Silverlight Combobox that handles key press

06-14-2009 12:36 PM |

Hey all,

Does anyone have a class that extends ComboBox that handles selection of items by pressing a key? And no, I don't want to use the AutoCompleteBox. I'm basically just looking for a ComboBox that works like the html one (which is how the built-in one should behave.) Let's say we have a state dropdown, when you press m it might select Maryland, then when you press m again it might select Massachusetts. I have one that works right now but it only works for the first time you press a letter, I couldn't figure out a way to select the next items with that letter.

Here's the code I have so far:

http://pastebin.com/m72da0672

 I figure many people have already tackled this problem so didn't want to reinvent the wheel. I'm using SL3 beta if it makes a difference. Thanks for any help...

Re: Silverlight Combobox that handles key press

06-19-2009 10:06 PM |

:: bump ::

Re: Silverlight Combobox that handles key press

06-20-2009 2:15 PM |

I raised this issue a while back in Silverlight 2, and was hoping it would be fixed in Silverlight 3, but the beta didn't get my hopes up. I know they are targetting LOB apps for Silverlight 3, and this deficiency makes the ComboBox almost unuseable. I really don't understand how it got this far like this; it's like the developers of the ComboBox have no idea how a ComboBox is supposed to work.

Re: Silverlight Combobox that handles key press

06-20-2009 3:22 PM |

The silverlight combobox does not behave like a regular combobox, because it shouldnt.

Since in ASP, MFC, WinForms all Comboboxes can only contain strings you can actually perform string access operations inside them, theres no harm in doing so.

The Silverlight and WPF Combobox does not have this limitation and can consist of complex visual elements on the presentation side and complex classes on the data side.

Since there is no guarantee, that somewhere within this complex structure is actually a string that will be used as the SelectedValuePath, it would be mostly unwise to bloat the combobox with features that do only work in certain situations and environments.

So no, you have to implement those feature by urself.

private index = 0;
private lastKey = Keys.Escape; // or something which i not used often
private IList<string> list;

OnComboboxKeyUp(DependencyObject sender, KeyEventArgs e)
{
     if(e.Key != lastKey)
     {
         list = // get all entries starting with the letter represented by e.Key from the itemssource
         index = 0;
     }
     else
     { 
         index++;
         // check if out of bounce, return to 0 if true
     }
     ComboBox.SelectedValue = list[index];
}

I just typed this down without testing but it should give you an idea

Re: Re: Silverlight Combobox that handles key press

06-20-2009 5:09 PM |

I completely disagree... Even if it's bound to a collection of business objects, 9 times out of 10 the DisplayMemberPath is going to be a string. They could easily provide this functionality so long as that property is a string. Alternately, you could have a property for enabling it, which would throw an exception if DisplayMemberPath is not a string property of the business object.

You end up making every developer face the same issue, which either cuts down productivity, or if you choose to ignore it, cuts down the usability of your application. The fact of the matter is that end-users expect the dropdown to behave the same in Silverlight as it would in an html web application. It's one thing if the Silverlight combobox does more than the html one, but for it to do less is unacceptable.

Thanks for the code sample, I'll try it out later.

Re: Re: Silverlight Combobox that handles key press

06-21-2009 12:23 AM |

OK I'm obviously going to give the points to the guy who agrees with me, no hard feelings. :)