Customizable ComboBox Drop-Down

Lea Hayes

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20 Nov 2014MIT3 min read

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A combobox control with a customizable drop-down

Version 2.2:
- Download demo project (Version 2.2) - 39.18 KB
- Download source (Version 2.2) - 8.2 KB
Version 1:
- Download demo project (Version 1) - 45.75 KB
- Download source (Version 1) - 3.87 KB

Introduction

This article presents an extension of the .NET ComboBox which provides custom drop-downs. The control can automatically add a resizer grip at the bottom of a drop-down.

Design

Custom drop-down functionality can be achieved using the .NET ToolStripDropDown and ToolStripControlHost classes. These two classes are great because they prevent application forms from becoming inactive during drop-down. The custom popup functionality required by this control has been encapsulated within the class PopupControl (a new addition since the original article posting).

In addition to facilitating this control, the PopupControl class can be used to provide drop-down support in your own controls. The PopupControl also integrates the drop-down resize support (now without the need for a nested resizable container, see below for details).

Previously the drop-down control was resizable by nesting a resizable container. This was an okay solution (because it worked) but it caused some redraw errors during resize operations. The resize functionality has now been significantly improved, and it is now also possible to define which sides of the drop-down are resizable (if any). Resizing can now also be done by dragging the resizable edges of the drop-down. The new resize functionality is achieved by intercepting Win32 hit testing messages, and responding appropriately based upon the set PopupResizeMode property.

The following UML class diagram provides an overview of the presented classes:

Using the Code

As with most controls, this control can be created dynamically at runtime, or by using the Visual C# IDE designer's drag and drop features. During runtime, the property DropDownControl must be assigned to an instance of another control. The assigned control must not be contained elsewhere as this will cause problems.

Most drop-down controls appear better when their borders are removed.

namespace CustomComboDemo
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            // Dynamically created controls.

            // Create grid view control.
            DataGridView gridView = new DataGridView();
            gridView.BorderStyle = BorderStyle.None;
            gridView.Columns.Add("Column1", "Column 1");
            gridView.Columns.Add("Column2", "Column 2");
            gridView.Columns.Add("Column3", "Column 3");
            gridView.Columns.Add("Column4", "Column 4");
            gridView.Columns.Add("Column5", "Column 5");
            this.customComboBox1.DropDownControl = gridView;

            // Create user control.
            UserControl1 userControl = new UserControl1();
            userControl.BorderStyle = BorderStyle.None;
            this.customComboBox2.DropDownControl = userControl;

            // Create rich textbox control.
            RichTextBox richTextBox = new RichTextBox();
            richTextBox.BorderStyle = BorderStyle.None;
            this.customComboBox3.DropDownControl = richTextBox;
        }
    }
}

Points of Interest

When writing the code, I found that dropped-down controls were not retrieving immediate input focus. This problem occurs because even though the drop-down code is ignored during the Win32 message handler, the standard win32 drop-down still appears (1x1 pixels). To avoid this, a timer is created which forces the dropped-down control to be focused after the default win32 drop-down has been focused. Once the timer has done its job, it disables itself.

History

22^ndApril, 2008: Original version posted
29^thApril, 2008: Updated download files
- Fixed a bug that was pointed out by Adam Hearn
17^thJune, 2008: Various changes
- Improved design
- Odd drawing effects during drop-down resize have now been significantly improved
- Added PopupControl for general custom drop-down support
- Added download files: Version 2
28^th June, 2008: Updated download files for Version 2
15^th July, 2008: Updated to version 2.1.
- Many thanks to member “Leon v Wyk” for this update
- The improved version now hides incompatible properties from the Visual Studio .IDE properties panel which was causing confusion
21^st June, 2009: Updated to version 2.2
- Updated source, demo project and UML overview diagram
- Fixed bug found by CodeProject member “dokmanov”
  Whilst the “DropDownClosed” event was being fired when the drop down arrow was used to close the drop down, it was not being fired when the drop down was closed by clicking in the form area

License

This article, along with any associated source code and files, is licensed under The MIT License

Written By

Lea Hayes

Software Developer Rotorz Limited

United Kingdom

I have been fascinated by software and video games since a young age when I was given my first computer, a Dragon 32. Since then I have experimented with numerous methods of development ranging from point-and-click type packages to C++. I soon realized that software development was what I wanted to do.

