Class ComboBoxBase

An advanced combo box control.

Inheritance
System.Object
ComboDropDown
ComboBoxBase
ColorComboBox
RTLComboBoxBase
ComboBoxBaseDataBound
ComboBoxExt
Implements
System.ComponentModel.ISupportInitialize
Inherited Members
Namespace: Syncfusion.Windows.Forms.Tools
Assembly: Syncfusion.Shared.Base.dll
Syntax
public class ComboBoxBase : ComboDropDown, IThemedControl, ISupportInitialize, INonClientPaintingSupport, ISupportOffice2007Theme, IVisualStyle
Remarks

This advanced combo box control provides a lot of improvements over the standard System.Windows.Forms.ComboBox control. The improvements are as follows:

  • Plug in any System.Windows.Forms.ListControl derived class as the list for the list portion of the combo box using the ListControl property.
  • Provides a System.Windows.Forms.FlatStyle mode for regular, flat or themed drawing.
  • Written using native .NET controls, this control lets you customize everything in the combo box from the textbox to the drop-down window.

This control requires the plugged in ListControl to implement the Items property returning a valid System.Collections.IList instance. The ListControl can optionally implement an IndexFromPoint method that will take a single argument of type System.Drawing.Point and a TopIndex property of type int. The semantics of these above properties and methods are similar to that of a System.Windows.Forms.ListBox's implementation.

Implementing IndexFromPoint and TopIndex will enable QuickSelection capability for the combo box, wherein the user can click on the drop-down button and start selecting items in the list, all this without releasing the mouse.

Constructors

ComboBoxBase()

Creates a new instance of the ComboBoxBase class.

Declaration
public ComboBoxBase()
Remarks

Initializing this ComboBoxBase also requires you to set the ListControl property of this combo box.

Properties

AutoComplete

Gets a value indicating whether the control uses AutoComplete.

Declaration
public bool AutoComplete { get; set; }
Property Value
Type
System.Boolean

ListControl

Gets or sets the System.Windows.Forms.ListControl that will be used in the drop-down portion.

Declaration
public virtual ListControl ListControl { get; set; }
Property Value
Type Description
System.Windows.Forms.ListControl

A System.Windows.Forms.ListControl derived instance.
Remarks

Take a look at the ComboBoxBase class description for more information on requirements and usage of this list control.

PopupControl

This will be used in the drop-down portion.

Declaration
public override Control PopupControl { get; set; }
Property Value
Type
System.Windows.Forms.Control
Overrides

UpdateSelectionBeforeValidate

Indicates whether the selection in the list control should be updated with the new text entered by the user when the control loses focus.

Declaration
public virtual bool UpdateSelectionBeforeValidate { get; set; }
Property Value
Type
System.Boolean
Remarks

This property is typically used only when the list mode is set to editable (DropDown).

Methods

AttachPopupControl()

Called when a new System.Windows.Forms.ListControl gets attached to this ComboBoxBase using the ListControl property.

Declaration
protected override void AttachPopupControl()
Overrides
Remarks

When you override this method, make sure to call the base class for proper initialization.

CorrectPopupLocation(Point)

Correct popup control location.

Declaration
protected virtual Point CorrectPopupLocation(Point location)
Parameters
Type Name Description
System.Drawing.Point location
Returns
Type
System.Drawing.Point

CreateAccessibilityInstance()

Declaration
protected override AccessibleObject CreateAccessibilityInstance()
Returns
Type
System.Windows.Forms.AccessibleObject
Overrides

CreatePopupContainer()

Declaration
protected override PopupControlContainer CreatePopupContainer()
Returns
Type
PopupControlContainer
Overrides

DetachPopupControl(Boolean)

Called when an attached System.Windows.Forms.ListControl is being detached from this combo.

Declaration
protected override void DetachPopupControl(bool disposing)
Parameters
Type Name Description
System.Boolean disposing

Indicates whether this method is called from Dispose.
Overrides

Dispose(Boolean)

Declaration
protected override void Dispose(bool disposing)
Parameters
Type Name Description
System.Boolean disposing
Overrides

FindItem(String, Boolean, Int32, Boolean)

Called to find a matching item in the attached ListControl given the prefix of the item.

