One of the main goals behind relational databases design is reduce/eliminate the amount of duplicated data. In order to do that, they split the data into multiple tables and relate them by FK. While this works really well in database terms, they don’t when it comes to searching or loading data (In highly normalized database we usually need a lot of JOINs)Continuing with an example that we were working on previous posts (products by category) we can see this design lines in action.
The goal of our report is allow the users to select a category, and based on that category, fetch the corresponding list of products. The problem is, if we look at the products table, the product's category is and ID (numeric), which is hard to remember and does not make any sense on his own. In this kind of scenarios, we can use the autocomplete control. This control will allows to the user to filter by description (category name) or any field that make sense to him/her and pass to the report engine the corresponding ID to filter the relational data (in this case, the category ID).To get an autocomplete in our dialog, we need to define a class that looks something like this:
* Annotations are required because we are working with a "legacy database” wich does not follow the NRapid conventions, more on this in future posts.
As you may already guess, CategoryName is the field that we are going to use to provide some sort of searching feature, and CategoryID is the field we will use to query the database.
Ones this class is done, we only need to add a property to the nested class “Dialog” (seen in previous posts) and NRapid will take cares of the rest.
When executing the report, you will see a textbox labeled “category”, pressing F2 will a show a list of categories, select one and confirm the dialog.
On the next post, customizing autocompletes. Stay tuned!
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