Having invested a lot of time into programming with various languages and technologies I now find it quite easy to pickup new ideas and methodologies. I relish learning new ideas and concepts.

Throughout my life I have dabbled in game and engine development. I was awarded a first for the degree "BEng Games and Entertainment Systems Software Engineering" at the University of Greenwich. It was good to finally experience video games from a more professional perspective.

Due to various family difficulties I was unable to immediately pursue any sort of software development career. This didn't stop me from dabbling though!

Since then I formed a company to focus upon client projects. Up until now the company has primarily dealt with website design and development. I have since decided that it would be fun to go back to my roots and develop games and tools that other developers can use for their games.

We have recently released our first game on iPhone/iPad called "Munchy Bunny!" (see: http://itunes.apple.com/us/app/munchy-bunny!/id516575993?mt=8). We hope to expand the game and release to additional platforms.

Also, check out our tile system extension for Unity! (see: http://rotorz.com/tilesystem/)

Comments and Discussions

Re: DropDownClosed event not firing

Lea Hayes19-Jun-09 21:40

Lea Hayes

19-Jun-09 21:40

Hi,

Did you get my email? I sent you the ZIP file to your Yahoo account as you requested.

Re: DropDownClosed event not firing

dokmanov20-Jun-09 17:48

dokmanov

20-Jun-09 17:48

Yep!

And it works now!

Very nice! Thank you!

Re: DropDownClosed event not firing

Lea Hayes21-Jun-09 2:31

Lea Hayes

21-Jun-09 2:31

Excellent!

Thanks again for bringing this problem to my attention!

Re: DropDownClosed event not firing

Lea Hayes21-Jun-09 12:52

Lea Hayes

21-Jun-09 12:52

The latest corrected version is now available from CodeProject.

Thanks again!

Re: DropDownClosed event not firing

debajyoti2005in8-Jul-09 23:34

debajyoti2005in

8-Jul-09 23:34

i got an error Error 1 'CustomComboBox.PopupControl.PopupControlHost.get' must declare a body because it is not marked abstract or extern C:\WindowsApplication1\WindowsApplication1\PopupControl.cs 758 52 WindowsApplication1
what is the solve for this .
am using vs2005

Re: DropDownClosed event not firing

Lea Hayes9-Jul-09 0:41

Lea Hayes

9-Jul-09 0:41

Hi,

Are you using the latest version of this control? I have updated the version that is available from CodeProject now.

Can you please provide steps that I can follow to reproduce the error?

Many thanks,
Lea Hayes

Using a ListBox?

metator25-Apr-09 9:33

metator

25-Apr-09 9:33

Hi there,

First of all, i would like to say that i find this custom combobox really great and useful. But i think there's one thing it cannot do (or it seems really hard to do it). I'm trying to use this control to implement a real combobox using a listbox as the hosted control. What i want is to reutilize the size grip feature and, at the same time, maintain all the normal combobox functionality. So, in this scenario, hiding those "unwanted" properties will not help me at all. If i unhide them, the control might not be reusable in other scenarios. I'm also having trouble to mimic the combobox events - it doesn't fire when it is expected to.

My question is: is it possible to use your control in this scenario? Is there any other way where i can have a combobox dropdown with a size grip (using the DropdownList Style)? I know a normal combobox will only show a grip when using the AutoComplete feature, but i want to show the grip always.

Thanks in advanced.

You realize that everything you learn is in fact just learned, not necessarily true...

Re: Using a ListBox?

Lea Hayes26-Apr-09 15:35

Lea Hayes

26-Apr-09 15:35

Hi,

I am glad that you have found my combo box control useful!

One solution might be to create a new control with a name like "ListComboBox" which:

1. Constructs an instance of my combo box class, along with a list box.
2. Associates the list box with the combo box.
3. Provide access to the combo and list box properties that you need.

