ComboBox.DropDown Événement

Définition

Espace de noms:

System.Windows.Forms

Assembly:

System.Windows.Forms.dll

Se produit quand la partie déroulante d’un ComboBox est affichée.

public:
 event EventHandler ^ DropDown;

public event EventHandler? DropDown;

member this.DropDown : EventHandler 

Public Custom Event DropDown As EventHandler 

Type d'événement

EventHandler

Exemples

L’exemple de code suivant montre comment initialiser un ComboBox contrôle en définissant la propriété text et en utilisant la AddRange méthode pour remplir le ComboBox. Il illustre également la gestion de l’événement DropDown . Pour exécuter l’exemple, collez le code suivant dans un formulaire et appelez la InitializeComboBox méthode dans le constructeur ou Load l’événement du formulaire.

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

private:
   // Initialize ComboBox1.
   void InitializeComboBox()
   {
      this->ComboBox1 = gcnew ComboBox;
      this->ComboBox1->Location = System::Drawing::Point( 128, 48 );
      this->ComboBox1->Name = "ComboBox1";
      this->ComboBox1->Size = System::Drawing::Size( 100, 21 );
      this->ComboBox1->TabIndex = 0;
      this->ComboBox1->Text = "Typical";
      array<String^>^ installs = {"Typical","Compact","Custom"};
      ComboBox1->Items->AddRange( installs );
      this->Controls->Add( this->ComboBox1 );
      
      // Hook up the event handler.
      this->ComboBox1->DropDown += gcnew System::EventHandler(
         this, &Form1::ComboBox1_DropDown );
   }

   // Handles the ComboBox1 DropDown event. If the user expands the  
   // drop-down box, a message box will appear, recommending the
   // typical installation.
   void ComboBox1_DropDown( Object^ sender, System::EventArgs^ e )
   {
      MessageBox::Show( "Typical installation is strongly recommended.",
         "Install information", MessageBoxButtons::OK,
         MessageBoxIcon::Information );
   }

// Declare ComboBox1.
internal System.Windows.Forms.ComboBox ComboBox1;

// Initialize ComboBox1.
private void InitializeComboBox()
{
    this.ComboBox1 = new ComboBox();
    this.ComboBox1.Location = new System.Drawing.Point(128, 48);
    this.ComboBox1.Name = "ComboBox1";
    this.ComboBox1.Size = new System.Drawing.Size(100, 21);
    this.ComboBox1.TabIndex = 0;
    this.ComboBox1.Text	= "Typical";
    string[] installs = new string[]{"Typical", "Compact", "Custom"};
    ComboBox1.Items.AddRange(installs);
    this.Controls.Add(this.ComboBox1);
    
    // Hook up the event handler.
    this.ComboBox1.DropDown +=  
        new System.EventHandler(ComboBox1_DropDown);
}

// Handles the ComboBox1 DropDown event. If the user expands the  
// drop-down box, a message box will appear, recommending the
// typical installation.
private void ComboBox1_DropDown(object sender, System.EventArgs e)
{
    MessageBox.Show("Typical installation is strongly recommended.", 
    "Install information", MessageBoxButtons.OK, 
        MessageBoxIcon.Information);
}

' Declare ComboBox1.
Friend WithEvents ComboBox1 As System.Windows.Forms.ComboBox

' Initialize ComboBox1.
Private Sub InitializeComboBox()
    Me.ComboBox1 = New ComboBox
    Me.ComboBox1.Location = New System.Drawing.Point(128, 48)
    Me.ComboBox1.Name = "ComboBox1"
    Me.ComboBox1.Size = New System.Drawing.Size(100, 21)
    Me.ComboBox1.TabIndex = 0
    Me.ComboBox1.Text = "Typical"
    Dim installs() As String = New String() _
        {"Typical", "Compact", "Custom"}
    ComboBox1.Items.AddRange(installs)
    Me.Controls.Add(Me.ComboBox1)
End Sub

' Handles the ComboBox1 DropDown event. If the user expands the  
' drop-down box, a message box will appear, recommending the
' typical installation.
Private Sub ComboBox1_DropDown _ 
    (ByVal sender As Object, ByVal e As System.EventArgs) _ 
    Handles ComboBox1.DropDown
    MessageBox.Show("Typical installation is strongly recommended.", _
    "Install information", MessageBoxButtons.OK, MessageBoxIcon.Information)
End Sub

Remarques

Pour plus d'informations sur la gestion des événements, voir gestion et déclenchement d’événements.

Voir aussi

• DropDownClosed