C# Combobox

using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Windows.Forms;

namespace KK.Control.Helper
{
    public class CmbHelper
    {
        //定义一个用于保存静态变量的实例
        private static CmbHelper instance = null;
        //定义一个保证线程同步的标识
        private static readonly object locker = new object();
        //构造函数为私有，使外界不能创建该类的实例
        private CmbHelper() { }
        public static CmbHelper Instance
        {
            get
            {
                if (instance == null)
                {
                    lock (locker)
                    {
                        if (instance == null) instance = new CmbHelper();
                    }
                }
                return instance;
            }
        }

        public TModel GetTModel<TModel>(ComboBox cmb)
        {
            //ZB.QueueSys.Model.QS_QUEUE queue = this.cmbQueue.SelectedItem as ZB.QueueSys.Model.QS_QUEUE;
            //StudentInfos stu = CmbHelper.Instance.GetTModel<StudentInfos>(this.cmbTest);
            return (TModel)cmb.SelectedItem;
        }

        public void BindingCmb<TModel>(List<TModel> list, ComboBox cmb, string displayMember)
        {
            if (list == null || list.Count <= 0)
            {
                cmb.DataSource = null;
                return;
            }
            cmb.DataSource = list;
            cmb.DisplayMember = displayMember;
            cmb.SelectedIndex = 0;
            //List<V_APPLYDEPART> departs = AppDepartBLL.GetApplyDeparts();
            //if (departs != null && departs.Count > 0) departs.Insert(0, new V_APPLYDEPART { APPLYDEPART = PubVariable.All, DEPARTID = "-1" });
            //PubHelper.Instance.BindingCmb(departs, this.cmbDepart, "APPLYDEPART");
        }

        public void BindingCmbAndInsetAll<TModel>(List<TModel> list, ComboBox cmb, string displayMember, string all = "全部")
        {
            if (list == null || list.Count <= 0)
            {
                cmb.DataSource = null;
                return;
            }
            cmb.Items.Clear();
            cmb.Items.Add(all);
            foreach (TModel item in list)
            {
                cmb.Items.Add(item);
            }
            //cmb.DataSource = list;
            cmb.DisplayMember = displayMember;
            cmb.SelectedIndex = 0;
            //PubHelper.Instance.BindingCmb(departs, this.cmbDepart, "APPLYDEPART");
        }

        /// <summary>
        /// 为ComboBox绑定数据源并提供下拉提示
        /// </summary>
        /// <typeparam name="T">泛型</typeparam>
        /// <param name="combox">ComboBox</param>
        /// <param name="list">数据源</param>
        /// <param name="displayMember">显示字段</param>
        /// <param name="valueMember">隐式字段</param>
        /// <param name="displayText">下拉提示文字</param>
        public void Bind<T>(ComboBox combox, IList<T> list, string displayMember, string valueMember, string displayText = "全部")
        {
            AddItem(list, displayMember, displayText);
            combox.DataSource = list;
            combox.DisplayMember = displayMember;
            if (!string.IsNullOrEmpty(valueMember))
                combox.ValueMember = valueMember;
        }

        private void AddItem<T>(IList<T> list, string displayMember, string displayText)
        {
            Object _obj = Activator.CreateInstance<T>();
            Type _type = _obj.GetType();
            if (!string.IsNullOrEmpty(displayMember))
            {
                PropertyInfo _displayProperty = _type.GetProperty(displayMember);
                _displayProperty.SetValue(_obj, displayText, null);
            }
            list.Insert(0, (T)_obj);
        }


    }
}