I have put together an example of how you might do this (see below). Simply put this in a file named "ListComboBox.cs". It works in much the same way as a regular list box, however it reacts more like a regular combo box. You will probably want to make some of your own alterations to this.

Thanks!
Lea Hayes

using System;
using System.ComponentModel;
using System.Drawing;
using System.Drawing.Design;
using System.Windows.Forms;

namespace CustomComboDemo
{
    public class ListComboBox : Control
    {
        #region Construction and destruction

        public ListComboBox()
        {
            List = new ListBox();
            
            Combo = new CustomComboBox.CustomComboBox(List);
            Combo.Dock = DockStyle.Fill;
            Controls.Add(Combo);

            List.SelectedIndexChanged += new EventHandler(List_SelectedIndexChanged);
            Combo.TextChanged += new EventHandler(Combo_TextChanged);
            Combo.KeyDown += new KeyEventHandler(ListComboBox_KeyDown);
        }

        #endregion

        #region Events

        void ListComboBox_KeyDown(object sender, KeyEventArgs e)
        {
            switch (e.KeyCode)
            {
                case Keys.Up:
                    if (List.SelectedIndex > 0)
                        --List.SelectedIndex;
                    break;
                case Keys.Down:
                    if (List.SelectedIndex + 1 < List.Items.Count)
                        ++List.SelectedIndex;
                    break;
                case Keys.Home:
                    List.SelectedIndex = List.Items.Count > 0 ? 0 : -1;
                    break;
                case Keys.End:
                    List.SelectedIndex = List.Items.Count - 1;
                    break;
            }
        }

        void List_SelectedIndexChanged(object sender, EventArgs e)
        {
            // Adjust content of combo box text.
            Combo.Text = (List.SelectedItem != null) ? List.SelectedItem.ToString() : "";
            Combo.HideDropDown();
            Combo.Select();
        }

        void Combo_TextChanged(object sender, EventArgs e)
        {
            // Adjust selection within list control.
            List.SelectedIndex = List.FindStringExact(Combo.Text);
        }

        #endregion

        #region Combo Methods

        public void ShowDropDown()
        {
            Combo.ShowDropDown();
        }

        public void HideDropDown()
        {
            Combo.HideDropDown();
        }

        #endregion

        #region Combo Properties

        [Browsable(false)]
        public bool IsDroppedDown
        {
            get { return Combo.IsDroppedDown; }
        }

        [Category("Custom Drop-Down"), Description("Indicates if drop-down is resizable.")]
        public bool AllowResizeDropDown
        {
            get { return Combo.AllowResizeDropDown; }
            set { Combo.AllowResizeDropDown = value; }
        }

        [Category("Custom Drop-Down"), Description("Indicates current sizing mode."), DefaultValue(CustomComboBox.CustomComboBox.SizeMode.UseComboSize)]
        public CustomComboBox.CustomComboBox.SizeMode DropDownSizeMode
        {
            get { return Combo.DropDownSizeMode; }
            set { Combo.DropDownSizeMode = value; }
        }

        [Category("Custom Drop-Down")]
        public Size DropSize
        {
            get { return Combo.DropSize; }
            set { Combo.DropSize = value; }
        }

        [Category("Custom Drop-Down"), Browsable(false)]
        public Size ControlSize
        {
            get { return Combo.ControlSize; }
            set { Combo.ControlSize = value; }
        }

        #endregion

        #region List Events

        public event EventHandler DataSourceChanged
        {
            add { List.DataSourceChanged += value; }
            remove { List.DataSourceChanged -= value; }
        }
        public event EventHandler DisplayMemberChanged
        {
            add { List.DisplayMemberChanged += value; }
            remove { List.DisplayMemberChanged -= value; }
        }
        public event ListControlConvertEventHandler Format
        {
            add { List.Format += value; }
            remove { List.Format -= value; }
        }

