Solved

LINQ GroupBy

Posted on 2014-03-03
7
231 Views
Last Modified: 2016-02-10
Hi Experts,

I need your help to add grouping by T.tid   in this code. Thank you in advance.


                    var mydata = db.data
                   
                    .Where(T => T.some.Any(F => F.my_id == another_id))
                   
                    .ToArray()
                 
                    .Select(T => new MyInfo
                    {
                        TId = T.tid,
                        PData = T.data
                       
                     
                    }).ToArray();
0
Comment
Question by:fpoyavo
  • 4
  • 3
7 Comments
 
LVL 62

Expert Comment

by:Fernando Soto
ID: 39902348
Hi fpoyavo;

What is the data type of T.tid? Because if you create a grouping it will return a hierarchical data object. What is also the data type of MyInfo.Tid? Because it will need to store that object.

Can you show in a diagram what you want that grouping to look like or what you need it to look like.
0
 
LVL 1

Author Comment

by:fpoyavo
ID: 39903027
T.tid is int. MyInfo.Tid is int. MyInfo.PData is string.
0
 
LVL 62

Expert Comment

by:Fernando Soto
ID: 39903069
So what are you trying to accomplish by grouping in the query?
0
3 Use Cases for Connected Systems

Our Dev teams are like yours. They’re continually cranking out code for new features/bugs fixes, testing, deploying, testing some more, responding to production monitoring events and more. It’s complex. So, we thought you’d like to see what’s working for us.

 
LVL 1

Author Comment

by:fpoyavo
ID: 39905456
To eliminate duplicated data
0
 
LVL 62

Expert Comment

by:Fernando Soto
ID: 39905468
Grouping will not get rid of duplicates. When you say duplicates does that mean that all columns having the same values or certain columns only.
0
 
LVL 1

Author Comment

by:fpoyavo
ID: 39905554
Some of them. Not all.
0
 
LVL 62

Accepted Solution

by:
Fernando Soto earned 500 total points
ID: 39907759
Hi fpoyavo;

The IEqualityComparer below is used to see if two rows in the database table can be considered duplicates. The IEqualityComparer is only considering two columns to test whether they are considered duplicates or not. If more columns are needed to determine  if they are duplicate then you must add those columns as well.

// See comment below
var ec = new OrderEqualityComparer();

// In the query you need to add the Distinct method after the first ToArray.
var mydata = db.data
               .Where(T => T.some.Any(F => F.my_id == another_id))
               .ToArray()
               .Distinct(ec)
               .Select(T => new MyInfo
               {
                   TId = T.tid,
                   PData = T.data              
               }).ToArray();

// This class is used to match two data object from the database table
// data to see if they are considered duplicates.               
class OrderEqualityComparer : IEqualityComparer<data>
{

    public bool Equals(data d1, data d2)
    {
        if (d1.TID == d2.TID & d1.OtherCoulmn == d2.OtherCoulmn)
        {
            return true;
        }
        else
        {
            return false;
        }
    }


    public int GetHashCode(data d)
    {
        int hCode = d.TID.GetHashCode() ^ d.OtherCoulmn.GetHashCode();
        return hCode.GetHashCode();
    }

}

Open in new window

0

Featured Post

DevOps Toolchain Recommendations

Read this Gartner Research Note and discover how your IT organization can automate and optimize DevOps processes using a toolchain architecture.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

This article describes relatively difficult and non-obvious issues that are likely to arise when creating COM class in Visual Studio and deploying it by professional MSI-authoring tools. It is assumed that the reader is already familiar with the cla…
This document covers how to connect to SQL Server and browse its contents.  It is meant for those new to Visual Studio and/or working with Microsoft SQL Server.  It is not a guide to building SQL Server database connections in your code.  This is mo…
This Micro Tutorial will teach you how to censor certain areas of your screen. The example in this video will show a little boy's face being blurred. This will be demonstrated using Adobe Premiere Pro CS6.
Migrating to Microsoft Office 365 is becoming increasingly popular for organizations both large and small. If you have made the leap to Microsoft’s cloud platform, you know that you will need to create a corporate email signature for your Office 365…

867 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

18 Experts available now in Live!

Get 1:1 Help Now