楼主的方法好像比较复杂
我在机子上试了半个小时也没出来

现在的方法比较简单
是网上学来的
并非和楼主一样的原创
我贴出来和大家一起分享

//在Form1 中
private void button1_Click ( object sender , System.EventArgs e )
{
Form2 myForm = new Form2 ( textBox1.Text , textBox2.Text ) ;
myForm.Show ( ) ;
}


//在Form2 中
public string str1, str2; //定义两个变量

public Form2(string sendData01, string sendData02) // 把“string sendData01, string sendData02” 添加到括号中去
{

InitializeComponent();
str1 = sendData01; //增加这两句
str2 = sendData02;
}


str1 和 str2 就可以直接使用了。

要不断的学习!

楼上的兄弟发贴好积极哦
对
要不断的学习

我今天准备下，明天贴出示例代码．
还有就是２１楼的兄弟，你用的方法只适合引用类型，如果是值类型就不好使了．

怎么没上传上来呢,那就把代码贴上来吧.
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;

namespace TransData
{
/// <summary>
/// Form1 的摘要说明。
/// </summary>
public class Form1 : System.Windows.Forms.Form
{
private System.Windows.Forms.Label label1;
private System.Windows.Forms.Label label2;
private System.Windows.Forms.NumericUpDown numericUpDown1;
private 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 窗体设计器生成的代码
/// <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.label1 = new System.Windows.Forms.Label();
this.label2 = new System.Windows.Forms.Label();
this.numericUpDown1 = new System.Windows.Forms.NumericUpDown();
this.textBox1 = new System.Windows.Forms.TextBox();
this.button1 = new System.Windows.Forms.Button();
((System.ComponentModel.ISupportInitialize)(this.numericUpDown1)).BeginInit();
this.SuspendLayout();
//
// label1
//
this.label1.Location = new System.Drawing.Point(40, 56);
this.label1.Name = "label1";
this.label1.TabIndex = 0;
this.label1.Text = "数据参数";
this.label1.TextAlign = System.Drawing.ContentAlignment.MiddleRight;
//
// label2
//
this.label2.Location = new System.Drawing.Point(40, 88);
this.label2.Name = "label2";
this.label2.TabIndex = 1;
this.label2.Text = "字符参数";
this.label2.TextAlign = System.Drawing.ContentAlignment.MiddleRight;
//
// numericUpDown1
//
this.numericUpDown1.Location = new System.Drawing.Point(152, 56);
this.numericUpDown1.Name = "numericUpDown1";
this.numericUpDown1.TabIndex = 2;
//
// textBox1
//
this.textBox1.Location = new System.Drawing.Point(152, 88);
this.textBox1.Name = "textBox1";
this.textBox1.Size = new System.Drawing.Size(120, 21);
this.textBox1.TabIndex = 3;
this.textBox1.Text = "";
//
// button1
//
this.button1.Location = new System.Drawing.Point(88, 160);
this.button1.Name = "button1";
this.button1.TabIndex = 4;
this.button1.Text = "打开新窗口";
this.button1.Click += new System.EventHandler(this.button1_Click);
//
// Form1
//
this.AutoScaleBaseSize = new System.Drawing.Size(6, 14);
this.ClientSize = new System.Drawing.Size(336, 309);
this.Controls.Add(this.button1);
this.Controls.Add(this.textBox1);
this.Controls.Add(this.numericUpDown1);
this.Controls.Add(this.label2);
this.Controls.Add(this.label1);
this.Name = "Form1";
this.Text = "Form1";
((System.ComponentModel.ISupportInitialize)(this.numericUpDown1)).EndInit();
this.ResumeLayout(false);

}
#endregion

/// <summary>
/// 应用程序的主入口点。
/// </summary>
[STAThread]
static void Main()
{
Application.Run(new Form1());
}

private void button1_Click(object sender, System.EventArgs e)
{
Form2 frm=new Form2((int)this.numericUpDown1.Value,this.textBox1.Text);//使用已经重载的窗体构造函数
frm.OnTranData+=new TranDataEventHandler(frm_OnTranData);//使用事件
frm.Show();
}

private void frm_OnTranData(object sender, TranDataEventArgs e)
{
//在事件处理函数中使用回传的数据
this.numericUpDown1.Value=e.IntData;
this.textBox1.Text=e.StrData;
}
}
}