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Read only ComboBox

, 11 Oct 2004
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How to make ComboBox read only


Surprisingly the MS Visual Studio ComboBox doesn’t have such an important property: ReadOnly. After searching on internet for solving this problem and not finding a relevant resolution I decided to add this important property to a new ComboBox control.

Using the code

Create a new derived class from ComboBox:

public class NewComboBox    : System.Windows.Forms.ComboBox

Declare private variables:

private bool readOnly;
private Color tBackColor;
private Color tForeColor;
private ContextMenu cmnuEmpty;
private ComboBoxStyle dropDownStyle = ComboBoxStyle.DropDown;
private Color readOnlyBackColor = SystemColors.Control;
private Color readOnlyForeColor = SystemColors.WindowText;

Set custom context menu to be display when read only:

public ReadOnlyComboBox()
  cmnuEmpty = new ContextMenu(); //code this menu for your needs

Declare ReadOnly property:

public bool ReadOnly
    return readOnly;
    if(readOnly != value)
      readOnly = value;
        this.ContextMenu = cmnuEmpty;
        base.DropDownStyle = ComboBoxStyle.Simple;
        base.Height = 21;
        this.tBackColor = this.BackColor;
        this.tForeColor = this.ForeColor;
        base.BackColor = this.ReadOnlyBackColor;
        base.ForeColor = this.ReadOnlyForeColor;
        this.ContextMenu = null;
        base.DropDownStyle = dropDownStyle;
        base.BackColor = tBackColor;
        base.ForeColor = tForeColor;

Override OnKeyDown and OnKeyPress events to stop editing when readonly:

protected override void OnKeyDown(KeyEventArgs e)  
  if(this.ReadOnly && (
    e.KeyCode == Keys.Up  || 
    e.KeyCode == Keys.Down  ||
    e.KeyCode == Keys.Delete))
    e.Handled = true;
    base.OnKeyDown (e);

protected override void OnKeyPress(KeyPressEventArgs e) 
        e.Handled = true;
        base.OnKeyPress (e);

Change the DropDownStyle property to reflect property changes only when not ReadOnly:

new public ComboBoxStyle DropDownStyle
    return dropDownStyle;
    if(dropDownStyle != value)
      dropDownStyle = value;
      if(!this.ReadOnly) base.DropDownStyle = value;

Add back/fore color properties to reflect changes in ReadOnly property:

public Color ReadOnlyBackColor
    return readOnlyBackColor;
    readOnlyBackColor = value;
public Color ReadOnlyForeColor
    return readOnlyForeColor;
    readOnlyForeColor = value;


Eliminate the white border that appears inside the client area when enable XP styles and BackColor is not default color.


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About the Author

Software Developer (Senior)
Romania Romania
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Comments and Discussions

GeneralMust also disable mouse paste PinmemberFinishedOnTime26-Feb-07 4:25 
QuestionLatest code? PinmemberChuck_Esterbrook27-Dec-06 14:43 
GeneralKeyPress Event Handler Pinmemberjsteve1712-Dec-06 10:16 
GeneralVery good. Pinmemberjotaele31-Oct-06 0:00 
QuestionHow to remove the white border? Pinmembersick bastard1-Jan-06 22:59 
GeneralAnother approach for a ReadOnly ComboBox PinmemberClaudio Grazioli9-May-05 11:12 
GeneralRe: Another approach for a ReadOnly ComboBox PinmemberChuck_Esterbrook27-Dec-06 13:35 
GeneralToo bad.... Pinmemberemunews28-Feb-05 3:48 
GeneralReadOnlyComboBox in DropDownList Mode Pinmemberpgolds6-Dec-04 6:21 
GeneralRe: ReadOnlyComboBox in DropDownList Mode Pinmemberpgolds6-Dec-04 8:22 
GeneralRe: ReadOnlyComboBox in DropDownList Mode PinmemberDan Anatoli6-Dec-04 20:30 
GeneralRe: ReadOnlyComboBox in DropDownList Mode Pinmemberpgolds7-Dec-04 5:34 
GeneralOptional solution Pinmemberomacias20-Nov-04 9:43 
GeneralRe: Optional solution PinsussAnonymous21-Nov-04 1:02 
GeneralThank You. Pinmemberpgolds19-Nov-04 10:33 
GeneralRefreshing a DropDownList PinmemberPaco7612-Nov-04 8:31 
GeneralNice. One little remark. PinmemberBoyan Botev19-Oct-04 22:14 
GeneralRMB option cut enabled Pinmemberasela.gunawardena@ifs.lk5-Oct-04 1:03 
GeneralRe: RMB option cut enabled PinmemberDan Anatoli5-Oct-04 20:22 
GeneralRe: RMB option cut enabled PinmemberAsela Gunawardena25-Oct-04 0:56 
GeneralRe: Re: RMB option cut enabled PinmemberAsela Gunawardena25-Oct-04 0:58 
QuestionWhy not just change the DropDownStyle Property? PinsussAnonymous30-May-04 8:11 
AnswerRe: Why not just change the DropDownStyle Property? PinmemberDan Anatoli30-May-04 19:57 
GeneralDropDownList can open, but selection can't be changed. PinmemberHanan Nachmany25-Apr-04 2:35 
GeneralCombobox still recieves F4, PageDown and pageUp PinmemberGuemper17-Mar-04 21:11 
GeneralRe: Combobox still recieves F4, PageDown and pageUp PinmemberDan Anatoli18-Mar-04 19:23 
GeneralRe: Combobox still recieves F4, PageDown and pageUp Pinmemberedokan3-May-04 7:20 
General...and you can cut the text PinmemberMarcuse726-May-04 6:14 
GeneralRe: ...and you can cut the text PinmemberDan Anatoli31-May-04 0:02 
GeneralThat's the hard way... PinmemberRay Hayes12-Mar-04 5:02 
GeneralRe: That's the hard way... PinmemberDan Anatoli14-Mar-04 19:50 
GeneralThe easiest way.. Pinmemberyltsa25-Mar-05 22:28 
GeneralRe: That's the hard way... PinmemberSystem.Object21-Apr-06 10:29 
QuestionHOW to add this NewComboBox to the form? PinmemberNappo2310-Mar-04 9:21 
AnswerRe: HOW to add this NewComboBox to the form? PinmemberDan Anatoli10-Mar-04 20:48 
GeneralCombox the worst control PinmemberElNoNo10-Mar-04 4:44 
GeneralRe: Combox the worst control PinmemberRoger J10-Mar-04 4:52 
GeneralRe: Combox the worst control PinmemberSebCode11-Oct-04 4:44 
QuestionDropDownList? PinsitebuilderUwe Keim9-Mar-04 7:31 
AnswerRe: DropDownList? PinmemberDan Anatoli9-Mar-04 19:50 
GeneralRe: DropDownList? Pinmemberstringali6911-Mar-04 6:13 
GeneralRe: DropDownList? PinmemberDan Anatoli11-Mar-04 19:46 
GeneralRe: DropDownList? PinsussAnonymous15-Aug-04 22:09 
GeneralRe: DropDownList? PinmemberDan Anatoli16-Aug-04 1:52 

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