextChange+=new TextChangeEventHander(f1.ontextchange);
            
            f2.Show();

            Application.Run(f1);
        }

        private void ontextchange(object sender,Form2EventArg e)
        {
            this.textBox1.Text=e.MyText ;

        }
    }

    public class FormHandel
    {
        public static int[] myFormHandel={1,2};

    }

}

//-----------------------------------------------
// form2.cs
//-----------------------------------------------
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;

namespace FormConmunicate
{
    /// <summary>
    /// Form2 的摘要说明。
    /// </summary>
    ///
    
    public delegate void TextChangeEventHander(object sender,Form2EventArg e);

    public class Form2 : System.Windows.Forms.Form
    {
        public System.Windows.Forms.TextBox textBox1;
        private System.Windows.Forms.Button button1;

        public event TextChangeEventHander TextChange;
        
        /// <summary>
        /// 必需的设计器变量。
        /// </summary>
        private System.ComponentModel.Container components = null;


        public Form2()
        {
            //
            // Windows 窗体设计器支持所必需的
            //
            InitializeComponent();

            this.textBox1.Text=this.Handle.ToString();

            //
            // TODO: 在 InitializeComponent 调用后添加任何构造函数代码
            //
        }

        /// <summary>
        /// 清理所有正在使用的资源。
        /// </summary>
        protected override void Dispose( bool disposing )
        {
            if( disposing )
            {
                if(components != null)
                {
                    components.Dispose();
                }
            }
            base.Dispose( disposing );
        }

        #region Windows Form Designer generated code
        /// <summary>
        /// 设计器支持所需的方法 - 不要使用代码编辑器修改
        /// 此方法的内容。
        /// </summary>
        private void InitializeComponent()
        {
            this.textBox1 = new System.Windows.Forms.TextBox();
            this.button1 = new System.Windows.Forms.Button();
            this.SuspendLayout();
            //
            // textBox1
            //
            this.textBox1.Location = new System.Drawing.Point(168, 56);
            this.textBox1.Name = "textBox1";
            this.textBox1.Size = new System.Drawing.Size(80, 21);
            this.textBox1.TabIndex = 0;
            this.textBox1.Text = "textBox1";
            //
            // button1
            //
            this.button1.Location = new System.Drawing.Point(168, 136);
            this.button1.Name = "button1";
            this.button1.Size = new System.Drawing.Size(88, 24);
            this.button1.TabIndex = 1;
            this.button1.Text = "button1";
            this.button1.Click += new System.EventHandler(this.button1_Click);
            //
            // Form2
            //
            this.AutoScaleBaseSize = new System.Drawing.Size(6, 14);
            this.ClientSize = new System.Drawing.Size(292, 273);
            this.Controls.AddRange(new System.Windows.Forms.Control[] {
                                                                          this.button1,
                                                                          this.textBox1});

            FormHandel.myFormHandel[1]=(int)this.Handle;
            this.Name = "Form2";
            this.Text = "Form2";
            this.ResumeLayout(false);

        }
        #endregion

        private void button1_Click(object sender, System.EventArgs e)
        {

            //引发事件，并传递数据
            TextChange(this,new Form2EventArg(this.textBox1.Text));
        }
    }

    //事件数据
    public class Form2EventArg:System.EventArgs
    {
        private readonly string mytext ;

        public Form2EventArg(string str)
        {
            mytext=str;
        }

        public string MyText
        {
            get
            {
                return mytext;
            }

        }
    }

}

原文转自：http://www.ltesting.net