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ComboBox.DropDownWidth Property

Gets or sets the width of the of the drop-down portion of a combo box.

Namespace:  System.Windows.Forms
Assembly:  System.Windows.Forms (in System.Windows.Forms.dll)

public int DropDownWidth { get; set; }

Property Value

Type: System.Int32
The width, in pixels, of the drop-down box.

ExceptionCondition
ArgumentException

The specified value is less than one.

If a value has not been set for the DropDownWidth, this property returns the Width of the combo box.

NoteNote

The width of the drop-down cannot be smaller than the ComboBox width.

The following code example demonstrates how to create an owner-drawn combo box by setting the DrawMode property to OwnerDrawnVariable and handling the DrawItem and MeasureItem events. It also demonstrates setting the DropDownWidth and DropDownStyle properties. To run the example, paste the following code in a form. Call the InitializeComboBox method in the form's constructor or Load event.


	internal System.Windows.Forms.ComboBox ComboBox1;
	private string[] animals;

	// This method initializes the owner-drawn combo box. 
	// The drop-down width is set much wider than the size of the combo box 
	// to accomodate the large items in the list.  The drop-down style is set to  
	// ComboBox.DropDown, which requires the user to click on the arrow to  
	// see the list. 
	private void InitializeComboBox()
	{
		this.ComboBox1 = new ComboBox();
		this.ComboBox1.DrawMode = 
			System.Windows.Forms.DrawMode.OwnerDrawVariable;
		this.ComboBox1.Location = new System.Drawing.Point(10, 20);
		this.ComboBox1.Name = "ComboBox1";
		this.ComboBox1.Size = new System.Drawing.Size(100, 120);
		this.ComboBox1.DropDownWidth = 250;
		this.ComboBox1.TabIndex = 0;
		this.ComboBox1.DropDownStyle = ComboBoxStyle.DropDown;
		animals = new string[]{"Elephant", "c r o c o d i l e", "lion"};
		ComboBox1.DataSource = animals;
		this.Controls.Add(this.ComboBox1);

		// Hook up the MeasureItem and DrawItem events 
		this.ComboBox1.DrawItem += 
			new DrawItemEventHandler(ComboBox1_DrawItem);
		this.ComboBox1.MeasureItem += 
			new MeasureItemEventHandler(ComboBox1_MeasureItem);
	}

	// If you set the Draw property to DrawMode.OwnerDrawVariable,  
	// you must handle the MeasureItem event. This event handler  
	// will set the height and width of each item before it is drawn.  
	private void ComboBox1_MeasureItem(object sender, 
		System.Windows.Forms.MeasureItemEventArgs e)
	{

		switch(e.Index)
		{
			case 0:
				e.ItemHeight = 45;
				break;
			case 1:
				e.ItemHeight = 20;
				break;
			case 2:
				e.ItemHeight = 35;
				break;
		}
		e.ItemWidth = 260;

	}

	// You must handle the DrawItem event for owner-drawn combo boxes.   
	// This event handler changes the color, size and font of an  
	// item based on its position in the array. 
	private void ComboBox1_DrawItem(object sender, 
		System.Windows.Forms.DrawItemEventArgs e)
	{

		float size = 0;
		System.Drawing.Font myFont;
		FontFamily family = null;

		System.Drawing.Color animalColor = new System.Drawing.Color();
		switch(e.Index)
		{
			case 0:
				size = 30;
				animalColor = System.Drawing.Color.Gray;
				family = FontFamily.GenericSansSerif;
				break;
			case 1:
				size = 10;
				animalColor = System.Drawing.Color.LawnGreen;
				family = FontFamily.GenericMonospace;
				break;
			case 2:
				size = 15;
				animalColor = System.Drawing.Color.Tan;
				family = FontFamily.GenericSansSerif;
				break;
		}

		// Draw the background of the item.
		e.DrawBackground();

		// Create a square filled with the animals color. Vary the size 
		// of the rectangle based on the length of the animals name.
		Rectangle rectangle = new Rectangle(2, e.Bounds.Top+2, 
				e.Bounds.Height, e.Bounds.Height-4);
		e.Graphics.FillRectangle(new SolidBrush(animalColor), rectangle);

		// Draw each string in the array, using a different size, color, 
		// and font for each item.
		myFont = new Font(family, size, FontStyle.Bold);
		e.Graphics.DrawString(animals[e.Index], myFont, System.Drawing.Brushes.Black, new RectangleF(e.Bounds.X+rectangle.Width, e.Bounds.Y, e.Bounds.Width, e.Bounds.Height));

		// Draw the focus rectangle if the mouse hovers over an item.
		e.DrawFocusRectangle();
	}

.NET Framework

Supported in: 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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