ComboBox By: Pall Bjornsson Categories: Selection

Tags: Architects, Developers, 1. Beginner, 2. Intermediate, 3. Advanced, Pre v6.3, v6.3, v6.4 and Later Revision: 1 Posted: 11/July/2009 Updated: 04/Dec/2010 Status: Publish Types: Reference

Overview

The ComboBox control is functionally equivialent to the Windows Forms ComboBox control and it displays a text box combined with a listbox, which enables the user to select items from the list or enter a new value.

The list of available items to select from can be built manually through the Items collection, or by using the DataSource property and assigning a DataSource of some kind.

Availability

The ComboBox is one of the Out of the Box standard controls, which means it is free and available in all Visual WebGui versions.

Relevant membersProperties

Name	Description
Items	A collection of items to select from . When populating the control manually, you will use this collection to add your items.
DataSource	Any list that implements IListor IListSourceinterfaces. ArrayListbeing one of the typical lists that can be assigned here.
DisplayMember	When using DataSource, then property (field) within the DataSource that should display in the list of available values.
ValueMember	When using DataSource, then property (field) within the DataSource that represents the value of the currently selected item.
SelectedIndex	The sequential index of the currently selected item within it's source list (manual or DataSource)
SeletedItem	The currently selected item. The type of this property varies, depending on the type of datasource in use. No DataSource nothing (use SelectedValue) DataSource is DataTable System.Data.DataRowView DataSource is BindingSource System.Data.DataRowView DataSource is any other IList or IListSource An item from that datasource
SelectedValue	The value of the currently selected item. If using the ComboBox without DataSource, then simply the item from the manually populated list. If using DataSource, then the property from the DataSource set in the ValueMember property above (defaults to ToString() if not set).

Samples of use

• Populating with List of KeyValuePair objects
  
• Populating with Employees from Northwind SQL sample database
  
• Populating two ComboBoxes where contents of second depend on first
• Populating multiple ComboBoxes that all use the same DataSource
• Skinable (custom) combobox automatically dropping down on focus

Limitations and workarounds

• 6.3.x IE security settings preventing dropdowns from working

RererencesArticles

• Handling huge datasets on web as easy as desktop

Code samples

• Create a custom multicolumn ComboBox
• Using OnPropertyChange databindings
• Control of a ComboBox with a CheckedList and a Tree
• ComboBox AutoComplete sample

Forum discussons

• Ideas for ComboBox allowing only digits
  
• Assigning ContextMenu in constructor may "disturb" serialization

Other references

• MSDN Windows Forms ComboBox documenation
• Bound to BindingSource ComboBox does not update it's bound source til you call EndEdit

About the author

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