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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 Handling and Raising 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);
	}

.NET Framework

Supported in: 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

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