Skip to main content

NRapid, cascade filtering with autocompletes

Image
By

When working with large sets of hierarchical data sometimes you need to provide some sort a cascade filter mechanism. For instance, in a travel agency system, you may want to be able to select a destination, like country or a region, and based on that selection, get some data sets with travel options such as hotel deals, car rentals, and so on….

Continuing with our example (products and categories) I’ll create a dialog with two autocompletes. One will give you whole list of categories and the other a filtered set of products based on the selected category.

Doing this is not so hard but requires a bit of an explanation.
*In this post I’ll be using a nice C#’s feature called partial application. If you don’t know what does this means, don’t worry; just look at it as a magical lambda ;).

When configuring an Autocomplete it’s possible to specify a function to be executed every time the selection changes, this can be done by using the NRapid’s fluent API, and we are going to use this feature to get the selected category and then use that category to filter the list of products.

The code looks something like this:

* If you are not familiar with functional programming this code will look a little odd,....and well..., it is ;)

This code updates the "cat" variable every time the selected category changes and passes it to the method productsByCategory which is wrapped into a function that is partial applied and used as a datasource for the products autocomplete control. This function is invoked internally by the report engine and updates the products list with the proper values. In other words, a whole lot of mess ;)

Execute the report and you will see the two autocomplete controls working together to provide cascade filtering .




As soon as I can, I'll take a look at the NRapid core API and see if it's possible to reduce the ammount of code you need to write in order to get cascade filtering.


You can get the source code of NRapid from here
And the sample app from here
The Northwind database is available from download at http://www.microsoft.com/en-us/download/details.aspx?id=23654


Labels:

Comments

Post a Comment

Popular posts from this blog

Moving to Medium

By
It's been a long time since I want to give medium a try, and finally, I made some time to do it. To get started on the new platform, I'll be doing series on "Getting programming concepts, languages and tools". If it sounds interesting to you, please take a look at the first post  Getting AWK  and spread the word if you like it. I'm not going to migrate old entries to the new web site. They will remain here safe and sound! As usual, thanks for reading!
Post a Comment
Read more

Working with unattended reports

By
In this post I‘ll show you how to create reports that NRapid will execute into an unattended mode. I strongly recommend using this kind of reports in automation scenarios only , and let the user see the print preview dialog in the rest of cases. The only difference between this reports and the standard ones, is that you will cannot make use of dialogs, the runtime will always pass in empty views to the ConfigureReport method. The ConfigureReport method will be executed, but you will have to grab the arguments from somewhere else. The execution pipeline is the same that NRapid uses for standard reports. This is the code to print out the whole list of categories in a dialogless mode. Notice that this report inherits from UnattendedReport class, this class tells to NRapid “run the report unattended”. Also notice that this class comes with a convenience method to configure the report with no arguments. You still can override the one that gets the view data but you will always
Post a Comment
Read more

How to show excel files inside the .NET Webbrowser Control

By
If you are reading this, chances are you been banging your head against the wall for a couple of hours (or even days) trying to show excel files inside the WinForms webbrowser control. Possible reasons you ended up in here: You had working code that got broke after upgrading from Win 7. Your code doesn’t work the same way between machines running different (newer) versions of IE. A download box pops up every time your app tries to show an excel file inside the webbrowser control (you wanna show the actual content). You just have no clue on how to get excel working into the .NET embedded webbrowser control. You are trying to implement IInternetSecurityManager and don’t know where to start. (Or how don’t know how to delegate calls to your security manager). Among many other, maybe….. Yes, COM is a PITA, so is ActiveX and IE (Embedded or full for that matter). And no, showing excel files inside the webbrowser control shouldn’t be that hard, but sometimes we have
3 comments
Read more