        [EditorBrowsable(EditorBrowsableState.Advanced)]
        [Browsable(false)]
        public event EventHandler FormatInfoChanged
        {
            add { List.FormatInfoChanged += value; }
            remove { List.FormatInfoChanged -= value; }
        }
        public event EventHandler FormatStringChanged
        {
            add { List.FormatStringChanged += value; }
            remove { List.FormatStringChanged -= value; }
        }
        public event EventHandler FormattingEnabledChanged
        {
            add { List.FormattingEnabledChanged += value; }
            remove { List.FormattingEnabledChanged -= value; }
        }
        public event EventHandler SelectedValueChanged
        {
            add { List.SelectedValueChanged += value; }
            remove { List.SelectedValueChanged -= value; }
        }
        public event EventHandler ValueMemberChanged
        {
            add { List.ValueMemberChanged += value; }
            remove { List.ValueMemberChanged -= value; }
        }

        #endregion

        #region List Methods

        public string GetItemText(object item)
        {
            return List.GetItemText(item);
        }

        public void ClearSelected()
        {
            List.ClearSelected();
        }

        public int FindString(string s)
        {
            return List.FindString(s);
        }

        public int FindString(string s, int startIndex)
        {
            return List.FindString(s, startIndex);
        }

        public int FindStringExact(string s)
        {
            return List.FindStringExact(s);
        }

        public int FindStringExact(string s, int startIndex)
        {
            return FindStringExact(s, startIndex);
        }

        public int GetItemHeight(int index)
        {
            return List.GetItemHeight(index);
        }

        #endregion

        #region List Properties

        [AttributeProvider(typeof(IListSource))]
        [DefaultValue("")]
        [RefreshProperties(RefreshProperties.Repaint)]
        public object DataSource
        {
            get { return List.DataSource; }
            set { List.DataSource = value; }
        }

        [TypeConverter("System.Windows.Forms.Design.DataMemberFieldConverter, System.Design, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a")]
        [DefaultValue("")]
        [Editor("System.Windows.Forms.Design.DataMemberFieldEditor, System.Design, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a", typeof(UITypeEditor))]
        public string DisplayMember
        {
            get { return List.DisplayMember; }
            set { List.DisplayMember = value; }
        }

        [EditorBrowsable(EditorBrowsableState.Advanced)]
        [Browsable(false)]
        [DefaultValue("")]
        public IFormatProvider FormatInfo
        {
            get { return List.FormatInfo; }
            set { List.FormatInfo = value; }
        }

        [MergableProperty(false)]
        [Editor("System.Windows.Forms.Design.FormatStringEditor, System.Design, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a", typeof(UITypeEditor))]
        [DefaultValue("")]
        public string FormatString
        {
            get { return List.FormatString; }
            set { List.FormatString = value; }
        }

        [DefaultValue(false)]
        public bool FormattingEnabled
        {
            get { return List.FormattingEnabled; }
            set { List.FormattingEnabled = value; }
        }

        public int SelectedIndex
        {
            get { return List.SelectedIndex; }
            set { List.SelectedIndex = value; }
        }

        [Browsable(false)]
        [DefaultValue("")]
        [Bindable(true)]
        [DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
        public object SelectedValue
        {
            get { return List.SelectedValue; }
            set { List.SelectedValue = value; }
        }

        [DefaultValue("")]
        [Editor("System.Windows.Forms.Design.DataMemberFieldEditor, System.Design, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a", typeof(UITypeEditor))]
        public string ValueMember
        {
            get { return List.ValueMember; }
            set { List.ValueMember = value; }
        }

        [RefreshProperties(RefreshProperties.Repaint)]
        [DefaultValue(true)]
        [Localizable(true)]
        public bool IntegralHeight
        {
            get { return List.IntegralHeight; }
            set { List.IntegralHeight = value; }
        }

        [Localizable(true)]
        [RefreshProperties(RefreshProperties.Repaint)]
        [DefaultValue(13)]
        public int ItemHeight
        {
            get { return List.ItemHeight; }
            set { List.ItemHeight = value; }
        }

        [Editor("System.Windows.Forms.Design.ListControlStringCollectionEditor, System.Design, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a", typeof(UITypeEditor))]
        [DesignerSerializationVisibility(DesignerSerializationVisibility.Content)]
        [Localizable(true)]
        [MergableProperty(false)]
        public ListBox.ObjectCollection Items
        {
            get { return List.Items; }
        }


