[.net自定义控件]ComboBox控件重写 之ComboBoxEx

using System;
using System.Windows.Forms;
//web:http://www.yongfa365.com/
namespace YongFa365.Controls.ComboBoxEx
{
    public partial class ComboBoxEx : ComboBox
    {
        public ComboBoxEx()
        {
            this.DropDownStyle = ComboBoxStyle.DropDownList;
        }

        public void SelectedByValue(object obj)
        {
            if (this.DataSource == null)
            {
                //非绑定时
                this.SelectedItem = obj;
            }
            else
            {
                object preValue = this.SelectedValue;
                //绑定时直接查找
                this.SelectedValue = obj;
                if (this.SelectedValue == null)
                {
                    //查不到保持原控件值不变
                    this.SelectedValue = preValue;
                }
            }
        }

        public void SelectedByText(object obj)
        {
            if (this.DataSource == null)
            {
                //非绑定时
                this.SelectedItem = obj;
            }
            else
            {
                //绑定时
                this.Text = obj.ToString();
            }
        }

        public string Value
        {
            get
            {
                if (this.DataSource == null)
                {
                    //非绑定时返回Text
                    return this.Text;
                }
                else
                {
                    //绑定时返回SelectedValue
                    return this.SelectedValue.ToString();
                }
            }
        }
    }
}