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

Migrating an ASP.NET MVC 4 app from Azure websites to WinHost

By
About a week ago I've to migrate an ASP.NET MVC 4/EF5 application from Azure websites to WinHost. While the process was really smooth, there were some caveats related to database connections that I want to share with you. Create and setup the ftp profile on VS and configure the connection string was really easy, WinHost provide you those values and there is nothing special here. But once you deploy your website and try to see it online, you may get the “yellow screen of dead” with the message: "A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)" Assuming you wrote the connection string properly, this happens because you cannot use the default connection name in your web.c
2 comments
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

How to replace text with images on Word documents using C#

By
This post it’s a reply to a question I got from a previous post that shows how to work with Word templates from C# code . If you haven’t read it, I recommend to do so because I’m not going into details here. But basically it was about how to create a Word document from a template and perform same text manipulation. So, the question from Marcel Kieboom  was “Do you know if it would be also possible to replace one of the words with an image which is locally stored?” The answer is yes, and this is how you can do that. Based on the same convention I had used in the previous post, I should have a template like this: What I’m trying to do here is replace the text [angus-young] for an actual pic of Angus. The technique I’m using it’s pretty common on web sites and basically consist in have an image with a matching name for each keyword I want to replace and then create the image path dynamically. This is the C# code to do that. * When I execute the f
19 comments
Read more