使用Linq生成分类Json数据

public abstract class Category
        {
            public static string GetJson()
            {
                StringBuilder sb = new StringBuilder(500);
                var pr = new ParentCateRepository();
                var cr = new ChildCateRepository();
                var pList = pr.GetAll().Select(a => new { a.ID, a.Name });
                var cList = cr.GetAll().Select(a => new { a.ID, a.Name, a.ParentID });
                foreach (var a in pList)
                {
                    sb.Append("{id:'" + a.ID + "',name:'" + a.Name + "',child:[");
                    var c = cList.Where(i=> i.ParentID == a.ID);
                    foreach (var b in c)
                    {
                        if (b.ParentID == a.ID)
                        {
                            sb.Append("{id:'" + b.ID + "',name:'" + b.Name + "'}");
                        }
                        if (b.ID != c.Last().ID)//注意一定要判断字段，不能判断对象因为两种类型是推测所以不同
                        {
                            sb.Append(",");
                        }
                    }
                    sb.Append("]}");
                    if (a.ID != pList.Last().ID)
                    {
                        sb.Append(",");
                    }
                }
                return "["+sb.ToString()+"]";
            }

生成的数据如下格式:
[{id:'1',name:'计算机',child:[{id:'1',name:'程序设计'}]},
{id:'2',name:'语言培训',child:[{id:'2',name:'英语培训'}]}]