So far in this series of posts I created a search page that uses AJAX to fetch the results and display them using a modified version of the WebFX ColumnList control.
The only thing left to do to meet the requirements is add support for paging and sorting.

We already have the paging and sorting parameters in the SearchParameters object, so we're sending these parameteres and returning onlt the first page of the results.
Now we need to add paging buttons and enable users to view the other pages.
We also want to cache pages and support prefetching of the next page.


The Pager Control
I wanted to make a reusable paging control that I can use whenever I need paging support.

The main method of the pager control is ShowPage, this method is called with the page index and if the page is not in the cache it will call the server side method to get that page.
Before calling the ShowPage method we need to set some parameters to let the pager know what we want to do.
-ServerSideMethod - the name of the method to call
-ServerMethodType - 1 for a web service method, 2 for PageMethods
-UsePredictiveFetching - when true, the next page will be fetched and cached
-ShowPageCallback - a reference to a method for showing the page (needed because fetching a page is done asynchronously and the pager can be used by different classes)
-SearchParameters - a SearchParameters object that will be sent to the server side method, the pager control will set the paging and sorting parameters every time the ShowPage method is called, but the search specific parameters won't change between pages.

The Pager JavaScript Class:

Pager.js.txt


In the updated Search function the Pager class is created the first time the function is called, the SearchParameters are set and the ShowFirstPage method is called (this method simply calls ShowPage with the value 1).
The pager variable is declared outside of the function because we need it later for showing other pages (and if we created it every time, there will be no point for the page caching).

The updated Search function:

I renamed the onComplete method to reflect that it is now used to show the grid and not as the onComplete call back to the server side call.
You can also see that I moved the searchResultsObject declaration outside of the function. The reason for doing that is to keep the same positions and widths for columns (If the ColumnList is created everytime a page is shown any changes the user made to the widths and positions of columns will be reset).


The Pager class has two methods that can be used for next/previous paging, the ShowNextPage and ShowPreviousPage. It also has two methods for showing the first and last pages.
Adding buttons to control the paging is easy, you can also use the TotalPages value to create direct page links.


Sorting when there's more than one results page.
If there's only one results page the WebFX control can be sorted on the client side, but when there's more than one page we need to change the sorting paramters in SearchParameters and execute the search again.
If you take a look at the Pager class, you can see the Sort method and all it does is change the sorting parameters, clear the page cache and call the ShowFirstPage method.

The Sort method should be called from the grid, when a column header is clicked. Since the WebFX control already support sorting, all I had to do is add a call from the WebFXColumnList.sort function to the Pager's Sort method.
I also wanted to cancel the client side sorting if there's more than one page, no reason to sort on the client side and then replace the whole grid with the new sorted data from the server side.
I added a property to the ColumnList called SortingCallback, and in the showGrid function I set the value of this property to the pager's sort method.



Let's see what we have so far
1. A search page with support for paging, pre-fetcing the next page and caching previous pages.
2. A grid that supports column dragging, resizing, and formatting and links in the cell contents.
3. Easy maintainance. Adding a new search parameter requries only a simple update to the HTML form and the stored procedure, no need to touch the server side code at all.
4. Better performance. Because we only transfer the page data instead of refreshing the entire page (or loading the whole grid's HTML with an update panel), the size of the download is much smaller. Also, caching saves more requests for the same data and pre-fetching gives the user a better experience by having the next page ready faster.

and, best of all, with this implementation I just saved myself a lot of work. From now on, the DBA and designer can create search pages without me being involved. I actually made it even easier by moving the search function inside another class, and the only code that needs to be written is a call to a function with the values for some properties.


What's next? Some advanced features...
This framework will allow you to create pages easily without having to recompile you code but there are some other features that can be added to make it even cooler.

Saved Searches
Allowing users to saves their favorite and most used searches is a great feature that will be easy to implement.
By using the FormController's CollectFormValues to get a JSON of the search parameters and saving these parameters with some name, it should be easy to load the values back to the form later.
Most of the work will be the function that sets the values for the form elements. Apart from that we need to add some HTML for saving and loading searches, a text box with a button for saving and a drop down with a button for loading. Should'nt be too hard.

New search results alerts
Once we have the JSON saved on the server side we can execute this searches at any time, we just need to deserialize the JSON back to the SearchParameters object and execute a search.
It should be very easy to create a service that executes searches periodically and sends a notification when new results are found.

Grid Personalization
Different users might use the same search pages for different things and it might be easier for each user to get the results grid he way they want it. Since we already have a grid that supports setting the widths and positions of columns, we can save this properties for each user and load them back.
In my implementation of this feature I simply saved the column ids, positions and widths for each user and after the default grid is created I just ran over the columns and re-set this properties.

Dynamically created forms
By adding support for dynamically created forms, I can move the whole process of adding a new search page to the database layer. Add a stored procedure, add the data query, columns and form input controls in the database, and open a generic search page with the name of the form to load. Now you don't even need to upload an HTML file.
Of course, getting to a place where these forms look good enough and support all the layout requirements might be too hard to make it worth it.


Files:
 
AjaxSearchSamplePart5.zip (935.70 kb)
This zip file contains all the code shown in this series and some additional code that was mentioned.