Update Panel ,Default Button and FireFox

ASP.Net 2.0 comes up with a new concept called "Default Button" which is one button on the form will work as default button. Whenever we press the enter button default button will be called.

As for example: In a text box after typing you press enter your default button's event will be fired.

However, the one thing that was bothering me with the Default Button is it worked like a charm in IE. In Firefox, it behaved like the weirdly. The problem wasn't that it didn't do a postback. That it did. What it didn't do was hit the server side event (the button click event).
When you are selected in any textbox and you press enter, IE will submit this and hit the button click even. However with FireFox, it will only submit - not call the onclick event.

To solve this add: UseSubmitBehavior="False" to your submit button. Now you can press enter whenever you want in your form and it will do the proper submit regardless of IE or Firefox.

Enjoy..
Happy Programming…

ASP.NET Page Life Cycle

1. Object Initialization

A page’s controls (and the page itself) are first initialized in their raw form. By declaring your objects within the constructor of your C# code-behind file (see Figure 1), the page knows what types of objects and how many to create. Once you have declared your objects within your constructor, you may then access them from any sub class, method, event, or property. However, if any of your objects are controls specified within your ASPX file, at this point the controls have no attributes or properties. It is dangerous to access them through code, as there is no guarantee of what order the control instances will be created (if they are created at all). The initialization event can be overridden using the OnInit method.

2. Load Viewstate Data

After the Init event, controls can be referenced using their IDs only (no DOM is established yet for relative references). At LoadViewState event, the initialized controls receive their first properties: viewstate information that was persisted back to the server on the last submission. The page viewstate is managed by ASP.NET and is used to persist information over a page roundtrip to the server. Viewstate information is saved as a string of name/value pairs and contains information such as control text or value. The viewstate is held in the value property of a hidden control that is passed from page request to page request. As you can see, this is a giant leap forward from the old ASP 3.0 techniques of maintaining state. This event can be overridden using the LoadViewState method and is commonly used to customize the data received by the control at the time it is populated. Figure 2 shows an example of overriding and setting viewstate at the LoadViewState event.

3. LoadPostData Processes Postback Data

During this phase of the page creation, form data that was posted to the server (termed postback data in ASP.NET) is processed against each control that requires it. When a page submits a form, the framework will implement the IPostBackDataHandler interface on each control that submitted data. The page then fires the LoadPostData event and parses through the page to find each control that implements this interface and updates the control state with the correct postback data. ASP.NET updates the correct control by matching the control’s unique ID with the name/value pair in the NameValueCollection. This is one reason that ASP.NET requires unique IDs for each control on any given page. Extra steps are taken by the framework to ensure each ID is unique in situations, such as several custom user controls existing on a single page. After the LoadPostData event triggers, the RaisePostDataChanged event is free to execute.

4. Object Load

Objects take true form during the Load event. All object are first arranged in the page DOM (called the Control Tree in ASP.NET) and can be referenced easily through code or relative position (crawling the DOM). Objects are then free to retrieve the client-side properties set in the HTML, such as width, value, or visibility. During Load, coded logic, such as arithmetic, setting control properties programmatically, and using the StringBuilder to assemble a string for output, is also executed. This stage is where the majority of work happens.

5. Raise PostBack Change Events

As stated earlier, this occurs after all controls that implement the IPostBackDataHandler interface have been updated with the correct postback data. During this operation, each control is flagged with a Boolean on whether its data was actually changed or remains the same since the previous submit. ASP.NET then sweeps through the page looking for flags indicating that any object’s data has been updated and fires RaisePostDataChanged. The RaisePostDataChanged event does not fire until all controls are updated and after the Load event has occurred. This ensures data in another control is not manually altered during the RaisePostDataChanged event before it is updated with postback data.

6. Process Client-Side PostBack Event

After the server-side events fire on data that was changed due to postback updates, the object which caused the postback is handled at the RaisePostBackEvent event. The offending object is usually a control that posted the page back to the server due to a state change (with autopostback enabled) or a form submit button that was clicked. There is often code that will execute in this event, as this is an ideal location to handle event-driven logic. The RaisePostBackEvent event fires last in the series of postback events due to the accuracy of the data that is rendered to the browser.
Controls that are changed during postback should not be updated after the executing function is called due to the consistency factor. That is, data that is changed by an anticipated event should always be reflected in the resulting page.

7. Prerender the Objects

The point at which the objects are prerendered is the last time changes to the objects can be saved or persisted to viewstate. This makes the PreRender step a good place to make final modifications, such as changing properties of controls or changing Control Tree structure, without having to worry about ASP.NET making changes to objects based off of database calls or viewstate updates. After the PreRender phase those changes to objects are locked in and can no longer be saved to the page viewstate. The PreRender step can be overridden using OnPreRender .

8. ViewState Saved

The viewstate is saved after all changes to the page objects have occurred. Object state data is persisted in the hidden object and this is also where object state data is prepared to be rendered to HTML. At the SaveViewState event, values can be saved to the ViewState object, but changes to page controls are not.

9. Render To HTML

The Render event commences the building of the page by assembling the HTML for output to the browser. During the Render event, the page calls on the objects to render themselves into HTML. The page then collects the HTML for delivery. When the Render event is overridden, the developer can write custom HTML to the browser that nullifies all the HTML the page has created thus far. The Render method takes an HtmlTextWriter object as a parameter and uses that to output HTML to be streamed to the browser. Changes can still be made at this point, but they are reflected to the client only.

10. Disposal

After the page’s HTML is rendered, the objects are disposed of. During the Dispose event, you should destroy any objects or references you have created in building the page. At this point, all processing has occurred and it is safe to dispose of any remaining objects, including the Page object. You can override Dispose.

Reference : -http://www.techinterviews.com/?p=176

Alternate text for images for different browsers

To show any picture or image on the webpage either img tag is used or <asp:Image> tag is used. We also put some alternate text for the image. Alternate text can be used to show some details on the screen related to the image. Alternate text is displayed when mouse is over the image. Internet explorer shows a cross sign which means that image is not available on the server where FireFox shows the alternate text on the screen instead of cross sign.

To show alternate text on the image we use
"alt" attribute for img tag .
"Alternatetext" attribute for asp:Image.

But the funny side of these attributes is they are not supported by Firefox. If you use any of these attribute to show alternate text then alternate text is not displayed in Firefox.

After some hard work I found a common solution which is supported by most browsers. Solution is to use " title" attribute instead of "alt" attribute. This attribute is supported by all the browsers.
<img src="sunset.jpg" title="Image1"> </img>

So if you are making an application for different browser stop using alt attribute and switch to title attribute.

Enjoy.