Malisa Ncube - .NET Delights

Developing extensible applications (Plugin Frameworks and MEF)

In last few months i have been looking into a number of technologies, methodologies and tricks on how i can design and expedite the development of the EMR software. Some of the critical success factors of this EMR were extensibility because the institution has a huge research component and many research studies have various requirements and new ones come through anytime. Therefore, the EMR architecture is supposed to allow the developer to simply create a plug-in using a VS template and simply add his/her new business objects and compile it and add it to the plug-in folder so it can be loaded by the shell application at runtime.

We also used the Krypton Suite for our user interface. We bought the with source, and we modified the components so that they expose the KryptonRibbonGroup, KryptonRibbon, KryptonRibbonTab and KryptonRibbonRecentDoc. These make it easy for us to create ribbon elements in plug-ins and the shell application will register them at runtime automatically.

While i was doing my research i stumbled on the managed Extensibility Framework (http://www.codeplex.com/MEF) from Microsoft, and think it is really cool. I particularly like that fact that you can use metadata(attributes) to define dependencies in your architecture and those get satisfied at runtime.  There is also more stuff on http://www.codeplex.com/MEFContrib that is interesting about MEF.

In the next couple of weeks i will be frequently blogging about my experiences in working with my custom plug-in framework and my understanding of MEF why i think it has a place in the future of software applications that need to evolve. I will also put my thoughts around what i think would be good as cosmetics or syntactic sugar in MEF and features that i think are vital for my kind of applications.

Cheers!

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Posted On Tuesday, April 21, 2009 9:56 PM | Feedback (1) |

Using lambda or LINQ for pivot tables

In should say that the first time I looked lambda and linq, making pivot tables was not the main thing I thought about. After helping a few people including one at the msdn (http://is.gd/oG8q) social site, I realized that I also needed to use the lambda in my own EMR project.

The problem was to have the lab data of a patient transformed into a pivot table and some of the data summarized by averaging or counting.

I had the data in the table in the following format.

I then had to write a linq expression to produce the following results.

The linq was as follows.

var labResults = from lab in CoreLabResults
                 where lab.Patient == 8
                 group lab by new { lab.Patient, lab.TestNo, lab.CollectedDate }
                     into labtests
                     select new
                     {
                         labtests.Key.Patient,
                         labtests.Key.TestNo,
                         labtests.Key.CollectedDate,
                         MCHC = labtests.Where(lab => lab.TestVar == "MCHC").FirstOrDefault().Result,
                         LYABS = labtests.Where(lab => lab.TestVar == "LYABS").FirstOrDefault().Result,
                         TotalTests = labtests.Count()
                     }

The lambda expression for the above was be as follows

var labResults = CoreLabResults
    .Where(lab => lab.Patient == 8)
    .GroupBy(lab =>
            new
            {
                Patient = lab.Patient,
                AccessionNo = lab.AccessionNo,
                CollectedDate = lab.CollectedDate
            }
            )
    .Select(labtests =>
            new
            {
                Patient = labtests.Key.Patient,
                AccessionNo = labtests.Key.TestNo,
                CollectedDate = labtests.Key.CollectedDate,
                MCHC = labtests.Where(lab => (lab.TestVar == "MCHC")).FirstOrDefault().Result,
                LYABS = labtests.Where(lab => (lab.TestVar == "LYABS")).FirstOrDefault().Result,
                TotalTests = labtests.Count()
            }
);

I still need to find out how I can replace the column names like “MCHC” by computed ones. I may probably need to use the expression trees to dynamically create lambda expressions that have variable number of columns. E.g. in financial statements - I would not want to hardcode column names of each financial period year/quarter.

Apologies – syntax highlighting using Live writer is hell.

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Posted On Tuesday, April 21, 2009 8:55 PM | Feedback (8) |