Upgrading ASMX web services to WCF

by Ishai Hachlili 15. June 2008 09:21

There is a lot of information on the web on using WCF for JSON, but I figured I’ll writing something short on the way I use it.

When I decided to try WCF, the first thing I noticed was how simple it was to upgrade. All you need to do is add a new WCF Service to the web project, copy the code from the ASMX service, change the [ScriptService] to [ServiceCntract] and the [WebMethod] tags to [OperationContract] and add some definitions in the web.config file.
You’re supposed to use a separate Interface to define the service contract, but it’s not a must and you can add the tags to the actual class with the implementation.

The second thing I noticed is that I can get JSON by changing some configuration settings.
When I was working on the AJAX search page, WCF was not around (it was by the time I posted the series on it here). I used XSLT to transform data to JSON and arrays. It was another step I had to do on the server side but it’s worth it, JSON is smaller than XML and very easy to work with in JavaScript.
With WCF I just change a small definition and I get the results in JSON, no need for the XSLT transformation.

Another thing we get with WCF is Data Contracts. The way I’m using it in this sample, it’s pretty much the same as using the .Net AJAX GenerateScriptType.
All I had to do is add a [DataContract] tag to the class and [DataMember] tags to each property.
I think it’s better to define this on the exposed class itself instead of adding some register definition in a web service.

The attached project is the same search page sample with the WCF service. The changes to look for are:

  • The new DataService.svc file
  • The Entities.QueryParameters classes now have the DataContract tags
  • web.config has the new serviceModel section at the end, that defines the service as an HTTP JSON enabled service
  • default.aspx – the service defined in the ScriptManager was changed to the svc file and the path was updated in the javascript Search method

 

WcfAjaxSearchSample.rar (883.99 kb)

Tags: , ,

AJAX | Asp.Net | WCF

My take on implementing searches with AJAX (Part 5)

by Ishai Hachlili 15. February 2008 16:39

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 (4.93 kb)

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:

var pager = null;

function Search() {
var fc = new FormController();
var searchParams = fc.CollectFormValues("searchFormContainer");
searchParams.PageSize=20;
searchParams.SortColumn="FirstName";
searchParams.SortOrder="ASC";
searchParams.QueryName="SearchClients";
searchParams.ColumnCollectionName="ClientsSearchResults";

if (pager==null) {
pager = new Pager();
pager.ServerMethodName = 'IshaiHachlili.MyTakeOnDotNet.WebServices.ContentsWS.DoSearch';
pager.ServerMethodType = 1;
pager.ShowPageCallBack = showGrid;
pager.UsePredictiveFetching = true;
}

pager.SearchParams = searchParams;

pager.ClearCachedPages();
pager.ShowFirstPage();
}

var searchResultsObject;
function showGrid(result) {
eval(result);

if (typeof(aColumns)!="undefined") {
if (TotalPages>0) {
pager.TotalPages=TotalPages;
}

var el =$get("searchResultsContainer"); //the element that will contain the grid
if (searchResultsObject == null) {
var searchResultsObject = new WebFXColumnList();
searchResultsObject.SortingCallback = pager.Sort.bind(pager);
searchResultsObject.create(el, aColumns);
} else {
searchResultsObject.clear();
}

searchResultsObject.addRows(aData);
} else {
alert('No results returned');
}
}


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 (935.24 kb)

This zip file contains all the code shown in this series and some additional code that was mentioned.

 

Tags: ,

AJAX | Javascript

My take on implementing searches with AJAX (Part 4)

by Ishai Hachlili 12. February 2008 13:40

In the previous posts in this series I collected the form values, executed the search and processed the search results columns on the server side.

Now it’s time to return the results to the client side and display the search results grid.

I’m going to use the WebFX columnlist for my grid. This is my favorite javascript grid control.
It allows column resizing and drag & drop reordering as well as client side sorting (which will be great for one page search results).
It doesn’t support any formatting or links in the grid, so I’ll have to make some upgrades to it.

If you look at the documentation for the WebFXColumnList, you can see it uses an array of the column names and an array of data rows where each row is an array of values (that should be in the same order as the column names).

