.Net平台Winform两个ComboBox控件绑定同一个数据源

今天WINFROM编程遇到这么一个问题：是有关WINFORM中两个comboBox控件绑定同一个数据源的问题，在窗体的界面上有两个comboBox，我在Form1_Load中对他们做了数据绑定（具体代码如下），但是运行出现了这个一个奇怪的问题，我改变了comboBox1的值，但是comboBox2的值也自动改变了，我没有设置comboBox1_SelectedIndexChanged函数

 private void Form1_Load(object sender, EventArgs e)
 {
 dataset ds=getds("select code,name from shp") ;

 comboBox1.DataSource = ds;
 comboBox1.ValueMember = "code";
 comboBox1.DisplayMember = "name";
 comboBox1.SelectedIndex = ; 

 comboBox2.DataSource = ds;
 comboBox2.ValueMember = "code";
 comboBox2.DisplayMember = "name";
 comboBox2.SelectedIndex = ;
 }

解决方法：

 dataset ds=getds("select code,name from shp") 

 comboBox1.DataSource = ds;
 comboBox1.ValueMember = "code";
 comboBox1.DisplayMember = "name";
 comboBox1.SelectedIndex = ; 

 comboBox2.DataSource = ds.Copy();
 comboBox2.ValueMember = "code";
 comboBox2.DisplayMember = "name";
 comboBox2.SelectedIndex = ;