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3.6. Create Text Boxes thatAuto-Complete
In many of the nooks and crannies of
the Windows operating system, you'll find
AutoComplete text boxes. These text boxes suggest one or more values
as you type.
Note: With . NET's new auto-complete features,
you can create intelligent text boxes able to suggest possible values
based on recent entries or a default list.
Usually, AutoComplete values are drawn from your recent history. For
example, when you type a URL into Internet
Explorer's address bar, you'll see
a list that includes URLs you've surfed to in the
past. Now with .NET 2.0, you can harness the same AutoComplete
features with your own custom lists or one of the lists maintained by
the operating system.
3.6.1. How do I do that?
The TextBox and the ComboBox
controls both support the AutoComplete feature in .NET 2.0. To use
AutoComplete, first set the control's
AutoCompleteMode
property to one of the following values:Append
In this mode, the AutoComplete value is automatically inserted into
the control as you type. However, the added portion is selected so
that the new portion will be replaced if you continue typing.
(Alternatively, you can just click delete to remove it.)
Suggest
This is the friendliest mode. As you type, a drop-down list of
matching AutoComplete values appears underneath the control. If one
of these entries matches what you want, you can select it.
SuggestAppend
This mode combines Append and
Suggest. As with Suggest, a
list of candidate matches is shown in a drop-down list. However, the
first match is also inserted into the control and selected.
After choosing the type of AutoComplete, you need to specify what
list will be used for suggestions. Do this by setting the
AutoCompleteSource
property to one of the following values:FileSystem
Includes recently entered file paths. Use
FileSystemDirectories instead to include only
directory paths.
HistoryList
Includes URLs from Internet Explorer's history list.
RecentlyUsedList
Includes all the documents in the user's
"most recently used list," which
appears in the Start menu (depending on system settings).
AllUrl
Includes the URLs of all sites that the current user has visited
recently, whether they were typed in manually by the user or linked
to from a web page.
AllSystemSources
Includes the full list of URLs and file paths.
ListItems
Includes the items in the ComboBox.Items
collection. This choice isn't valid with the
TextBox.
CustomSource
Includes the items in the AutoCompleteCustomSource
collection. You need to add these items yourself.
Figure 3-8 shows an AutoComplete text box using
AutoSuggestAppend as the
AutoCompleteMode and AllUrl as
the AutoCompleteSource.
Figure 3-8. An AutoComplete text box
controls both provide the same functionality. If you use
AutoSuggest or
AutoSuggestAppend with a
ComboBox, the list of matches is displayed in a
list under the control. However, this list shouldn't
be confused with the list of entries that you've
added to the ComboBox.Items property. When you
click the drop-down arrow for the ComboBox,
you'll see your list of items,
not the list of AutoComplete suggestions. Both
lists are completely separate, and there is no programmatic way for
you to interact with the AutoComplete list. The only exception is if
you create a ComboBox with an
AutoCompleteSource of
CustomSource or ListItems.
3.6.2. What about...
...using AutoComplete in other controls? Unfortunately,
there's no managed way to do it in .NET. However,
you can retrieve the information you need directly from the registry.
For example, if you look in the Software\Microsoft\Internet
Explorer\TypedURLs section of the
HKEY_CURRENT_USER registry key,
you'll find the list of recently typed in URLs. To
retrieve these items programmatically, refer to classes like the
RegistryKey in the
Microsoft.Win32 namespace.
