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Master Page Error

If you're like me you may have gone into design mode in visual studio 2010 hoping to do some work only to be greeted with the following message.

Which initially is a bit confusing, as your site may have just run without any problems. But even so you go to check the placeholders anyway and they look fine. Then you copy and paste the ID's out of the Master Page just to be sure, but still no luck. Check through the Master Page itself and that also looks fine, no squiggly lines to be seen. Finally create a new WebForm linked to the master page, but even this gives the same error.

Now if you have the problem I had, look at the title tag in the Master Page. Does it say <title /> or <title></title>? If it's the first then that's your issue. By default VS2010 will put in the correct tag, but if like me you've just slapped in some HTML from an old project or from a PSD conversion that's been done for you, then chances are you may end up overwriting the title tag as well.

.Net Tip: Default Button for Enter Key

I don't know if I should be happy to now know about this, or just concerned that it's taken me this long to discover. But one issue that surfaces time and time again when programming in ASP.NET, is that issue that pressing enter/return in a text field doesn't always do what you want it to do. 

On a normal website you can have many forms each with their own submit button which becomes the default action when pressing return on one of the forms fields. However in ASP.NET Web Forms there is only ever one form on a page, but there could be 10 different buttons each needing to be the default action for a particular text box. 

The solution as it turns out is very simple and you have two options both introduced in .NET 2.0 (yes that's how old it is!) 

1. Default button for the form. If your page has more than one button, but there is only one that you want to fire when you hit enter then in the code behind you can just type... 

1Form.DefaultButton = Button1

or it can also be specified in your aspx file 

1<form runat="server" defaultbutton="Button1">

2. If you need to be more specific a panel can also have a default button... 

1Panel1.DefaultButton = Button1
2

3<asp:Panel runat="server" DefaultButton="Button1">
Hot Keys Made Simple

Hot Keys Made Simple

Previously I have blogged about how you can create keyboard shortcuts using JavaScript. In other words being able to add functionality to your web app for someone to do a ctrl+s. My previous example wasn't particularly hard and only used 10 lines of code, but this week I stumbled across a jQuery plugin that makes it easier.

http://code.google.com/p/js-hotkeys/

With this plugin, in just 1 line of code you can bind a function to a keyboard shortcut. What's more you don't even need to look up the correct keycodes as it takes a simple text parameters.

1$(document).bind('keydown', 'ctrl+c', fn);

Combine this with a function that just triggers a button click and you have some very cool advanced looking functionality written in around 5 - 10 minuets.

Creating Events in ASP.NET

Creating your own events on your own controls is something that is essential if you want you web app to work well and also provide you with reusable controls. It's easy to skip past the problem and find another way to get your code to do what you want it to do and detect the change another way. But you end up with much nicer code if your controls can have proper events for a piece of action, and you web page can have proper event handlers on each. Not only that but the code you need to write in generally a copy and past job and not that hard.

The Code

While it's not that hard, the amount of code that is needed is quite a lot more than you may expect. Fortunately though it's code you going to just re-use again and again changing small bits as needed.

1//1 - Event args (use default, but eventually pass in data through here)
2public class SaveCompleteEventArgs : EventArgs
3{
4    public SaveCompleteEventArgs(int inDataValue)
5    {
6        this.DataValue = inDataValue;
7    } //end of con
8 
9    public readonly int DataValue;
10}
11 
12//2 - define delegate
13public delegate void SaveCompleteEventHandler(object sender, SaveCompleteEventArgs e);
14 
15//3 - define the event itself
16public event SaveCompleteEventHandler SaveComplete;
17 
18//4 - the protected virtual method to notify registered objects of the request
19//  virtual so that it can be overridden.
20protected virtual void OnSaveComplete(SaveCompleteEventArgs e)
21{
22    //if the UpdateData event is empty, then a delegate has not been added to it yet.
23    if (SaveComplete != null)
24    {
25        //event exists, call it:
26        SaveComplete(this, e);
27    } //end of if
28}
29 
30//5 - method that translates the input into the desired event
31public void TriggeringMethod(int strData)
32{
33 
34    // get new event args
35    //EventArgs e = new EventArgs();
36    SaveCompleteEventArgs e = new SaveCompleteEventArgs(strData);
37 
38    // call the virtual method
39    OnSaveComplete(e);
40}