        [DefaultValue(false)]
        public bool MultiColumn
        {
            get { return List.MultiColumn; }
            set { List.MultiColumn = value; }
        }

        [Localizable(true)]
        [DefaultValue(false)]
        public bool ScrollAlwaysVisible
        {
            get { return List.ScrollAlwaysVisible; }
            set { List.ScrollAlwaysVisible = value; }
        }

        [DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
        [Browsable(false)]
        public ListBox.SelectedIndexCollection SelectedIndices
        {
            get { return List.SelectedIndices; }
        }

        [Browsable(false)]
        [DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
        [Bindable(true)]
        public object SelectedItem
        {
            get { return List.SelectedItem; }
            set { List.SelectedItem = value; }
        }

        [DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
        [Browsable(false)]
        public ListBox.SelectedObjectCollection SelectedItems
        {
            get { return List.SelectedItems; }
        }

        public virtual SelectionMode SelectionMode
        {
            get { return List.SelectionMode; }
            set { List.SelectionMode = value; }
        }

        [DefaultValue(false)]
        public bool Sorted
        {
            get { return List.Sorted; }
            set { List.Sorted = value; }
        }

        [Browsable(false)]
        [DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
        public int TopIndex
        {
            get { return List.TopIndex; }
            set { List.TopIndex = value; }
        }

        [Browsable(false)]
        [DefaultValue(false)]
        public bool UseCustomTabOffsets
        {
            get { return List.UseCustomTabOffsets; }
            set { List.UseCustomTabOffsets = value; }
        }

        [DefaultValue(true)]
        public bool UseTabStops
        {
            get { return List.UseTabStops; }
            set { List.UseTabStops = value; }
        }

        #endregion

        #region Properties

        protected CustomComboBox.CustomComboBox Combo { get; private set; }
        protected ListBox List { get; private set; }

        #endregion
    }
}

Re: Using a ListBox?

metator10-Jul-09 4:24

metator

10-Jul-09 4:24

Hi again,

Sorry for my late reply. I really like to thank for your help. I find this solution very elegant. You implemented through composition and my mistake was trying to do it through inheritance. This avoids having to unhide those unwanted properties. One minor suggestion: i was getting AccessViolationException when tring to set DropSize property (in designer generated code). I corrected this by changing the ListComboBox's parent class from Control to UserControl.

Best regards.

You realize that everything you learn is in fact just learned, not necessarily true...

Re: Using a ListBox?

Lea Hayes10-Jul-09 14:55

Lea Hayes

10-Jul-09 14:55

Hi,

No problem, I am glad that I was able to help you.

I will take a look into the AccessViolationException that you speak of.

Many thanks,
Lea Hayes

How do I add this to my project pls?

Member 197457016-Apr-09 3:15

Member 1974570

16-Apr-09 3:15

Hi I am relatively new to this VS2005 and .Net winform development. Would you advice on how to add this control to my project for testing and possible customization please?!

TIA

Re: How do I add this to my project pls?

Lea Hayes26-Apr-09 15:41

Lea Hayes

26-Apr-09 15:41

Hi,

Thanks for your interest!

To add this control to your project:

1. Select "Download source (Version 2.1) - 8.02 KB" from the top of this page.
2. Copy the files into your project directory.
3. Add all of these files into your C# project.
4. Rebuild your project from the "Build" menu.
5. Run your project, and then exit it. In some cases this eases the following step.
6. Drag and drop the control from the control box panel into your form.
7. You can then interact with your control by following the information in this article.

Many thanks,
Lea Hayes

Re: How do I add this to my project pls?

Member 197457028-Apr-09 17:25

Member 1974570

28-Apr-09 17:25

Hi
I have done that but I get the following error

1. I tried to build the project again, then my vs2005 say there is missing directive or assembly reference in both "OldNewEvent.cs" and the "CustomComboBox.cs" files,

Here is what I found

- I open the source of CustomComboBox.cs then I found a type/namespace "ParentControlDesigner" is underlined (saying not found)

- then I open the source of OldNewEvent.cs and found a line "System.Linq" in the Declaration section is underlined (saying does not exists)

I am using .net 2.0 with vs2005 only.