Declaration
protected override int FindItem(string prefix, bool select, int start, bool ignoreCase)
Parameters
Type Name Description
System.String prefix

The prefix string.
System.Boolean select

Indicates whether to change the selection in the list when a match occurs.
System.Int32 start

The index within each list item-string, where the search begins.
System.Boolean ignoreCase

Indicates whether to ignore case.
Returns
Type Description
System.Int32

The index of the matching item; -1 otherwise.
Overrides

GetIndexFromPoint(Point)

Returns the index of the item at the specified point.

Declaration
protected virtual int GetIndexFromPoint(Point pointScreen)
Parameters
Type Name Description
System.Drawing.Point pointScreen

A System.Drawing.Point in screen coordinates.
Returns
Type Description
System.Int32

The zero based index; -1 if the point is not over an item.

GetListControlList()

Returns the System.Collections.IList interface representing the item's collection of the attached ListControl.

Declaration
protected virtual IList GetListControlList()
Returns
Type Description
System.Collections.IList

An IList interface.
Remarks

The base class version looks for the "Items" property in the attached ListControl.

GetPopupControlItemText(Int32)

Returns the text representation of the specified item in PopUpControl.

Declaration
protected override string GetPopupControlItemText(int index)
Parameters
Type Name Description
System.Int32 index

The index.
Returns
Type
System.String
Overrides

GetPopupControlListControl()

Declaration
protected virtual ListControl GetPopupControlListControl()
Returns
Type
System.Windows.Forms.ListControl

HasListInterface()

Declaration
protected override bool HasListInterface()
Returns
Type
System.Boolean
Overrides

IsIndexFromPointAvaillable()

Indicates whether the attached ListControl has an "IndexFromPoint" method.

Declaration
protected virtual bool IsIndexFromPointAvaillable()
Returns
Type Description
System.Boolean

True if such a method is available; False otherwise.
Remarks

This control relies on the attached ListControl providing this method to support quick-selection mode. This is the mode where the user can click on the drop-down arrow and start selecting in the drop-down list even before mouse up.

IsTextValid(String)

Indicates whether the supplied text is a valid entry in the attached ListControl.

Declaration
protected override bool IsTextValid(string text)
Parameters
Type Name Description
System.String text

The text to validate.
Returns
Type Description
System.Boolean

True if valid; False otherwise.
Overrides

IsValidIndex(Int32)

Indicate whether ListControl contains item with such index.

Declaration
protected override bool IsValidIndex(int index)
Parameters
Type Name Description
System.Int32 index

The index.
Returns
Type Description
System.Boolean

True - if there is such item, otherwise - false.
Overrides

MoveSelelctionInPopupControl(Boolean)

Moves the current selection in the attached ListControl.

Declaration
protected override void MoveSelelctionInPopupControl(bool up)
Parameters
Type Name Description
System.Boolean up

Indicates whether to move up.
Overrides

OnAutoCompleteChanged()

Declaration
protected virtual void OnAutoCompleteChanged()

OnBeforePopup()

Called before the popup gets dropped down.

Declaration
protected override void OnBeforePopup()
Overrides

OnDropDownCloseOnClick(MouseClickCancelEventArgs)

Raises the DropDownCloseOnClick event.

Declaration
protected virtual void OnDropDownCloseOnClick(MouseClickCancelEventArgs args)
Parameters
Type Name Description
MouseClickCancelEventArgs args

A MouseClickCancelEventArgs that contains the event data.
Remarks

Raising an event invokes the event handler through a delegate. For more information, see Raising an Event.

The OnDropDownCloseOnClick method also allows derived classes to handle the event without attaching a delegate. This is the preferred technique for handling the event in a derived class.

Note to Inheritors: When overriding OnDropDownCloseOnClick in a derived class, be sure to call the base class's OnDropDownCloseOnClick method so that registered delegates receive the event.

