什么是MVVM架构和数据绑定？

using HeYin.ERP.DataModels;using HeYin.ERP.IServices;using HeYin.ERP.Models;using HeYin.ERP.Services;using Microsoft.Practices.Prism.Commands;using System;using System.Collections.Generic;using System.Collections.ObjectModel;using System.Windows;using System.Text.RegularExpressions;using System.Windows.Controls;namespace HeYin.ERP.Client.ViewModels.Customer
{class CusGroupEditViewModel : BaseViewModel
    {private bool bIsAdd = false;

        ICusGroupService CGS;  //调用IService接口#region Properties 属性private Guid gCsGroupID = Guid.Empty;//All CusGroupprivate List csGroupsAll;public List CsGroupsAll
        {get { return csGroupsAll; }set{
                csGroupsAll = value; //设定值OnPropertyChanged("CsGroupsAll"); //在属性更改后，通知            }
        }private List csGroupsMinPrestore;public List CsGroupsAllMinPrestore
        {get { return csGroupsMinPrestore; }set{
                csGroupsMinPrestore = value; //设定值OnPropertyChanged("CsGroupsAllMinPrestore"); //在属性更改后，通知            }
        }//CusGroup对象private CusGroup csGroup;public CusGroup CsGroup
        {get { return csGroup; }set{ csGroup = value;
                OnPropertyChanged("CsGroup"); }
        }/// 
/// /// 
private string strCMBselectValue;public string StrCMBselectValue
        {get { return strCMBselectValue; }set{if (value != null)
                {
                    strCMBselectValue = value;
                    OnPropertyChanged("StrCMBselectValue");
                }
            }
        }/// 
/// ComboBoxDataModel：作为一个ComboBox的对象，可以理解为数据源/// 
private ObservableCollection lstCSGDownLevelID;public ObservableCollection LstCSGDownLevelID
        {get { return lstCSGDownLevelID; }set{
                lstCSGDownLevelID = value;
                OnPropertyChanged("LstCSGDownLevelID");
            }
        }//DataGrid当前选择对象private CusGroup currentSelectItem;public CusGroup CurrentSelectItem
        {get { return currentSelectItem; }set{
                currentSelectItem = value;

                GetCutCmbSelect(value);
            }
        }private int errorCount;public int ErrorCount { get => errorCount; set => errorCount = value; }#endregion#region Commandspublic DelegateCommand BtnChangedCommand { get; set; }public DelegateCommand TxtChangedCommand { get; set; }        #endregionpublic CusGroupEditViewModel()
        {
            CGS = new CusGroupService();
            CsGroupsAll = new List();
            csGroup = new CusGroup();
            LstCSGDownLevelID = new ObservableCollection();
            BtnChangedCommand = new DelegateCommand(MenuClick);
            TxtChangedCommand = new DelegateCommand(ChangeCMBValue);

            GetAllCusGroups();
        }#region ButtonClickprivate void MenuClick(string strMessage)
        {if (string.IsNullOrEmpty(strMessage)) return;if (CsGroup == null) return;switch (strMessage)
            {case "btnCusGroupSave":
                    Save();break;case "btnCusGroupAdd":
                    Add();break;case "btnCusGroupDelete":
                    Delete();break;
            }
        }#endregion ButtonClick#region motheds/// 
/// 获取全部Group/// 
private void GetAllCusGroups()
        {//获取满足条件的客户分组信息            CsGroupsAll.Clear();
            CsGroupsAll = CGS.Get(s => s.IsDelete == 0);

            GetAllCMBItems();//给降档分组下拉框赋值if ((gCsGroupID == null || gCsGroupID == Guid.Empty) && CsGroupsAll.Count > 0)
                CsGroup = CsGroupsAll[0];    //给基础信息等赋值StrCMBselectValue = CsGroup.DownLevelID.ToString();//设置降档分组默认值        }/// 
/// 添加/// 
/// private void AddCusGroup(CusGroup cg)
        {
            cg.ID = Guid.NewGuid(); //新建分组GUIDcg.IsDelete = 0;        //默认为0：不删除cg.CreateBy = App.GetCurrentUserId();//创建人员关联员工 GUIDcg.CreateTime = DateTime.Now;  //初始化创建时间，应该使用服务器当前时间bool c = CGS.Add(cg);if (c)
            {
                MessageBox.Show(string.Format("创建新组别【{0}】成功！", CsGroup.Name), "提示", MessageBoxButton.OK, MessageBoxImage.Information);
                GetAllCusGroups();
                bIsAdd = false;
            }
        }/// 
/// 修改/// 
/// private void UpdateCusGroup(CusGroup cg)
        {
            bIsAdd = false;

