【MVVM Dev】多个具有依赖性质的ComboBox对数据的过滤

一、前言

       在界面编程中，我们常常会遇到具有依赖性质的ComboBox框，比如最常见的：

       省/直辖市 => 地级市/区 => 区/街道

       今天就说一下在WPF的MVVM模式中如何实现该功能

二、范例

      假设有一段原始数据，名为：TotalData

       其包含四个可以过滤的属性：AType、BType、CType、DType

       与其对应的有四个ComboBox：

       1. SelectedItem绑定：ATypeSelected   ItemsSource绑定为：ATypes

       2. SelectedItem绑定：BTypeSelected   ItemsSource绑定为：BTypes

       3. SelectedItem绑定：CTypeSelected   ItemsSource绑定为：CTypes

       4. SelectedItem绑定：DTypeSelected   ItemsSource绑定为：DTypes

class Temp
{
        private string _ATypeSelected;
        public string ATypeSelected
        {
            get
            {
                return _ATypeSelected;
            }
            set
            {
                if (SetProperty(ref _ATypeSelected, value, () => ATypeSelected))
                {
                    BTypes.Clear();
                    var BTempTypes = new List<string>();

                    if (ATypeSelected != "全部A类型" && ATypeSelected != null)
                    {
                        BTempTypes.AddRange(TotalData.Where(x => x.AType == ATypeSelected).Select(item => item.BType));
                    }
                    else
                    {
                        BTempTypes.AddRange(TotalData.Select(item => item.BType));
                    }


                    BTypes.Add("全部B类型");
                    foreach (var item in BTempTypes.Distinct())
                    {
                        BTypes.Add(item);
                    }
                    BTypeSelected = BTypes[0];
                }
            }
        }


        private string _BTypeSelected;
        public string BTypeSelected
        {
            get
            {
                return _BTypeSelected;
            }
            set
            {
                if (SetProperty(ref _BTypeSelected, value, () => BTypeSelected))
                {
                    CTypes.Clear();
                    var CTempTypes = new List<string>();

                    if (ATypeSelected != "全部A类型" && ATypeSelected != null)
                    {
                        if (BTypeSelected != "全部B类型" && BTypeSelected != null)
                        {
                            CTempTypes.AddRange(from item in TotalData where item.AType == ATypeSelected && item.BType == BTypeSelected select item.CType);
                        }
                        else if (BTypeSelected == "全部B类型")
                        {
                            CTempTypes.AddRange(from item in TotalData where item.AType == ATypeSelected select item.CType);
                        }
                    }
                    else
                    {
                        if (BTypeSelected != "全部B类型" && BTypeSelected != null)
                        {
                            CTempTypes.AddRange(from item in TotalData where item.BType == BTypeSelected select  item.CType);
                        }
                        else if (BTypeSelected == "全部B类型")
                        {
                            CTempTypes.AddRange(TotalData.Select(item => item.CType));
                        }
                    }
                    CTypes.Add("全部C类型");
                    foreach (var item in CTempTypes.Distinct())
                    {
                        CTypes.Add(item);
                    }
                    CTypeSelected = CTypes[0];
                }
            }
        }



        private string _CTypeSelected;
        public string CTypeSelected
        {
            get
            {
                return _CTypeSelected;
            }
            set
            {
                if (SetProperty(ref _CTypeSelected, value, () => CTypeSelected))
                {
                    DTypes.Clear();
                    var DTempTypes = new List<string>();

                    if (ATypeSelected != "全部A类型" && ATypeSelected != null)
                    {
                        if (BTypeSelected != "全部B类型" && BTypeSelected != null)
                        {
                            if (CTypeSelected != null && CTypeSelected != "全部C类型")
                            {
                                DTempTypes.AddRange(from item in TotalData where item.BType == BTypeSelected && item.CType == CTypeSelected && item.AType == ATypeSelected  select item.DType);
                            }
                            else if (CTypeSelected == "全部C类型")
                            {
                                DTempTypes.AddRange(from item in TotalData where item.BType == BTypeSelected && item.AType == ATypeSelected select item.DType);
                            }

                        }
                        else if (BTypeSelected == "全部B类型")
                        {
                            if (CTypeSelected != null && CTypeSelected != "全部C类型")
                            {
                                DTempTypes.AddRange(from item in TotalData where item.CType == CTypeSelected && item.AType == ATypeSelected select item.DType);
                            }
                            else if (CTypeSelected == "全部C类型")
                            {
                                DTempTypes.AddRange(from item in TotalData where item.AType == ATypeSelected select item.DType);
                            }
                        }
                    }
                    else
                    {
                        if (BTypeSelected != "全部B类型" && BTypeSelected != null)
                        {
                            if (CTypeSelected != null && CTypeSelected != "全部C类型")
                            {
                                DTempTypes.AddRange(from item in TotalData where item.BType== BTypeSelected && item.CType == CTypeSelected select item.DType);
                            }
                            else if (CTypeSelected == "全部C类型")
                            {
                                DTempTypes.AddRange(from item in TotalData where item.BType == BTypeSelected select item.DType);
                            }

                        }
                        else if (BTypeSelected == "全部B类型")
                        {
                            if (CTypeSelected != null && CTypeSelected != "全部C类型")
                            {
                                DTempTypes.AddRange(from item in TotalData where item.CType == CTypeSelected select item.DType);
                            }
                            else if (CTypeSelected == "全部C类型")
                            {
                                DTempTypes.AddRange(TotalData.Select(item => item.DType));
                            }
                        }
                    }
                    
                    
                    DTypes.Add("全部D类型");
                    foreach (var item in DTempTypes.Distinct())
                    {
                        DTypes.Add(item);
                    }
                    DTypeSelected = DTypes[0];
                }
            }
        }


        private string _DTypeSelected;

        public string DTypeSelected
        {
            get { return _DTypeSelected; }
            set
            {
                SetProperty(ref _DTypeSelected, value, () => DTypeSelected); 
                
                //在此处可以根据上述的ATypeSelected、BTypeSelected、CTypeSelected、DTypeSelected 对 TotalData 进行过滤从而得到想要显示在界面上的数据列表

            }
        }



}