Do I missed anything?

TIA

Re: How do I add this to my project pls?

Lea Hayes29-Apr-09 12:26

Lea Hayes

29-Apr-09 12:26

Hi TIA,

> I open the source of CustomComboBox.cs then I found a type/namespace "ParentControlDesigner" is underlined (saying not found)

To solve this problem add the "System.Design" reference into your project.

> then I open the source of OldNewEvent.cs and found a line "System.Linq" in the Declaration section is underlined (saying does not exists)

In the "OldNewEvent.cs" file simply remove all of the using statements apart from "using System;" so that you have something which looks like the following. I think that I may have been using a later version of .NET when I made changes to the source files. "System.Linq" is not actually being used in this source, so it can just be removed.

using System;

namespace CustomComboBox
{
    public class OldNewEventArgs<T> : EventArgs
    {
        public OldNewEventArgs(T oldValue, T newValue)
        {
            OldValue = oldValue;
            NewValue = newValue;
        }

        public T OldValue
        {
            get { return this.m_oldValue; }
            protected set { this.m_oldValue = value; }
        }
        public T NewValue
        {
            get { return this.m_newValue; }
            protected set { this.m_newValue = value; }
        }

        T m_oldValue = default(T);
        T m_newValue = default(T);
    }

    public delegate void OldNewEventHandler<T>(object sender, OldNewEventArgs<T> e);
}

Give that a go and let me know how you get on.

Thanks,
Lea Hayes

Setting the datasource of the combo box

CraigKniese5-Dec-08 8:53

CraigKniese

5-Dec-08 8:53

I'm trying to set the datasource of the datagridview of combobox1 to a datatable, but it's not working. If I just add a datagridview to the form it works. But it doesn't work with the gridview in the combo box. Why is this?

Re: Setting the datasource of the combo box

Lea Hayes9-Dec-08 1:28

Lea Hayes

9-Dec-08 1:28

Hi,

Yes this is an odd problem that you have discovered. However, I have two simple workarounds that you could use:

Workaround #1
Use the following code:

// Create grid view control.
DataGridView gridView = new DataGridView();
gridView.BorderStyle = BorderStyle.None;
gridView.AutoGenerateColumns = true;
gridView.ColumnHeadersHeightSizeMode = System.Windows.Forms.DataGridViewColumnHeadersHeightSizeMode.AutoSize;
gridView.DataSource = this.peopleBindingSource1;
gridView.Visible = false;
// The following line is very important, the control is temporarily added to the form.
Controls.Add(gridView);
            
this.customComboBox1.DropDownControl = gridView;

Workaround #2
Add your data grid view to your form in the form designer, then simply reference it in the code:

this.customComboBox1.DropDownControl = this.dataGridView1;

Please let me know if this helps!

Re: Setting the datasource of the combo box

Coarval COOP V25-Sep-14 1:00

Coarval COOP V

25-Sep-14 1:00

I found the problem and the solution.
The problem is that the DropDownControl doesn't have a BindingContext.

This is the code that solved the problem in my project.

protected override void OnBindingContextChanged(EventArgs e)
{
    base.OnBindingContextChanged(e);
    if (this.DropDownControl != null)
    {
        this.DropDownControl.BindingContext = this.BindingContext;
    }
}

This overrides the OnBindingContextChanged event of the CustomCombobox class to assign it automatically to the DropDownControl.

Re: Setting the datasource of the combo box

Dyolf_Knip13-Jan-22 6:21

Dyolf_Knip

13-Jan-22 6:21

Sweet jesus, thank you for this. This control was perfect for everything I needed except for the fact that I couldn't freaking bind it to anything.

Blush | :O

Nice - Suggestions

jmcstone3-Dec-08 1:55

jmcstone

3-Dec-08 1:55

Thanks for the very nice work. Here are some changes that I made that you may want to consider.

1) I wanted to be able to hide the dropdown when the dropdowncontrol was hidden so in the PopupControl class in the InitializeHost method I hooked up to the controls.VisibleChanged method and when the control became non visible I called the Hide method on PopupControl.

