MeasureItemEventHandler Delegate


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Represents the method that will handle the MeasureItem event of the ListBox, ComboBox, CheckedListBox, or MenuItem controls.

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

Public Delegate Sub MeasureItemEventHandler (
	sender As Object,
	e As MeasureItemEventArgs


Type: System.Object

The source of the event.

Type: System.Windows.Forms.MeasureItemEventArgs

A MeasureItemEventArgs that contains the event data.

When you create a MeasureItemEventHandler delegate, you identify the method that will handle the event. To associate the event with your event handler, add an instance of the delegate to the event. The event handler is called whenever the event occurs, unless you remove the delegate. For more information about event handler delegates, see Handling and Raising Events.

The following code example demonstrates using the Graphics property to perform custom drawing of the items in a ListBox.

Public Class Form1
   Inherits System.Windows.Forms.Form
   Private WithEvents listBox1 As System.Windows.Forms.ListBox
   Private components As System.ComponentModel.Container = Nothing

   Private FontSize As Single = 12.0F

   '  This sample displays a ListBox that contains a list of all the fonts
   '  installed on the system and draws each item in its respective font.
   Public Sub New()

      ' Populate control with the fonts installed on the system.
      Dim families As FontFamily() = FontFamily.Families

      Dim family As FontFamily
      For Each family In families
         Dim style As FontStyle = FontStyle.Regular

         ' Monotype Corsiva is only available in italic
         If family.Name = "Monotype Corsiva" Then
            style = style Or FontStyle.Italic
         End If

         listBox1.Items.Add(New ListBoxFontItem(New Font(family.Name, FontSize, style, GraphicsUnit.Point)))
      Next family
   End Sub

   Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
      If disposing Then
         If (components IsNot Nothing) Then
         End If

         If (foreColorBrush IsNot Nothing) Then
         End If
      End If

   End Sub

   Private Sub InitializeComponent()
      Me.listBox1 = New System.Windows.Forms.ListBox()
      ' listBox1
      Me.listBox1.DrawMode = System.Windows.Forms.DrawMode.OwnerDrawVariable
      Me.listBox1.Location = New System.Drawing.Point(16, 48)
      Me.listBox1.Name = "listBox1"
      Me.listBox1.SelectionMode = System.Windows.Forms.SelectionMode.MultiExtended
      Me.listBox1.Size = New System.Drawing.Size(256, 134)
      Me.listBox1.TabIndex = 0
      ' Form1
      Me.ClientSize = New System.Drawing.Size(292, 273)
      Me.Controls.AddRange(New System.Windows.Forms.Control() {Me.listBox1})
      Me.Name = "Form1"
      Me.Text = "Form1"
   End Sub

   <STAThread()> Shared Sub Main()
      Application.Run(New Form1())
   End Sub

   Private Sub listBox1_MeasureItem(ByVal sender As Object, ByVal e As System.Windows.Forms.MeasureItemEventArgs) Handles listBox1.MeasureItem
      Dim font As Font = CType(listBox1.Items(e.Index), ListBoxFontItem).Font
      Dim stringSize As SizeF = e.Graphics.MeasureString(font.Name, font)

      ' Set the height and width of the item
      e.ItemHeight = CInt(stringSize.Height)
      e.ItemWidth = CInt(stringSize.Width)
   End Sub

   ' For efficiency, cache the brush used for drawing.
   Private foreColorBrush As SolidBrush

   Private Sub listBox1_DrawItem(ByVal sender As Object, ByVal e As System.Windows.Forms.DrawItemEventArgs) Handles listBox1.DrawItem
      Dim brush As Brush

      ' Create the brush using the ForeColor specified by the DrawItemEventArgs
      If foreColorBrush Is Nothing Then
         foreColorBrush = New SolidBrush(e.ForeColor)
         If Not foreColorBrush.Color.Equals(e.ForeColor) Then
            ' The control's ForeColor has changed, so dispose of the cached brush and
            ' create a new one.
            foreColorBrush = New SolidBrush(e.ForeColor)
         End If
      End If

      ' Select the appropriate brush depending on if the item is selected.
      ' Since State can be a combinateion (bit-flag) of enum values, you can't use
      ' "==" to compare them.
      If (e.State And DrawItemState.Selected) = DrawItemState.Selected Then
         brush = SystemBrushes.HighlightText
         brush = foreColorBrush
      End If

      ' Perform the painting.
      Dim font As Font = CType(listBox1.Items(e.Index), ListBoxFontItem).Font
      e.Graphics.DrawString(font.Name, font, brush, e.Bounds.X, e.Bounds.Y)
   End Sub

   '  A wrapper class for use with storing Fonts in a ListBox.  Since ListBox uses the
   '  ToString() of its items for the text it displays, this class is needed to return
   '  the name of the font, rather than its ToString() value.
   Public Class ListBoxFontItem
      Public Font As Font

      Public Sub New(ByVal f As Font)
         Font = f
      End Sub

      Public Overrides Function ToString() As String
         Return Font.Name
      End Function
   End Class
End Class

.NET Framework
Available since 1.1
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