JavaScript sample – showing a grid using WebFXColumnList

var aColumns = [
'Rank',
'Flavor',
'Color',
'Share'
];

var aData = [
['1','Vanilla','White','29%'],
['2','Chocolate','Brown','8.9%'],
['3','Butter pecan','Light brown','5.3%'],
['4','Strawberry','Pink','5.3%'],
['5','Neapolitan','Greenish brown','4.2%'],
['6','Chocolate chip','Brown','3.9%'],
['7','French vanilla','Yellowish white','3.8%'],
['8','Cookies and cream','Light brown','3.6%'],
['9','Vanilla fudge ripple','White', '2.6%'],
['10','Praline pecan','Brown','1.7%'],
['11','Cherry','Red','1.6%'],
['12','Chocolate almond','Brown','1.6%'],
['13','Coffee','Dark brown', '1.6%'],
['14','Rocky road','brown', '1.5%'],
['15','Chocolate marshmallow','Light brown','1.3%']
];

var el = document.getElementById('container');

var o = new WebFXColumnList();
o.create(el, aColumns);
o.addRows(aData);

Sample taken from http://webfx.eae.net/dhtml/collist/usage.html


Right now I have a DataSet, so I need to convert it to these arrays and the best way to do it is with xslt.
Because I want more than just column names returned to the client side, I’m going to use the Column Collection DataTable I created in the previous post for the aColumns array.

My XSLT will create the actual javascript vars, in the client side I'll simply evaluate the returned string and I'll have the variables ready to use

ConvertSearchResultsDS.xslt

<?xml version="1.0"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="text"/>
<xsl:template match="/" >

var aColumns = [<xsl:for-each select="*/Columns">
<xsl:sort select="Position" data-type="number" order="ascending"/>
{
<xsl:for-each select="./*">
<xsl:value-of select="name()"/>:'<xsl:value-of select="."/>'<xsl:if test="position() &lt; last()">,</xsl:if>
</xsl:for-each>
}<xsl:if test="position() &lt; last()">,</xsl:if>
</xsl:for-each>
];


var aData = [<xsl:for-each select="//Data">
[<xsl:for-each select="./*[name()=//Columns/Name]">
'<xsl:call-template name="escape-quotes">
<xsl:with-param name="text" select="normalize-space(text())"/>
</xsl:call-template>'<xsl:if test="position() &lt; last()">,</xsl:if>
</xsl:for-each>]<xsl:if test="position() &lt; last()">,</xsl:if>
</xsl:for-each>
];
</xsl:template>


<xsl:variable name="quote-char">
<xsl:text>'</xsl:text>
</xsl:variable>

<xsl:variable name="escaped-quote">
<xsl:text>\'</xsl:text>
</xsl:variable>


<xsl:template name="escape-quotes">
<xsl:param name="text"/>
<xsl:choose>
<xsl:when test="contains($text,$quote-char)">
<xsl:variable name="pre" select="substring-before($text,$quote-char)"/>
<xsl:variable name="post">
<xsl:call-template name="escape-quotes">
<xsl:with-param name="text" select="substring-after($text,concat($pre,$quote-char))"/>
</xsl:call-template>
</xsl:variable>
<xsl:value-of select="concat($pre,$escaped-quote,$post)"/>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="$text"/>
</xsl:otherwise>
</xsl:choose>
</xsl:template>
</xsl:stylesheet>




I'm going to do the transformation in the web service.
I called the method GetResultString and in the web method code from part 1 I already called it.

protected string GetResultString(DataSet ds, int pageSize)
{
string result = TransformXsl(ds, "~/XSLT/ConvertSearchResultsDS.xslt");
int rowCount = (int)ds.Tables["TotalRows"].Rows[0]["TotalRows"];
result += String.Format("var TotalPages = {0};", CalculateTotalPages(rowCount, pageSize));

return result;
}



TransformXsl is a simple function that takes the dataset and xslt and does the transformation using the XslCompiledTransform class.
CalculateTotalPages returns the number of total pages using the total row count and page size


Displaying the grid

The JavaScript Search function that calls the web method defined a function called onComplete for the callback.
This function will receive the results string, create the WebFXColumnList object, initialize it and add the rows.

function onComplete (result) {
eval(result);

if (typeof(aColumns)!="undefined") {
var el =$get("searchResultsContainer"); //the element that will contain the grid
var searchResultsObject = new WebFXColumnList();
searchResultsObject.create(el, aColumns);
searchResultsObject.addRows(aData);
} else {
alert('No results returned');
}
}


After evaluating the returned javascript code I should have the aData and aColumns variables and from that point I can continue with the create and addRows method calls to display the grid.

The string created by the xslt is not exactly what the WebFXColumnList expects, so I'll need to make some changes to the javascript.

The create method of the ColumnList expects a simple array with names, so I need to go through it and change all references to aColumns.
I replaced the aColumns[i] to aColumns[i].Header when creating the head table.

I also need to add support for hidden columns, I want the create method to skip these. I need to add support for the formatting in the addRows function, and make sure everything else works.

I'm not going to go into all of these changes, but an updated script will be included in the download.


Files:

AjaxSearchSamplePart4.zip (919.09 kb)

 

Tags: , ,

AJAX | Asp.Net | Javascript

About Me

Ishai Hachlili is a web and mobile application developer.

Currently working on Play The Hunt and The Next Line


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