c#所有部门及其下所部门生成树形图（递归算法获取或键值对方式获取）

第一种解决方案（递归）：

//生成树的方法
        public List<JieDian> creatTree()
        {
            List<JieDian> result = new List<JieDian>();
            try
            {
               string sql = string.Format(@"SELECT a.Name [DepartName],a.Id [DepartId]
FROM [HYSYZSCCODB].[dbo].[Department] a
where  a.IsValid='true' and a.Level = 1");
                    //这里改成你的数据库表
                    var data = container.Database.SqlQuery<DepartDTO>(sql).ToList(); //这里我直接调用了我库中的类
                    foreach (var item in data)
                    {
                        JieDian jd = new JieDian();
                        jd.Id = item.DepartId;
                        jd.Name = item.DepartName;
                        var d = creatTheTree(item.DepartId, jd);
                        if (d == null)
                        {
                            result.Add(jd);
                            continue;
                        }
                        result.Add(d);
                    }
            }
            catch (Exception e)
            {
                throw e;
            }
            return result;
        }

        //生成树的方法(自身方法不断循环)
        public JieDian creatTheTree(Guid parentId, JieDian jd)
        {
            //获取
            DepartDTO[] items = GetTheItems(parentId);
            //如果没有字节点了，那就返回空
            if (items.Length == 0)
                return null;
            List<JieDian> jdList = new List<JieDian>();
            for (int i = 0; i < items.Length; i++)
            {
                JieDian jiedian = new JieDian();
                jiedian.Id = items[i].DepartId;
                jiedian.Name = items[i].DepartName;
                jiedian.ParentId = items[i].ParentId;
                //递归循环
                creatTheTree(items[i].DepartId, jiedian);
                jdList.Add(jiedian);
            }
            jd.children = jdList.ToArray(); //由于对象是引用类型，因为可以改变参数的值
            return jd;
        }


 public class JieDian
    {
        /// <summary>
        /// 
        /// </summary>
        public string Name { get; set; }
        /// <summary>
        /// 
        /// </summary>
        public Guid Id { get; set; }
        /// <summary>
        /// 
        /// </summary>
        public Guid ParentId { get; set; }
        /// <summary>
        /// 
        /// </summary>
        public JieDian[] children = null;
    }

第二种解决方案（key-Value）：

#region  尝试不用递归生成树（更简洁高效）  
        public class ResChapter
        {
            public string Id { get; set; }
            public string Name { get; set; }
            public string Pid { get; set; }
            public List<ResChapter> Children { get; set; }
        }

        public List<ResChapter> toTree()
        {       //数据库中的Id和父级Id都是Guid类型，取出的时候转为string类型，而第一级部门PDepartmentId为空，我们用isnull(cast(a.Id as varchar(40)),'')进行处理，如果为空就返回空字符串，否则就把guid转为字符串取出来。
//cast(a.Id as varchar(40))      -----将id转为字符串的操作
                string sql = string.Format(@"SELECT a.Name [Name],isnull(cast(a.Id as varchar(40)),'') [Id],isnull(cast(a.PDepartmentId as varchar(40)),'') [Pid]
FROM [HYSYZSCCODB].[dbo].[Department] a
where  a.IsValid='true' ");
                //这里改成你的数据库表
                var data = container.Database.SqlQuery<ResChapter>(sql).ToList(); //这里我直接调用了我库中的类
                var chapterlist = data;
                var dic = new Dictionary<string, ResChapter>(chapterlist.Count);
                foreach (var chapter in chapterlist)
                {
                    dic.Add(chapter.Id, chapter);
                }
                foreach (var chapter in dic.Values)
                {
                    if (dic.ContainsKey(chapter.Pid))
                    {
                        if (dic[chapter.Pid].Children == null)
                            dic[chapter.Pid].Children = new List<ResChapter>();
                        dic[chapter.Pid].Children.Add(chapter);
                    }
                }
                var dateTree = dic.Values.Where(t => string.IsNullOrEmpty(t.Pid)).ToList();
                return dateTree;          
        }
        #endregion

获取上属父级部门：

try{

string sql = string.Format(@"SELECT a.[Name] [EmployeeName],a.Mobile [EmployeePhone],b.Name [DepartName],b.Id [DepartId],b.PDepartmentId [ParentId]
FROM [HYSYZSCCODB].[dbo].[Employee] a
inner join [HYSYZSCCODB].[dbo].[Department] b on b.EmployeeId = a.Id
where  b.IsValid='true' and a.Mobile =" + "'" + Office.手机.Trim() + "'");
                        var entity = container.Database.SqlQuery<OfficeDTO>(sql).FirstOrDefault();//当前事务所主任的部门
                        if (entity.ParentId.HasValue)
                        {
                            var data = GetParentDeparts(entity.ParentId.Value, list);//获取上级所有部门
                            data.Add(entity);                 //再把自身加上
                            ids = data.Select(f => f.DepartId).ToList();
                        }
                        ids.Add(entity.DepartId);  
}
catch(Exception ex){

} 
}



  #region 递归获取父级部门
        public List<OfficeDTO> GetParentDeparts(Guid parentId, List<OfficeDTO> list)
        {
            using (var container = new TRA_EXTContainer())
            {

                //根据父节点获取选项集合
                string sql = string.Format(@"SELECT a.Name [DepartName],a.Id [DepartId],a.PDepartmentId [ParentId]
FROM [HYSYZSCCODB].[dbo].[Department] a
where  a.IsValid='true' and a.Id = " + "'" + parentId + "'");
                //这里改成你的数据库表
                var entity = container.Database.SqlQuery<OfficeDTO>(sql).FirstOrDefault();
                if (entity != null)
                {
                    list.Add(entity);
                    if (entity.ParentId.HasValue)
                    {
                        GetParentDeparts(entity.ParentId.Value, list);
                    }
                }
            }
            return list;

        }
        #endregion

原文链接：https://www.cnblogs.com/likui-bookHouse/p/9579944.html