Export (0) Print
Expand All

ComboBox.MeasureItem Event

Occurs each time an owner-drawn ComboBox item needs to be drawn and when the sizes of the list items are determined.

[Visual Basic]
Public Event MeasureItem As MeasureItemEventHandler
[C#]
public event MeasureItemEventHandler MeasureItem;
[C++]
public: __event MeasureItemEventHandler* MeasureItem;

[JScript] In JScript, you can handle the events defined by a class, but you cannot define your own.

Event Data

The event handler receives an argument of type MeasureItemEventArgs containing data related to this event. The following MeasureItemEventArgs properties provide information specific to this event.

Property Description
Graphics Gets the Graphics object to measure against.
Index Gets or sets the index of the item for which the height and width is needed.
ItemHeight Gets or sets the height of the item specified by the Index.
ItemWidth Gets or sets the width of the item specified by the Index.

Remarks

You can create an event handler for this event to specify the size an item is made before it is drawn in the DrawItem event.

For more information about handling events, see Consuming Events.

Example

[Visual Basic, C#] 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.

[Visual Basic] 

    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


[C#] 

    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();
    }

[C++, JScript] No example is available for C++ or JScript. To view a Visual Basic or C# example, click the Language Filter button Language Filter in the upper-left corner of the page.

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

Show:
© 2014 Microsoft