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ListBox.MeasureItem Event

Occurs when an owner-drawn ListBox is created and the sizes of the list items are determined.

Namespace: System.Windows.Forms
Assembly: System.Windows.Forms (in system.windows.forms.dll)

public event MeasureItemEventHandler MeasureItem
/** @event */
public void add_MeasureItem (MeasureItemEventHandler value)

/** @event */
public void remove_MeasureItem (MeasureItemEventHandler value)

JScript supports the use of events, but not the declaration of new ones.

You can create an event handler for this event to specify the size an item will be made before it is drawn in the DrawItem event. The event is only raised when the DrawMode property is set to OwnerDrawVariable.

The maximum valid height of a ListBox item is 255 pixels. Setting the ItemHeight property of the MeasureItemEventArgs to a value greater than 255 when handling this event may yield unexpected results.

For more information about handling events, see Consuming Events.

The following code example demonstrates an owner-drawn ListBox by setting the DrawMode property to OwnerDrawVariable and handling the DrawItem and MeasureItem events. It also demonstrates setting the BorderStyle and ScrollAlwaysVisible properties and using the AddRange method.

To run this example, paste it in an empty form that imports the System.Drawing namespace and the System.Windows.Forms namespace. Call InitializeOwnerDrawnListBox from the form's constructor or Load event-handling method.

internal System.Windows.Forms.ListBox ListBox1;

private void InitializeOwnerDrawnListBox()
{
    this.ListBox1 = new System.Windows.Forms.ListBox();

    // Set the location and size.
    ListBox1.Location = new Point(20, 20);
    ListBox1.Size = new Size(240, 240);

    // Populate the ListBox.ObjectCollection property 
    // with several strings, using the AddRange method.
    this.ListBox1.Items.AddRange(new object[]{"System.Windows.Forms", 
        "System.Drawing", "System.Xml", "System.Net", "System.Runtime.Remoting", 
        "System.Web"});

    // Turn off the scrollbar.
    ListBox1.ScrollAlwaysVisible = false;

    // Set the border style to a single, flat border.
    ListBox1.BorderStyle = BorderStyle.FixedSingle;

    // Set the DrawMode property to the OwnerDrawVariable value. 
    // This means the MeasureItem and DrawItem events must be 
    // handled.
    ListBox1.DrawMode = DrawMode.OwnerDrawVariable;
    ListBox1.MeasureItem += 
        new MeasureItemEventHandler(ListBox1_MeasureItem);
    ListBox1.DrawItem += new DrawItemEventHandler(ListBox1_DrawItem);
    this.Controls.Add(this.ListBox1);
    
}


// Handle the DrawItem event for an owner-drawn ListBox.
private void ListBox1_DrawItem(object sender, DrawItemEventArgs e)
{

    // If the item is the selected item, then draw the rectangle
    // filled in blue. The item is selected when a bitwise And  
    // of the State property and the DrawItemState.Selected 
    // property is true.
    if ((e.State & DrawItemState.Selected) == DrawItemState.Selected)
    {
        e.Graphics.FillRectangle(Brushes.CornflowerBlue, e.Bounds);
    }
    else
    {
        // Otherwise, draw the rectangle filled in beige.
        e.Graphics.FillRectangle(Brushes.Beige, e.Bounds);
    }

    // Draw a rectangle in blue around each item.
    e.Graphics.DrawRectangle(Pens.Blue, e.Bounds);

    // Draw the text in the item.
    e.Graphics.DrawString(ListBox1.Items[e.Index].ToString(),
        this.Font, Brushes.Black, e.Bounds.X, e.Bounds.Y);

    // Draw the focus rectangle around the selected item.
    e.DrawFocusRectangle();
}

// Handle the MeasureItem event for an owner-drawn ListBox.
private void ListBox1_MeasureItem(object sender, 
    MeasureItemEventArgs e)
{

    // Cast the sender object back to ListBox type.
    ListBox theListBox = (ListBox) sender;