OnEndInit()

Declaration
protected override void OnEndInit()
Overrides

OnHandleCreated(EventArgs)

Declaration
protected override void OnHandleCreated(EventArgs e)
Parameters
Type Name Description
System.EventArgs e
Overrides

OnListMouseUp(MouseEventArgs)

Called when the user clicks on the associated list box.

Declaration
protected virtual void OnListMouseUp(MouseEventArgs e)
Parameters
Type Name Description
System.Windows.Forms.MouseEventArgs e

The MouseEventArgs from the list box's MouseUp event.

OnListSelectedValueChangedWhileNotShowingPopup(Int32)

Declaration
protected virtual void OnListSelectedValueChangedWhileNotShowingPopup(int newIndex)
Parameters
Type Name Description
System.Int32 newIndex

OnMouseUpOnQuickSelect()

Handles the PopupCloseType of PopUpContainer based on SelectedIndex.

Declaration
protected override void OnMouseUpOnQuickSelect()
Overrides

OnNoChangeDetectedOnPopupClosed()

Declaration
protected override void OnNoChangeDetectedOnPopupClosed()
Overrides

OnSelectedIndexChanging(SelectedIndexChangingArgs)

Fires SelectedIndexChanging event.

Declaration
protected virtual void OnSelectedIndexChanging(SelectedIndexChangingArgs e)
Parameters
Type Name Description
SelectedIndexChangingArgs e

OnSelectionChangedByKey()

Declaration
protected virtual void OnSelectionChangedByKey()

OnUpdateSelectionBeforeValidate()

Called to update selection before validate.

Declaration
protected virtual void OnUpdateSelectionBeforeValidate()
Remarks

This is useful when you enable auto completion in the text area and force the list box's SelectedValue to be updated to the latest text value in this control's Validated event.

OnValidating(CancelEventArgs)

Raises the Validating event.

Declaration
protected override void OnValidating(CancelEventArgs e)
Parameters
Type Name Description
System.ComponentModel.CancelEventArgs e

PerformTextAutoComplete(KeyPressEventArgs)

Declaration
protected override void PerformTextAutoComplete(KeyPressEventArgs e)
Parameters
Type Name Description
System.Windows.Forms.KeyPressEventArgs e
Overrides

ProcessListMouseMove(Object, MouseEventArgs)

Processes mouse move over the list.

Declaration
protected virtual void ProcessListMouseMove(object sender, MouseEventArgs e)
Parameters
Type Name Description
System.Object sender

The control source of the MouseMove event.
System.Windows.Forms.MouseEventArgs e

The event args of the MouseMove event.
Remarks

This method moves the selection of the attached ListControl in some cases when the mouse moves over it and also to change the Top Index of the list control appropriately when QuickSelection is on.

ProcessPopupControlMouseMove(Object, MouseEventArgs)

Processes the mouse move over the PopupControl.

Declaration
protected override void ProcessPopupControlMouseMove(object sender, MouseEventArgs e)
Parameters
Type Name Description
System.Object sender
System.Windows.Forms.MouseEventArgs e
Overrides

SetPopupText(String)

Sets the popup text.

Declaration
protected override void SetPopupText(string value)
Parameters
Type Name Description
System.String value

The value.
Overrides
Remarks

Compares the new PopUpText and resets if a match is not found.

WndProc(ref Message)

Declaration
protected override void WndProc(ref Message m)
Parameters
Type Name Description
System.Windows.Forms.Message m
Overrides

Events

AutoCompleteChanged

Risen by OnAutoCompleteChanged() method.

Declaration
public event EventHandler AutoCompleteChanged
Event Type
Type
System.EventHandler

DropDownCloseOnClick

Occurs when the user clicks in the list box in the drop-down to let you cancel the subsequent drop-down close.

Declaration
public event MouseClickCancelEventHandler DropDownCloseOnClick
Event Type
Type
MouseClickCancelEventHandler

SelectedIndexChanging

Occurs when the selected Index of list is about to be changed. Can be canceled to avoid selection of the specific item.

Declaration
public event SelectedIndexChangingHandler SelectedIndexChanging
Event Type
Type
SelectedIndexChangingHandler

Implements

System.ComponentModel.ISupportInitialize