Re: Create control with drop-down similar to ComboBox

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It's an article that needs doing for WFT&T but it's fairly involved and not
something I can bash out in a few minutes.

--
Bob Powell [MVP]
Visual C#, System.Drawing

Ramuseco Limited .NET consulting
http://www.ramuseco.com

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"Bob Dankert" <bobatnvsn-itdotcom@xxxxxxxxxxxxx> wrote in message
news:OoMR0BPeGHA.1436@xxxxxxxxxxxxxxxxxxxxxxx
Thanks for the response Bob and Linda,

Linda, unfortunately I can not use the combobox to do as I want as I need
to change what is drawn in the combobox dropdown based on the position of
the mouse and numerous other things (buttons, etc) and need to have events
such as mouseover, mousedown, and click - all of which are not registered
by the combobox in the dropdown portion. I agree with Bob that using a
form to display the drop-down portion is very clumsy and not a very good
solution at all (unless someone can provide me an example of a "good"
implementation, but I do not think this is possible).

Does anyone by any chance have an example of using the NativeWindow
implementation that Bob Powell described?

Thanks,

Bob Dankert

"Bob Powell [MVP]" <bob@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:%23YSd4jMeGHA.4892@xxxxxxxxxxxxxxxxxxxxxxx
Hi Linda,
This solution is a poor one because the form would take the focus and
inactivate the main window form. The functionality of the dropdown would
be difficult to manage too.

The correct way to do this is to derive a class from NativeWindow and
create a popup window, similar to a tooltip window, that can be shown
using the SW_SHOWNOACTIVATE setting and the ShowWindow function via
interop. A class created in this way would mimic the behaviour of the
base Win32 controls and it would be easier to create the desired internal
functionality such as item selection and so-on.

As proof of it's nastiness I created a quick and dirty combo-box in the
code below my signature. It's horrible in every way.

--
Bob Powell [MVP]
Visual C#, System.Drawing

Ramuseco Limited .NET consulting
http://www.ramuseco.com

Find great Windows Forms articles in Windows Forms Tips and Tricks
http://www.bobpowell.net/tipstricks.htm

Answer those GDI+ questions with the GDI+ FAQ
http://www.bobpowell.net/faqmain.htm

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--------------------------------------------------------------------------
public class FauxCombo : System.Windows.Forms.UserControl

{

private System.Windows.Forms.TextBox textBox1;

private System.Windows.Forms.Button button1;

/// <summary>

/// Required designer variable.

/// </summary>

private System.ComponentModel.Container components = null;

public FauxCombo()

{

// This call is required by the Windows.Forms Form Designer.

InitializeComponent();

// TODO: Add any initialization after the InitializeComponent call

}

/// <summary>

/// Clean up any resources being used.

/// </summary>

protected override void Dispose( bool disposing )

{

if( disposing )

{

if(components != null)

{

components.Dispose();

}

}

base.Dispose( disposing );

}

#region Component Designer generated code

/// <summary>

/// Required method for Designer support - do not modify

/// the contents of this method with the code editor.

/// </summary>

private void InitializeComponent()

{

this.textBox1 = new System.Windows.Forms.TextBox();

this.button1 = new System.Windows.Forms.Button();

this.SuspendLayout();

//

// textBox1

//

this.textBox1.Location = new System.Drawing.Point(0, 0);

this.textBox1.Name = "textBox1";

this.textBox1.TabIndex = 0;

this.textBox1.Text = "textBox1";

//

// button1

//

this.button1.Location = new System.Drawing.Point(104, 0);

this.button1.Name = "button1";

this.button1.Size = new System.Drawing.Size(23, 23);

this.button1.TabIndex = 1;

this.button1.Text = "V";

this.button1.Click += new System.EventHandler(this.button1_Click);

//

// FauxCombo

//

this.Controls.Add(this.button1);

this.Controls.Add(this.textBox1);

this.Name = "FauxCombo";

this.Size = new System.Drawing.Size(128, 24);

this.ResumeLayout(false);

}

#endregion

Form dropdown;

private void button1_Click(object sender, System.EventArgs e)

{

if(dropdown==null)

{

dropdown=new Form();

dropdown.FormBorderStyle=FormBorderStyle.None;

dropdown.BackColor=Color.White;

dropdown.ShowInTaskbar=false;

dropdown.StartPosition=FormStartPosition.Manual;

dropdown.Location=this.PointToScreen(new Point(0,23));

dropdown.Size=new Size(80,200);

dropdown.MouseDown+=new MouseEventHandler(dropdown_MouseDown);

dropdown.Closed+=new EventHandler(dropdown_Closed);

dropdown.Show();

dropdown.Capture=true;

}

else

{

dropdown.Hide();

dropdown.MouseDown-=new MouseEventHandler(dropdown_MouseDown);

dropdown.Closed-=new EventHandler(dropdown_Closed);

dropdown.Dispose();

dropdown=null;

}

}

private void dropdown_MouseDown(object sender, MouseEventArgs e)

{

Form f=(Form)sender;

if(!f.ClientRectangle.Contains(new Point(e.X,e.Y)))

f.Close();

}

private void dropdown_Closed(object sender, EventArgs e)

{

dropdown.MouseDown-=new MouseEventHandler(dropdown_MouseDown);

dropdown.Closed-=new EventHandler(dropdown_Closed);

dropdown.Dispose();

dropdown=null;

}

}



"Linda Liu [MSFT]" <v-lliu@xxxxxxxxxxxxxxxxxxxx> wrote in message
news:jd8LqYJeGHA.188@xxxxxxxxxxxxxxxxxxxxxxxx
Hi Bob,

Thank you for posting.
I have two questions on your issue.
1. Since your custom control imitates the behavior of the drop-down
component of a ComboBox, why don't you use the ComboBox directly?

2. What are you going to paint in the lower drop-down area of your
custom
control?

To make the drop-down portion "float", I think you may have a try
replacing
the lower drop-down area of your custom control with a winform whose
FormBorderStyle property is set to None. When you want to display the
drop-down portion, you may show the form in a location you would like.

I am looking forward to your reply. Thanks.


Sincerely,
Linda Liu
Microsoft Online Community Support

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