    // Get the string contained in each item.
    string itemString = (string) theListBox.Items[e.Index];

    // Split the string at the " . "  character.
    string[] resultStrings = itemString.Split('.');

    // If the string contains more than one period, increase the 
    // height by ten pixels; otherwise, increase the height by 
    // five pixels.
    if (resultStrings.Length>2)
    {
        e.ItemHeight += 10;
    }
    else
    {
        e.ItemHeight += 5;
    }

}


private System.Windows.Forms.ListBox listBox1;

private void InitializeOwnerDrawnListBox()
{
    this.listBox1 = new System.Windows.Forms.ListBox();
    // Set the location and size.
    listBox1.set_Location(new Point(20, 20));
    listBox1.set_Size(new Size(240, 240));
    // Populate the ListBox.ObjectCollection property 
    // with several strings, using the AddRange method.
    this.listBox1.get_Items().AddRange(new Object[] { 
        "System.Windows.Forms", "System.Drawing", 
        "System.Xml", "System.Net", "System.Runtime.Remoting", 
        "System.Web" });
    // Turn off the scrollbar.
    listBox1.set_ScrollAlwaysVisible(false);
    // Set the border style to a single, flat border.
    listBox1.set_BorderStyle(BorderStyle.FixedSingle);
    // Set the DrawMode property to the OwnerDrawVariable value. 
    // This means the MeasureItem and DrawItem events must be 
    // handled.
    listBox1.set_DrawMode(DrawMode.OwnerDrawVariable);
    listBox1.add_MeasureItem(new MeasureItemEventHandler(
        listBox1_MeasureItem));
    listBox1.add_DrawItem(new DrawItemEventHandler(listBox1_DrawItem));
    this.get_Controls().Add(this.listBox1);
} //InitializeOwnerDrawnListBox

// Handle the DrawItem event for an owner-drawn ListBox.
private void listBox1_DrawItem(Object sender, DrawItemEventArgs e)
{
    // If the item is the selected item, then draw the rectangle
    // filled in blue. The item is selected when a bitwise And  
    // of the State property and the DrawItemState.Selected 
    // property is true.
    if ((e.get_State() & DrawItemState.Selected) 
        == DrawItemState.Selected) {
        e.get_Graphics().FillRectangle(Brushes.get_CornflowerBlue(), 
            e.get_Bounds());
    }
    else {
        // Otherwise, draw the rectangle filled in beige.
        e.get_Graphics().FillRectangle(Brushes.get_Beige(), 
            e.get_Bounds());
    }
    // Draw a rectangle in blue around each item.
    e.get_Graphics().DrawRectangle(Pens.get_Blue(), e.get_Bounds());
    // Draw the text in the item.
    e.get_Graphics().DrawString(listBox1.get_Items().get_Item(
        e.get_Index()).ToString(), this.get_Font(), 
        Brushes.get_Black(), e.get_Bounds().get_X(), 
        e.get_Bounds().get_Y());
    // Draw the focus rectangle around the selected item.
    e.DrawFocusRectangle();
} //listBox1_DrawItem

// Handle the MeasureItem event for an owner-drawn ListBox.
private void listBox1_MeasureItem(Object sender, MeasureItemEventArgs e)
{
    // Cast the sender object back to ListBox type.
    ListBox theListBox = (ListBox) sender;
    // Get the string contained in each item.
    String itemString = (String)(theListBox.get_Items().
           get_Item(e.get_Index()));
    // Split the string at the " . "  character.
    String resultStrings[] = itemString.Split(new char[] { '.' });
    // If the string contains more than one period, increase the 
    // height by ten pixels; otherwise, increase the height by 
    // five pixels.
    if (resultStrings.length > 2) {
        e.set_ItemHeight(e.get_ItemHeight() + 10);
    }
    else {
        e.set_ItemHeight(e.get_ItemHeight() + 5);
    }
} //listBox1_MeasureItem

Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

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

.NET Framework

Supported in: 2.0, 1.1, 1.0

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