Recursive LINQ get hierarchy?

问题

I have this result table after my query

Id    Per_Router       Prod_No  Rout_No
NULL        1           81253   77976
NULL        1           81235   77976
NULL        1           67907   77976
NULL        1           66772   77976 
21202       2           NULL    77976 
41978       1           NULL    77976 
41979       1           NULL    77976

using LINQPAD I want to extract the whole hierarchy. As starting point 77976 but I want to get also for each sub-component ex. 81253, 81235, etc - recursive? Using query from db is very long to get each sub component record (Foxpro 6)

I declare my self a beginner in this

    var query = from p in RoTable 
    where p.Rout_No.Contains("77976")
    select new
    {
        p.Id, 
        p.Per_Router,
        p.Prod_No,
        p.Rout_No,
    };

query.Dump();

Expected results:

Top Level start 77976

      Id    Per_Router       Prod_No  Rout_No
      NULL        1           81253   77976
      NULL        1           81235   77976
      NULL        1           67907   77976
      NULL        1           66772   77976 
      21202       2           NULL    77976 
      41978       1           NULL    77976 
      41979       1           NULL    77976
    Sub-components of 81253
      20373      11           NULL    81253   
      20377      1            NULL    81253   
      20379      1            NULL    81253   
      20388      4            NULL    81253
    Sub-components of 81235
      20265      1            NULL    81235
      28957      1            NULL    81235
      NULL       1            53755   81235
      NULL       1            53788   81235
      NULL       1            59516   81235

    Sub-sub-components 53755
    Sub-sub-components 53788   
    Sub-sub-components 59516      

    Sub-components of 67907
    Sub-components of 66772
    ...
    ...

Can you give me a hint in this? The final code will be integrated into c# project.

回答1:

Try following recursive code. You tables doesn't have a lot of parent/child rows so I didn't get a lot of results. You probably will get better results with actual data

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;

namespace ConsoleApplication65
{
    class Program
    {
        static DataTable dt = null;
        static void Main(string[] args)
        {
            dt = new DataTable();
            dt.Columns.Add("Id", typeof(int));
            dt.Columns.Add("Per_Router" , typeof(int));
            dt.Columns.Add("Prod_No", typeof(int));
            dt.Columns.Add("Rout_No", typeof(int));

            dt.Rows.Add(new object[] {null, 1, 81235, 77976});
            dt.Rows.Add(new object[] {null, 1, 67907, 77976});
            dt.Rows.Add(new object[] {null, 1, 66772, 77976 });
            dt.Rows.Add(new object[] {21202, 2, null, 77976 });
            dt.Rows.Add(new object[] {41978, 1, null, 77976 });
            dt.Rows.Add(new object[] {41979, 1, null, 77976});
            dt.Rows.Add(new object[] {20373, 11, null, 81253   });
            dt.Rows.Add(new object[] {20377, 1, null, 81253   });
            dt.Rows.Add(new object[] {20379, 1, null, 81253   });
            dt.Rows.Add(new object[] {20388, 4, null, 81253});
            dt.Rows.Add(new object[] {20265, 1, null, 81235});
            dt.Rows.Add(new object[] {28957, 1, null, 81235});
            dt.Rows.Add(new object[] {null, 1, 53755, 81235});
            dt.Rows.Add(new object[] {null, 1, 53788, 81235});
            dt.Rows.Add(new object[] {null, 1, 59516, 81235});

            Console.WriteLine("Id    Per_Router       Prod_No  Rout_No");

            ParseTableRecursive(null);

            Console.ReadLine();
        }

        static void ParseTableRecursive(int? parent)
        {
            List<DataRow> group = dt.AsEnumerable().Where(x => x.Field<int?>("Prod_No") == parent).ToList();
            if(group.Count > 0)
            {
                Console.WriteLine();
                Console.WriteLine("Sub-components of {0}", parent == null ? "NULL" : parent.ToString());
                Console.WriteLine();

                foreach (DataRow row in group)
                {
                    Console.WriteLine("{0:5}     {1:5}     {2:5}     {3:5}",
                        row.Field<int?>("Id") == null ? "NULL" : row.Field<int?>("Id").ToString(),
                        row.Field<int?>("Per_Router") == null ? "NULL" : row.Field<int?>("Per_Router").ToString(),
                        row.Field<int?>("Prod_No") == null ? "NULL" : row.Field<int?>("Prod_No").ToString(),
                        row.Field<int?>("Rout_No") == null ? "NULL" : row.Field<int?>("Rout_No").ToString()
                    );

                }

                foreach (int? child in group.Select(x => x.Field<int?>("Rout_No")).Distinct())
                {
                    ParseTableRecursive(child);
                }
            }
        }
    }
}

来源：https://stackoverflow.com/questions/52279476/recursive-linq-get-hierarchy

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