POJO:
class ComboBoxItem
{
string _text;
string _value;

public string Text
{
get { return _text; }
set { _text = value; }
}


public string Value
{
get { return _value; }
set { _value = value; }
}
public override String ToString() {
return this.Value;
}

}
Init:
private void SurferWithProxy_Load(object sender, EventArgs e)
{
intiComboBox();
}


private void intiComboBox() {
ComboBoxItem cbi = new ComboBoxItem();
cbi = new ComboBoxItem();
cbi.Text = "test1";
cbi.Value = "Value1";
this.cboURL.Items.Add(cbi);

cbi = new ComboBoxItem();
cbi.Text = "test2";
cbi.Value = "Value2";
this.cboURL.Items.Add(cbi);

cbi = new ComboBoxItem();
cbi.Text = "test3";
cbi.Value = "Value3";
this.cboURL.Items.Add(cbi);

cbi = new ComboBoxItem();
cbi.Text = "test4";
cbi.Value = "Value4";
this.cboURL.Items.Add(cbi);

this.cboURL.DisplayMember = "Text";
this.cboURL.ValueMember = "Value";
}
Click:  
private void btnStart_Click(object sender, EventArgs e)
{
string url = ((ComboBoxItem)this.cboURL.SelectedItem).Value;
MessageBox.Show(url);
}

补充:

ComboBox控件添加项有两种方法:

一、编程方式添加:

使用comboBox.Items.Add(ojbect item)方法添加一个项

private void DoBindData()
{
for (int

二、进行数据源绑定:

private void DoBindDataSource()
{
//构造数据源(或从数据库中查询)
DataTable ADt = new DataTable();
DataColumn ADC1 = new DataColumn("F_ID", typeof(int));
DataColumn ADC2 = new DataColumn("F_Name", typeof(string));
ADt.Columns.Add(ADC1);
ADt.Columns.Add(ADC2);
for (int i = 0; i < 3; i++)
{
DataRow ADR = ADt.NewRow();
ADR[0] = i+1;
ADR[1] = "Name_" + (i+1);
ADt.Rows.Add(ADR);
}
//进行绑定
comboBox1.DisplayMember = "F_Name";//控件显示的列名
comboBox1.ValueMember = "F_ID";//控件值的列名

三、其他操作和常用属性:

1)Text属性:获取当前显示的文本

2)SelectedText属性:获得当前选中的文本(控件获得光标且DropDown属性不为DropDownList)

                     注意:但应注意,所选内容会因用户交互而自动更改。如Button的Click事件中,SelectedIndexChanged 或 SelectedValueChanged 事件中,此属性会返回空字符串(参见MSCN:​​http://msdn.microsoft.com/zh-cn/partners/system.windows.forms.combobox.selectedtext(VS.90).aspx​​ )

3)SelectedValue属性:当前显示项对应的Value值(仅在绑定数据源时,设置了ValueMember时才可以用)

4)SelectedItem属性:控件当前选中项

5)SelectedIndex属性:当前选中项的索引

​http://rsljdkt.iteye.com/blog/826941​