將一個有層級關級的數據表按父子關係進行排序整理并返回

我們在很多時候，都要顯示TreeView或TreeGrid. 像jqGrid這種控件可以顯示TreeGrid.
但是jqGrid要想顯示正確，必須在傳遞給它數據之前，要將數據集按父子關係排序好。即：

ID|ParenetID|value
-------------------
1 |0        |....
2 |1        |....
3 |2        |....
4 |1        |....

private void button1_Click(object sender, EventArgs e)
        {
            DataSet ds = new DataSet();

            DataTable dt = new DataTable();

            dt.Columns.AddRange(new DataColumn[] 
            {
                new DataColumn("SysID"),
                new DataColumn("ParentSysID") ,
                new DataColumn("SomeValue") ,
                new DataColumn ("depth"),
                new DataColumn ("seqNo",typeof(int))
            }) ;

            DataRow dr = dt.NewRow();
            dr[0] = "1";
            dr[1] = "0";
            dr[2] = "value";
            dr[3] = "0";
            dr[4] = 1;
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr[0] = "2";
            dr[1] = "1";
            dr[2] = "value";
            dr[3] = "1";
            dr[4] = 3;
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr[0] = "3";
            dr[1] = "1";
            dr[2] = "value";
            dr[3] = "1";
            dr[4] = 2;
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr[0] = "4";
            dr[1] = "2";
            dr[2] = "value";
            dr[3] = "2";
            dr[4] = 1;
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr[0] = "5";
            dr[1] = "0";
            dr[2] = "value";
            dr[3] = "0";
            dr[4] = 10;
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr[0] = "6";
            dr[1] = "0";
            dr[2] = "value";
            dr[3] = "0";
            dr[4] = 5;
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr[0] = "7";
            dr[1] = "5";
            dr[2] = "value";
            dr[3] = "1";
            dr[4] = 1;
            dt.Rows.Add(dr);

            DataTable dt1 = dt.Clone();
            var d = dt.AsEnumerable().Min(m => m.Field<string>("depth"));
            var a = dt.AsEnumerable().Select(m => { return new {sysid = m.Field<string>("sysID"),seqno = m.Field<int>("seqNo"), depth = m.Field<string>("depth") }; }).OrderBy(k => k.depth);
            var c = a.First().depth;
            var k1 = a.First().sysid;

            RecrusionLook<string,string>(dt, dt1, d, default(string));

        }

        private void RecrusionLook<T,K>(DataTable source, DataTable target, T depth, K parentSysID)
        {
            var result = from r in source.AsEnumerable()
                         where (r.Field<T>("depth").Equals(depth) || depth == null || depth.Equals(default(T))) && (r.Field<K>("ParentSysID").Equals(parentSysID) || parentSysID == null  || parentSysID.Equals(default(K)))
                         orderby r.Field<int>("seqNo")
                         select r;

            //result.Select(i => { target.ImportRow(i); RecrusionLook(source, target, "", i.Field<string>("sysID")); return; });
            foreach (var row in result)
            {
                target.ImportRow(row);
                RecrusionLook<T, K>(source, target, default(T), row.Field<K>("sysID"));
            }

        }