Valuable Learnings

This is the simple javascript code to detect whether flash installed on the machine or not! //Look for a version of Internet Explorer that supports ActiveX (i.e., one that's //running on a platform other than Mac or Windows 3.1) or a browser that supports //the plugin property of the navigator object and that has Flash Player 2.0 //installed. //The Check for Internet Explorer is needed as it can play native swf files. var flashSupported; if ( (navigator.appName == "Microsoft Internet Explorer" && navigator.appVersion.indexOf("Mac") == -1 && navigator.appVersion.indexOf("3.1") == -1) || (navigator.plugins && navigator.plugins["Shockwave Flash"]) || navigator.plugins["Shockwave Flash 2.0"]){ flashSupported = true; } else { flashSupported = false; }

In my current project I am working on IPad and there are some specific things need to be applied on IPad. We can detect end user's browser and environment information from the navigator using the following code. var isIPad = navigator.userAgent.match(/iPad/i) != null ;

In one of my current projects, I came across a scenario to play a video based on the users downloading bandwidth. The detection should be done with javascript. There is a technique, to load an image of known size and calculating the bandwidth on basis of time taken to load that image. Though this technique is not 100% reliable, this will give an approximate estimate of bandwidth. Here is the javascript code to find users bandwidth: var userBandwidth = 0; var startTime; var endTime; var imgSize = 39842; var loadTimeInSec; function GetUserBandwidth() { var testImage = new Image(); testImage.src = "bwtest.jpg"; startTime = ( new Date()).getTime(); testImage.onload = CreateDelegate(testImage, DoneWithTest); } function DoneWithTest() { endTime = ( new Date()).getTime(); loadTimeInSec = (endTime - startTime) / 1000; userBandwidth = (imgSize / loadTimeInSec) / 1024; } Here we are loading a...

Before going to the topic, lets know brief about "Delegate": A delegate is like a function pointer, which stores reference of a method. It specifies a method to call and optionally an object to call the method on. They are used, among other things, to implement callbacks and event listeners. We can create and define delegates in Javascript to perform some specific tasks on an object. The following is the code to define delegate. function CreateDelegate(contextObject, delegateMethod) { return function() { return delegateMethod.apply(contextObject, arguments); } } Let us take a simple example and use the delegate in that. Here is the scenario, there is a large image to be loaded on a web page and we need to display the height and width of that image after loading. Delegate method will be very handy in this situation. var image = new Image(); image.src = "test.jpg"; image.onload = CreateDelegate(image, ImageLoaded); function ImageLoaded() { ale...

In all UI Rich web applications, it is very common to pre-load images. General method to do this is to use Javascript. We can load images by creating client side images before page gets loaded. It is a simple technique and can be done with 2 lines of code. var testImage = new Image(); testImage.src = "test.jpg"; With the above lines of code test.jpg will loaded in the DOM. As the images are cached by browsers, whenever we send a new request for test.jpg, the image will be loaded immediately from cache. With this pre-loading technique there wont be any time lag in getting the image also no display lag for the user. This can be used in the scenarios like displaying image gallery with all the thumbnails loaded on first load of the page, image change on hovering/click of some links. We can do this preloading in html page using an image tag with height and width set to zero or wrapping the dynamic image in a hidden div. But, advantage with this approach is the imag wont be loaded ...

Here is another common problem encounters with WCF Service in initial days. Suppose there is a method which returns a List of Objects the proxy will be generated as method which returns an array of objects. Reason: This problem is due to the default interpretation of collections. While generating proxy for the service all the collections are by default interpreted as arrays. That is why all the lists will be converted to arrays. Solution: If you are generating proxy by adding service reference from visual studio directly, there will be a 'advanced' button. Click that button and select the System.Generic.List as your Collection. This will resolve the problem. If you are generating proxy with svcutil here is the command to do the job. svcutil.exe http://ServerName/ServiceName/Servic.svc?wsdl /collectionType:System.Collections.Generic.List`1 or in short svcutil http://ServerName/ServiceName/Servic.svc?wsdl /ct:System.Collections.Generic.List`1 for more information go through this ...

When you are working with WCF service for the first time, generally you will get this error for some reason. Here is the description of the error: WebServiceReference . ServiceClient client = new WebServiceReference . ServiceClient (); WebServiceReference . ImplementationRequest req = new WebServiceReference . ImplementationRequest (); req = client.GetRequest(); Here the Method GetRequest will return an object of ImplementationRequest. Everything will run without any error but the req object will contain all null fields/ majority null fields. Solution: Those nulls are due to error in generating the proxy for the Data Contract defined by the service. Verify that [DataMember] attribute tag is given for all the data fields and [DataContract] for the Class. If those attributes are missing, the object will be generated with null values. If all fields have the tags but the issue is not resolved, then the service reference should be re-added and the proxy should be re-generated. Then t...