ComboBox.DropDownStyle Propriedade
Definição
Importante
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Obtém ou define um valor que especifica o estilo da caixa de combinação.
public:
property System::Windows::Forms::ComboBoxStyle DropDownStyle { System::Windows::Forms::ComboBoxStyle get(); void set(System::Windows::Forms::ComboBoxStyle value); };public System.Windows.Forms.ComboBoxStyle DropDownStyle { get; set; }member this.DropDownStyle : System.Windows.Forms.ComboBoxStyle with get, setPublic Property DropDownStyle As ComboBoxStyleValor da propriedade
Um dos valores de ComboBoxStyle. O padrão é DropDown.
Exceções
O valor atribuído não é um dos valores ComboBoxStyle.
Exemplos
O exemplo de código a seguir demonstra a configuração da DropDownStyle propriedade. Para executar o exemplo, cole o código a seguir em um formulário. Chame o InitializeComboBox método no construtor ou Load evento do formulário.
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
Comentários
A DropDownStyle propriedade especifica se a lista sempre é exibida ou se a lista é exibida em uma lista suspensa. A DropDownStyle propriedade também especifica se a parte do texto pode ser editada. Confira ComboBoxStyle as configurações disponíveis e seus efeitos. Não há nenhuma configuração para sempre exibir a lista e não permitir a inserção de um novo valor. Para exibir uma lista à qual nenhum novo valor pode ser adicionado, use um ListBox controle .
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