LINQ lambda syntax for counting number of sequence

Question

User-34860367 posted

Hello all,

I got table Student records in database as follows:

ExamDate          Test            Result
01/21/2016         Math           Pass
06/02/2016         Art               Pass
05/31/2017         Math           Fail
06/28/2017         Art              Pass
07/03/2017         Math          Pass
07/19/2017         Art              Fail
08/01/2017         Math          Fail
09/13/2017         Art              Fail
09/15/2017         Math          Fail
10/01/2017         Art              Fail
10/10/2017         Math          Pass
10/11/2017         Art             Fail

....

In above sample data, there are 3 consecutive fails (yellow highlight) for Art test and 1 consecutive fail (blue highlight) for Math test. Anyone can help me to write LINQ lambda to counting how many sequential consecutive fails each test (Math, Art) based on sorting exam date?

Thanks in advance.

Answer 1

User1520731567 posted

Hi avt2k7，

In above sample data, there are 4 sequential fails in a row. Anyone can help me to write LINQ lambda to counting how many sequential fails in a row based on exam date?

Do you mean you want to get the number of consecutive failure records?

Single failure record is not counted？

In your code,it should be 5?

If so, I think could nest loops by foreach,it is easier to implement than linq,I make a demo,you could refer to it:

 List<sequential> model = new List<sequential>();
            model.Add(new sequential { ExamDate = Convert.ToDateTime("2018-01-01"), Test = "aa", Result = "pass" });
            model.Add(new sequential { ExamDate = Convert.ToDateTime("2018-01-01"), Test = "bb", Result = "fail" });
            model.Add(new sequential { ExamDate = Convert.ToDateTime("2018-01-01"), Test = "cc", Result = "pass" });
            model.Add(new sequential { ExamDate = Convert.ToDateTime("2018-01-01"), Test = "aa", Result = "fail" });
            model.Add(new sequential { ExamDate = Convert.ToDateTime("2018-01-01"), Test = "bb", Result = "fail" });
            model.Add(new sequential { ExamDate = Convert.ToDateTime("2018-01-01"), Test = "cc", Result = "fail" });//the count should be 3
            model.Add(new sequential { ExamDate = Convert.ToDateTime("2018-01-01"), Test = "aa", Result = "pass" });

            var count = 0;//get number of sequence
            var jcount = 1;

            for (var i = 0; i < model.Count; i++)
            {
                for (var j = jcount; j < model.Count; j++)
                {
                    if (model[i].Result == model[j].Result)
                    {
                        count++;
                        break;
                    }
                    else
                    {
                        jcount++;
                        break;
                      
                    }
                }

            }

Finally,check the value of variable count,look the picture:

Best Regards.

Yuki Tao

Answer 2

User-34860367 posted

Hello,

Thanks. In my problem,  I want to count the number of consecutive failure records for each test. That mean a single failure record is not counted. Please see the above modifications on my problem. I am looking for LINQ to solve my issue but not sure any solution for it?

Answer 3

User1520731567 posted

Hi avt2k7,

ExamDate          Test            Result
01/21/2016         Math           Pass
06/02/2016         Art               Pass
05/31/2017         Math           Fail
06/28/2017         Art              Pass
07/03/2017         Math          Pass
07/19/2017         Art              Fail
08/01/2017         Math          Fail
09/13/2017         Art              Fail
09/15/2017         Math          Fail
10/01/2017         Art              Fail
10/10/2017         Math          Pass
10/11/2017         Art             Fail

Unclear,why 10/11/2017         Art             Fail is also in sequence.

There is a pass in front of it.

Best Regards.

Yuki Tao

Answer 4

User-34860367 posted

Hello,

There are two different tests: Math and Art. There is a Pass for Math record before your indicated Art record but we cannot count for not consecutive fail because it is not the same test. 

Let me clear. Per highlights that showed two consecutive failures that count one sequential fail. Therefore, 4 yellow highlights should be counted 3 sequential fails and 2 blue highlights for 1 sequential fail. 

Anyway, I found the solution for it from another forum.