ComboBox.DropDownWidth Свойство

Определение

Пространство имен:

System.Windows.Forms

Сборка:

System.Windows.Forms.dll

Возвращает или задает ширину раскрывающейся части поля со списком.

public:
 property int DropDownWidth { int get(); void set(int value); };

public int DropDownWidth { get; set; }

member this.DropDownWidth : int with get, set

Public Property DropDownWidth As Integer

Значение свойства

Int32

Ширина раскрывающегося поля в пикселях.

Исключения

ArgumentException

Указанное значение меньше единицы.

Примеры

В следующем примере кода показано, как создать поле со списком, нарисованное владельцем, задав DrawMode свойству OwnerDrawnVariable значение и обрабатывая DrawItem события и MeasureItem . Здесь также показано задание DropDownWidth свойств и DropDownStyle . Чтобы выполнить пример, вставьте следующий код в форму. InitializeComboBox Вызовите метод в конструкторе или Load событии формы.

internal:
   System::Windows::Forms::ComboBox^ ComboBox1;

private:
   array<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.
   void InitializeComboBox()
   {
      this->ComboBox1 = gcnew ComboBox;
      this->ComboBox1->DrawMode = System::Windows::Forms::DrawMode::OwnerDrawVariable;
      this->ComboBox1->Location = System::Drawing::Point( 10, 20 );
      this->ComboBox1->Name = "ComboBox1";
      this->ComboBox1->Size = System::Drawing::Size( 100, 120 );
      this->ComboBox1->DropDownWidth = 250;
      this->ComboBox1->TabIndex = 0;
      this->ComboBox1->DropDownStyle = ComboBoxStyle::DropDown;
      animals = gcnew array<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 +=
         gcnew DrawItemEventHandler( this, &Form1::ComboBox1_DrawItem );
      this->ComboBox1->MeasureItem +=
         gcnew MeasureItemEventHandler( this, &Form1::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;
   }

private:
   // 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.
   void ComboBox1_DrawItem( Object^ sender,
      System::Windows::Forms::DrawItemEventArgs^ e )
   {
      float size = 0;
      System::Drawing::Font^ myFont;
      FontFamily^ family = nullptr;

      System::Drawing::Color animalColor;
      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 = Rectangle( 2, e->Bounds.Top + 2,
         e->Bounds.Height, e->Bounds.Height - 4 );
      e->Graphics->FillRectangle( gcnew SolidBrush( animalColor ), rectangle );
      
      // Draw each string in the array, using a different size, color,
      // and font for each item.
      myFont = gcnew System::Drawing::Font( family, size, FontStyle::Bold );
      e->Graphics->DrawString( animals[ e->Index ], myFont,
         System::Drawing::Brushes::Black, 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();
   }

  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();
  }

  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.
  Private 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

Комментарии

Если значение не задано для DropDownWidth, это свойство возвращает Width значение поля со списком.

Примечание

Ширина раскрывающегося списка не может быть меньше ширины ComboBox .