Life, the Universe and the Internet

I had a recent problem when working with ajax update panels on an asp.net application. I basically had a panel with lots of drop down boxes and text boxes inside it. Whenever a drop down was changed or a value was entered in a textbox, the whole panel would be recalculated as it contained totals and sub totals based on the contents of these boxes.

The problem I had was that I had to include all of the controls inside the update panel otherwise I would have ended up with 20-30 update panels on the page, a situation that I really wanted to avoid. Because the controls were inside the panel every partial postback I was losing the focus as effectively even though you don’t see it, the panel is destroyed and rebuilt every time.

So it became impossible for a user to just tab through the form updating values, as the focus was reset with every field, not an ideal user friendly situation.

So after much research I discovered that you can actually force focus to an individual control using the script manager control in the server side code. The code to do this is pretty simple, and would be something like:

Me.ScriptManager1.SetFocus(Textbox1)

Where scriptmanager1 is the name of your script manager control and textbox1 is the name of the control you want to set the focus too.

Now this is fine if you always know which control should have the focus, however if you have a lot of controls being processed inside one update panel you might not know which control to focus on next. Thankfully I found a neat little javascript on this blog http://couldbedone.blogspot.com/2007/08/restoring-lost-focus-in-update-panel.html That you can include with your script manager on any page, the javascipt will take care of all your focus problems for any update panels you have on your page. I’ll include the full script code below, don’t ask me to explain how it works, I’m just happy that it does and hope it will be of some use to you.

// JScript File

var lastFocusedControlId = "";

function focusHandler(e)

{

document.activeElement = e.originalTarget;

}

function appInit()

{

if (typeof(window.addEventListener) !== "undefined")

{

window.addEventListener("focus", focusHandler, true);

}

Sys.WebForms.PageRequestManager.getInstance().add_pageLoading(pageLoadingHandler);

Sys.WebForms.PageRequestManager.getInstance().add_pageLoaded(pageLoadedHandler);

}

function pageLoadingHandler(sender, args)

{

lastFocusedControlId = typeof(document.activeElement) === "undefined"

? "" : document.activeElement.id;}function focusControl(targetControl)

{

if (Sys.Browser.agent === Sys.Browser.InternetExplorer)

{

var focusTarget = targetControl;

if (focusTarget && (typeof(focusTarget.contentEditable) !== "undefined"))

{

oldContentEditableSetting = focusTarget.contentEditable;

focusTarget.contentEditable = false;

}

else

{

focusTarget = null;

}

targetControl.focus();

if (focusTarget)

{

focusTarget.contentEditable = oldContentEditableSetting;

}

}

else

{

targetControl.focus();

}

}

function pageLoadedHandler(sender, args)

{

if (typeof(lastFocusedControlId) !== "undefined" && lastFocusedControlId != "")

{

var newFocused = $get(lastFocusedControlId);

if (newFocused)

{

focusControl(newFocused);

}

}

}

Sys.Application.add_init(appInit);

This week I learned a handy little piece of sequel, which even though you probably already now about, I thought I would share it as I had not seen it before.

The Scenario

Say you had two tables, for example a customer table and an orders table. The tables were structured so that whenever an order was placed it was related to a particular customer through the ID. Pretty straightforward so far right? Well now say you wanted a list of all customers that have never had an order placed against them, so therefore no records will exist in the orders table.

Now I was going to approach this by doing all sorts of complicated outer joins, but then someone should be a much neater solution, it is the NOT IN clause which I had not come across before. So you basically say show me all records where table1’s ID is NOT IN table2. Below is an example using the tables I already mentioned.

SELECT cu.CustomerName,
Cu.CustomerID
FROM dbo.Customers cu
WHERE Cu.CustomerID NOT IN
(SELECT CustomerID FROM dbo.Orders)

Pretty simple eh, and works like a charm. Hope this will be as helpful to someone out there as it was to me.

I just had a technical interview for a developer contract and I feel the need to post about it because I really couldn’t see the point of the interview. I know that the interview went staggeringly badly, as I did struggle with a lot of the questions. Now that is of course my fault, but I just find myself annoyed at the questions themselves.

Now if I was interested in hiring a contractor, I would be very interested in knowing what real world experience that person has with writing websites. I would want to know about their history, about them personally, about what they want out of the contract etc. I would be very interested in examples of their work that they could demonstrate.

What I wouldn’t do is bombard them with a string of ridiculously low level questions and ask them nothing else at all. Who cares if I can explain from memory every single event that is triggered in order when a datagrid is loaded? What differences does it make? Do you want a developer with a wealth of real word experience in designing a living multi-tiered web application or do you want a walking encyclopaedia on .Net.

The answer in this case was clearly the latter, so I know I won’t get the contract and how I feel right now I’m not overly bothered that I won’t.