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ComboBox.DropDown Event

Occurs when the drop-down portion of a ComboBox is shown.

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

public event EventHandler DropDown

For more information about handling events, see Consuming Events.

The following code example demonstrates how to initialize a ComboBox control by setting the text property and using the AddRange method to populate the ComboBox. It also demonstrates handling the DropDown event. To run the example, paste the following code in a form and call the InitializeComboBox method in the form's constructor or Load event.

	// 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);
	}

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

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

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

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