asked on

Linq Query - Multiple Table Selection

Hello. Let's say we have the tables below:

PROJECT
ID Name
1 Roadwork

PROJECTMEMBERS
ID Name
11 John
22 Sally
33 Jane
44 Joan

SIGNOFFS
ID PROJECTID MEMBERID DATEOFSIGNOFF
111 1 11 1/5/2012
222 1 22 1/6/2012
333 2 44 1/9/2012

Each project will have 2 members and each member will sign off on the project. I need a Linq query that will select a project and also the two project members that have signed off on the project (if any).

The required dataset for this example is below:

DATASET:
PROJID PROJNAME MEMBERID1 DATE1SIGNOFF MEMBERID2 DATE2SIGNOFF
1 Roadwork 11 1/5/2012 22 1/6/2012

This dataset will be sent to a dataGrid for display. At this point, I'm not certain how to select multiple rows from the PROJECTMEMBERS table. A full query would be appreciated.

Environment: C#.NET 4.0

adskarcox

ASKER

Note: if there is a better way to do this, than through a single Linq query, I am open to suggestions.

Triskelion

I made a mock-up of the data containers.
The linq generates an ILookup with the project as the key and a key/value pair of the project-member and the signoff objects.
The printing might need a little filtering if the number of members on the project is not as expected.

using System;
using System.Collections.Generic;
using System.Linq;

namespace EE_27633596_CS_CON
{
   public class CProject
   {
      public int intProjectId { get; set; }
      public string strProjectName { get; set; }
      public override string ToString()
      {
         return intProjectId.ToString() + '-' + strProjectName;
      }

      public override bool Equals(object obj)
      {
         return this.ToString().Equals(((CProject)obj).ToString());
      }

      public override int GetHashCode()
      {
         return this.ToString().GetHashCode();
      }
   }

   public class CProjectMember
   {
      public int intMemberId { get; set; }
      public string strMemberName { get; set; }
   }

   public class CSignOff
   {
      public int intSignOffID { get; set; }
      public int intProjectId { get; set; }
      public int intMemberId { get; set; }
      public DateTime dtSignOffDate { get; set; }
   }

   class Program
   {
      static void Main(string[] args)
      {
         List<CProject> lstProjects = new List<CProject>()
         {
            new CProject(){intProjectId=0, strProjectName="Roadwork"},
            new CProject(){intProjectId=1, strProjectName="Crosswalk"},
            new CProject(){intProjectId=2, strProjectName="WaterMain"}
         };

         List<CProjectMember> lstMembers = new List<CProjectMember>()
         {
            new CProjectMember(){intMemberId=100, strMemberName="Tom"},
            new CProjectMember(){intMemberId=101, strMemberName="Dave"},
            new CProjectMember(){intMemberId=102, strMemberName="Joe"}
         };

         List<CSignOff> lstSignOffs = new List<CSignOff>()
         {
            new CSignOff() {intSignOffID=0, intMemberId=100, intProjectId=0, dtSignOffDate=DateTime.Now},
            new CSignOff() {intSignOffID=1, intMemberId=101, intProjectId=0, dtSignOffDate=DateTime.Now},
            new CSignOff() {intSignOffID=2, intMemberId=100, intProjectId=1, dtSignOffDate=DateTime.Now},
            new CSignOff() {intSignOffID=3, intMemberId=102, intProjectId=1, dtSignOffDate=DateTime.Now},
            new CSignOff() {intSignOffID=4, intMemberId=101, intProjectId=2, dtSignOffDate=DateTime.Now},
            new CSignOff() {intSignOffID=5, intMemberId=102, intProjectId=2, dtSignOffDate=DateTime.Now}
         };

         ILookup<CProject, KeyValuePair<CProjectMember, CSignOff>> lkup =
         (
            from so in lstSignOffs
            join p in lstProjects on so.intProjectId equals p.intProjectId
            join m in lstMembers on so.intMemberId equals m.intMemberId
            select new
            {
               k = p,
               v = new KeyValuePair<CProjectMember, CSignOff>(m, so)
            }
         ).ToLookup(k => k.k, v => v.v);

         foreach (var x in lkup)
         {
            Console.WriteLine("{0}: {1}\t{2}\t{3}\t{4}\t{5}\t{6}\t{7}",
               x.Key.intProjectId,
               x.Key.strProjectName,
               x.ElementAt(0).Key.intMemberId,
               x.ElementAt(0).Key.strMemberName,
               x.ElementAt(0).Value.dtSignOffDate.ToShortDateString(),
               x.ElementAt(1).Key.intMemberId,
               x.ElementAt(1).Key.strMemberName,
               x.ElementAt(1).Value.dtSignOffDate.ToShortDateString());
         }
      }
   }
}

Open in new window

adskarcox

ASKER

Why can't this be accomplished with one query? Or even with a few queries working together?

Almost 100 lines of code to accomplish this seems very excessive.

There has got to be a more efficient way.

ASKER CERTIFIED SOLUTION

adskarcox

membership

This solution is only available to members.

To access this solution, you must be a member of Experts Exchange.

Start Free Trial

adskarcox

ASKER

This resolved my issue.