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ComboBox.DrawMode Property

Gets or sets a value indicating whether your code or the operating system will handle drawing of elements in the list.

[Visual Basic]
Public Property DrawMode As DrawMode
[C#]
public DrawMode DrawMode {get; set;}
[C++]
public: __property DrawMode get_DrawMode();
public: __property void set_DrawMode(DrawMode);
[JScript]
public function get DrawMode() : DrawMode;
public function set DrawMode(DrawMode);

Property Value

One of the DrawMode enumeration values. The default is DrawMode.Normal.

Exceptions

Exception Type Condition
InvalidEnumArgumentException The value is not a valid DrawMode enumeration value.

Example

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 method.

[SampleID='System.Windows.Forms.ComboBoxOwnerDrawn' SnippetID='1']
--------- Languages displayed= cs, vb ---------
--------- cs ---------
--------- Snippet 1 ---------
    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.
    protected 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();
    }
--------- vb ---------
--------- Snippet 1 ---------
    Friend WithEvents ComboBox1 As System.Windows.Forms.ComboBox
    Private animals() As String
  
    ' 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 Sub InitializeComboBox()
        Me.ComboBox1 = New ComboBox
        Me.ComboBox1.DrawMode = System.Windows.Forms.DrawMode.OwnerDrawVariable
        Me.ComboBox1.Location = New System.Drawing.Point(10, 20)
        Me.ComboBox1.Name = "ComboBox1"
        Me.ComboBox1.Size = New System.Drawing.Size(100, 120)
        Me.ComboBox1.DropDownWidth = 250
        Me.ComboBox1.TabIndex = 0
        Me.ComboBox1.DropDownStyle = ComboBoxStyle.DropDown
        animals = New String() {"Elephant", "c r o c o d i l e", "lion"}
        ComboBox1.DataSource = animals
        Me.Controls.Add(Me.ComboBox1)
    End Sub
    ' 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 Sub ComboBox1_MeasureItem(ByVal sender As Object, _
        ByVal e As System.Windows.Forms.MeasureItemEventArgs) _
            Handles ComboBox1.MeasureItem
        Select Case e.Index
            Case 0
                e.ItemHeight = 45
            Case 1
                e.ItemHeight = 20
            Case 2
                e.ItemHeight = 35
        End Select
        e.ItemWidth = 260
    End Sub
    ' 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.
    Protected Sub ComboBox1_DrawItem(ByVal sender As Object,  _ 
        ByVal e As System.Windows.Forms.DrawItemEventArgs) _
        Handles ComboBox1.DrawItem
        Dim size As Single
        Dim myFont As System.Drawing.Font
        Dim family As FontFamily
        Dim animalColor As New System.Drawing.Color
        Select Case e.Index
            Case 0
                size = 30
                animalColor = System.Drawing.Color.Gray
                family = FontFamily.GenericSansSerif
            Case 1
                size = 10
                animalColor = System.Drawing.Color.LawnGreen
                family = FontFamily.GenericMonospace
            Case 2
                size = 15
                animalColor = System.Drawing.Color.Tan
                family = FontFamily.GenericSansSerif
        End Select
        ' 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.
        Dim rectangle As 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()
      End Sub

Requirements

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family

See Also

ComboBox Class | ComboBox Members | System.Windows.Forms Namespace | DrawMode | DrawItem | MeasureItem

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