c# a窗体调用b窗体里的东西

这个方法可能不是最好的,但是至少在功能上满足了你的要求,这里要注意的是:
Form1中的comboBox1的modifiers属性应该设置为:public
Form1窗体代码:

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

namespace windows
{
public partial class Form1 : Form
{
Form2 myForm2 = new Form2();
public Form1()
{
InitializeComponent();
myForm2.myForm1 = this;
myForm2.Show();
}

private void button1_Click(object sender, EventArgs e)
{
if (myForm2.Visible == false)
{
myForm2.Show();
}
else
{
myForm2.Hide();
}
}
}
}

Form2窗体代码:

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

namespace windows
{
public partial class Form2 : Form
{
public Form2()
{
InitializeComponent();
}

public Form1 myForm1;
private void button1_Click(object sender, EventArgs e)
{
if (!this.textBox1.Text.Equals(""))
{
myForm1.comboBox1.Items.Add(this.textBox1.Text.ToString());
}
}
}
}