Question

I have table that has multiple data for the same Id. I need to combinations on this data.

For example this the table contain

ID    Visit DAte       Visit number    Rational 
-----------------------------------------------
1     14/05/2011           1           new
1     15/06/2012           2           Emergency 
1     17/07/2012           3           Check-Up

up to 20 visit

The result that I want is like this

ID    Visit DAte       Visit number    Rational 
-------------------------------------------------
1     14/05/2011           1           new
1     15/06/2012           2           Emergency 
1     17/07/2012           3           Check-Up

1     14/05/2011           1           new
1     15/06/2012           2           Emergency 
1     19/07/2012           4           follwo-up

1     14/05/2011           1           new
1     15/06/2012           2           Emergency 
1     18/12/2012           5           Check-Up

etc.... 

The last one will be

1     14/01/2011           18          Referral 
1     15/02/2012           19          Check-up
1     18/10/2012           20          Emergency

Can I do this by query?

//– I define a class and I define a list from that class

public struct ACVsize5
{
    public int ID;
    public DateTime date;
    public int RaId;
    public int HpId;
    public int DgId;
    public int VisitNum;
}

List<ACVsize5> patient = new List<ACVsize5>();

I used this quer but this select two value but i need to get 3 or more

var query = patient.SelectMany((value, index) => patient.Skip(index + 1),
                          (first,second) => new { first, second });

//– edit

I have to check the combination for one patient to match it with other 4 patients

I came up with generate the first combination if it is match i continue to generate the rest but this operation took long time process how i can increase the performance for the code below ?

for (int j = 0; j < 10000; j++)
        {

            int id1 = getid(names[j].ToString(), 10000);

            for (int t = 0; t < 10000; t++)
            {
                generate_firstACV5A(id1, nvisit(id1), names[j].ToString());

                int id2 = getid(names[t].ToString(), 10000);
                if (id1 == id2) { }
                else
                {
                    generate_firstACV5B(id2, nvisit(id2), names[t].ToString());

if (comparefirst()==true)
                    {

if (count == 0)
                        {
                            safecount++;
                            if (safecount == 4) break;
                        }

Answer 1

Here’s some example code that will generate sets of 3. I don’t know how an ORM will handle this if you let it handle the querying but if you have it locally as objects.

var queried = ... // example:  Enumerable.Range(1, 20).Select(n => new { FK = n });

var sets =
    from a in queried
    from b in queried
    from c in queried
    where a.FK < b.FK && b.FK < c.FK
    select new { a, b, c };

Using your code:

List<ACVsize5> patient = ... // filled by you but I assume a single unique ID

var sets =
    from a in patient
    from b in patient
    from c in patient
    where a.VisitNum < b.VisitNum && b.VisitNum < c.VisitNum
    select new {a, b, c}