            cg.UpdateTime = DateTime.Now;
            cg.UpdateBy = App.GetCurrentUserId();//更新人员关联员工 GUIDstring[] str = { "UpdateTime", "UpdateBy" };bool b = CGS.Edit(cg, str);if (b)
            {
                MessageBox.Show("更改组别【成功】！", "提示", MessageBoxButton.OK, MessageBoxImage.Information);
                GetAllCusGroups();
            }
        }/// 
///删除方法（实为更新）/// 
/// private void DeleteCusGroup(CusGroup cg)
        {
            cg.IsDelete = 1; //更改数据库删除标志cg.UpdateTime = DateTime.Now;  //更新删除时间cg.UpdateBy = App.GetCurrentUserId();//更新人员关联员工 GUIDstring[] str = { "UpdateTime", "IsDelete", "UpdateBy" };bool b = CGS.Edit(cg, str);if (b)
            {//MessageBox.Show(string.Format("已删除组别【{0}】！", CsGroup.Name), "提示", MessageBoxButton.OK, MessageBoxImage.Information);                GetAllCusGroups();
                CsGroup = new CusGroup(); //清空对象bIsAdd = true;
            }
        }/// 
/// 插入和更新方法调用/// 
private void Save()
        {if (ErrorCount > 0)
            {//判断必填数据是否为空：为空则提示MessageBox.Show("请核对所填数据", "提示", MessageBoxButton.YesNo, MessageBoxImage.Information);return;
            }if (bIsAdd)
                AddCusGroup(CsGroup);elseUpdateCusGroup(CsGroup);
        }/// 
/// 获取降档分组下拉列表的值，并指定默认值/// 
/// private void GetCutCmbSelect(CusGroup value)
        {
            bIsAdd = false;//点击新增后，再选择列表的逻辑if (value != null)
            {
                CsGroup = CGS.GetById(value.ID);//查找出当前选中的对象gCsGroupID = CsGroup.ID;        //保存当前选择对象的GUIDif (CsGroup != null)
                {if (CsGroup.DownLevelID.HasValue)
                    {//如果降档ID有值，则默认显示，如果没有，则显示为空GetExceptCMBSelect();//刷新下拉列表，先刷新，再赋值给默认值StrCMBselectValue = CsGroup.DownLevelID.ToString();
                    }else{
                        LstCSGDownLevelID.Clear();
                        StrCMBselectValue = string.Empty;
                    }
                }
            }
        }private void Add()
        {
            bIsAdd = true;//点击新建分组时，重新获取所有降档ID对应的中文名            GetAllCMBItems();

            CsGroup = new CusGroup();
        }private void Delete()
        {if (this.CsGroup.ID == Guid.Empty || CsGroup.ID == null)
                MessageBox.Show("请选择要删除组别", "提示", MessageBoxButton.OK, MessageBoxImage.Information);else{
                MessageBoxResult msgResult = MessageBox.Show(string.Format("确定要删除分组【{0}】吗？", CsGroup.Name), "提示", MessageBoxButton.YesNo, MessageBoxImage.Information);if (msgResult == MessageBoxResult.Yes)
                    DeleteCusGroup(CsGroup);
            }
        }/// 
/// 排除当前列的降档ID和对应的Name/// 
private void GetExceptCMBSelect()
        {
            LstCSGDownLevelID.Clear();
            CsGroupsAllMinPrestore = CGS.Get(s => s.IsDelete == 0 && s.MinPrestore <= CsGroup.MinPrestore);foreach (var iDlID in CsGroupsAllMinPrestore)
            {if (iDlID.ID != CsGroup.ID) //去除当前选择ID对应的NameLstCSGDownLevelID.Add(new ComboBoxDataModel() { Value = iDlID.ID.ToString(), Text = iDlID.Name });
            }
        }/// 
/// 获取列表中所有降档ID和对应的Name/// 
private void GetAllCMBItems()
        {
            LstCSGDownLevelID.Clear();foreach (var iDlID in CsGroupsAll)
            {
                LstCSGDownLevelID.Add(new ComboBoxDataModel() { Value = iDlID.ID.ToString(), Text = iDlID.Name });
            }
        }private void ChangeCMBValue(CusGroup cgMinPrestore)
        {
            LstCSGDownLevelID.Clear();
            List lstTextChange = new List();
            lstTextChange = CGS.Get(s => s.MinPrestore