2) The CustomComboBox class remembers the initial control size. This caused issues as I modified the size of the control (i.e. added items to my datagridview) after the control was initially visible. Then upon subsequent dropdowns the the dropdown was sized improperly. I added logic to always use the actual control size from within the AutoSizeDropDown.

Thanks again.

Re: Nice - Suggestions

Lea Hayes9-Dec-08 1:02

Lea Hayes

9-Dec-08 1:02

Hi,

Thank you for your kind words, and your two suggestions.

The second point that you mention was a design requirement for the project that I was working on at that point in time. However, I suspect that I could add a property to the control which allows the programmer to decide whether they want that functionality or not.

Thanks again!
Lea Hayes

Escape issue

Brad Bruce16-Jul-08 0:33

Brad Bruce

16-Jul-08 0:33

It's easier to just list the steps...

1. Click the down arrow of any of the controls in the demo
2. Enter some data on the dropped control
3. Press escape
(The entered value doesn't show up -- Good)
4. Click the down arrow again
5. The previously entered data is still there (Not good. Most users expect the drop down and the displayed information to match)

I've been working on a similar issue at work, so that was the first thing I tested. The control looks GREAT! I'll probably base several of my existing controls on it. (Less support for me! Smile | :)

)

Re: Escape issue

Lea Hayes17-Jul-08 7:32

Lea Hayes

17-Jul-08 7:32

Hi,

I have checked what you are saying, but for me this was the intended functionality. If a value change is accepted within the drop-down then it is possible to reflect changes within the combo-box text area. Alternatively application specific code can be added to interact directly with the drop-down control.

If you wanted to adjust this functionality there are two ways that spring to mind:

1. Destroy and reconstruct the drop-down each time it is displayed (for some applications this may be too inefficient).

2. Add an interface which drop-down controls can optionally implement. If this interface is implemented then the drop-down control could have an oppertunity to reset itself upon drop-down (or other events).

public interface IDropDownControl
{
   void ResetBeforeDropDown();
}

// This one DOES implement the drop-down control interface and so
// will be reset to whatever state upon drop-down.
public class MyControlA : UserControl, IDropDownControl
{
   public ResetBeforeDropDown()
   {
      listBox1.SelectedIndex = -1;
   }
}

// This one does NOT implement the drop-down control, but is STILL
// compatible.
public class MyControlB : UserControl
{
}

Then implement a class along the lines of:

public class MyCustomComboBox : CustomComboBox
{
   protected override void ShowDropDown()
   {
      // If drop down control interface is implemented, invoke the
      // associated methods.
      IDropDownControl dropDownCtrl = DropDownControl as IDropDownControl;
      if (dropDownCtrl != null)
          dropDownCtrl.ResetBeforeDropDown();

      // Show drop down like before.
      base.ShowDropDown();
   }
}

I hope that this is of help!

Lea Hayes

Please !! help custom

kristianbr14-Jul-08 7:10

kristianbr

14-Jul-08 7:10

Hello I am a beginner in C # and would like a hint of how to customize the object appears in the dropdown window also a window into modal.

Tranks

Cristiano / Brazil

Re: Please !! help custom

Lea Hayes14-Jul-08 9:37

Lea Hayes

14-Jul-08 9:37

Hi Cristiano!

When you say how to customize the object that appears in the dropdown window, are you referring to how to assign a drop-down control, or rather how to interact with a control which has already been assigned?

Please can you explain what you mean by display a window into modal? Do you want a dialog box to appear modally when you click the drop-down arrow instead of the dropdown? Or are you attempting to have a modal window appear when (for example) a button is pressed inside a dropdown control?

Thanks for taking interest in my control! I hope that it is of some use to you! Big Grin | :-D

Lea Hayes

Re: Please !! help custom

kristianbr20-Jul-08 8:07

kristianbr

20-Jul-08 8:07

Accurately this! the two ways that Sir understood…. both in form modal, with the content of dropdrow! to make research based in 1 textbox above of one grid or another control as desired or usercontrol.

Tks for the aid and excuse for the delay

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