Friday, December 28, 2012

WinForms, paging the DataGridView the right way


I know this may sound like old history, but in the enterprise world there is still a lot of WinForms development. Just a couple of days ago, I had to implement a custom DataGridView capable to work over a butt load of data (100K+ records) and keep responses times acceptables.
I thought paging will be a good way to go, and as WinForms is pretty old nowadays, I supposed it will be easy to find a couple examples on the web.
While in fact I found examples, all of them were incompletes and/or they wouldn't perform well in real world apps... So I decided to roll my own component and post it online. Hopefully, someone else will find it useful ;).


The bread and butter of this solution relies on LINQ and deferred execution. As LINQ takes care of all complicated work, it was quite easy to implement.

This component also supports conditional format, sorting and some search capabilities, but in this post I will concentrate on paging only (I'll cover the rest of the features in future posts).

I’m assuming you are familiar with LINQ (or with how partial application works in C#)

The amazing thing on how this paging implementation works, is that you only have to do a little bit of configuration and the component will take care of the rest. This is how to configure the grid.



To avoid performance killings (and to not spoil deferred execution) the row count should be specified separately.

And this is how internally works.
Configuring

Paging

Notice that when we execute the .ToList()  method we only fetch a small set of records according to the grid’s page size (we don’t fetch the whole thing). In this case instead off fetching 50K records, we are fetching only 1K and caching them for later use. If the user asks for the same page twice, the second time, we will give him a cached version of that page (we hit the database only once per page).

If the data source is mutable, when you detect a change you can invalidate the cahce and then start the whole process all over again.

You can get the code from the github repo.

5 comments:

  1. As we still using V10 as our development platform I just discovered that I could not rebuild this as it requires V11 :-)

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    1. You can use VS Express 2012. It is free ;)

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  2. For those who are still working with WinForms like we, draw your attention to a good and enough cheap DataGridView alternative, 10Tec iGrid.NET control (see http://10tec.com/). As for paging, it has a FillWithData method one can use to populate the gird from an ADO.NET datasource. What is important in the context of this blog post, the parameters of the FillWithData method allow the developer to upload the data by portions - which is ideal for paging.

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    1. Anonymous, While I'm OK with people advertising their products, please prefix them with the word _advertise _ ;)

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