ComboBoxRenderer.DrawDropDownButton Method

Definition

Namespace:

System.Windows.Forms

Assembly:

System.Windows.Forms.dll

Source:

ComboBoxRenderer.cs

Draws a drop-down arrow with the current visual style of the operating system.

C#

public static void DrawDropDownButton(System.Drawing.Graphics g, System.Drawing.Rectangle bounds, System.Windows.Forms.VisualStyles.ComboBoxState state);

Parameters

g

Graphics

The Graphics used to draw the drop-down arrow.

bounds

Rectangle

The Rectangle that specifies the bounds of the drop-down arrow.

state

ComboBoxState

One of the ComboBoxState values that specifies the visual state of the drop-down arrow.

Exceptions

InvalidOperationException

The operating system does not support visual styles.

-or-

Visual styles are disabled by the user in the operating system.

-or-

Visual styles are not applied to the client area of application windows.

Examples

The following code example uses the DrawDropDownButton method in a custom control's OnPaint method to draw a drop-down arrow in the state determined by the location of the mouse pointer. This code example is part of a larger example provided for the ComboBoxRenderer class.

C#

// Draw the combo box in the current state.
protected override void OnPaint(PaintEventArgs e)
{
    base.OnPaint(e);

    if (!ComboBoxRenderer.IsSupported)
    {
        this.Parent.Text = "Visual Styles Disabled";
        return;
    }

    this.Parent.Text = "CustomComboBox Enabled";

    // Always draw the main text box and drop down arrow in their 
    // current states
    ComboBoxRenderer.DrawTextBox(e.Graphics, topTextBoxRectangle,
        this.Text, this.Font, textBoxState);
    ComboBoxRenderer.DrawDropDownButton(e.Graphics, arrowRectangle,
        arrowState);

    // Only draw the bottom text box if the arrow has been clicked
    if (isActivated)
    {
        ComboBoxRenderer.DrawTextBox(e.Graphics,
            bottomTextBoxRectangle, bottomText, this.Font,
            textBoxState);
    }
}

protected override void OnMouseDown(MouseEventArgs e)
{
    base.OnMouseDown(e);

    // Check whether the user clicked the arrow.
    if (arrowRectangle.Contains(e.Location) &&
        ComboBoxRenderer.IsSupported)
    {
        // Draw the arrow in the pressed state.
        arrowState = ComboBoxState.Pressed;

        // The user has activated the combo box.
        if (!isActivated)
        {
            this.Text = "Clicked!";
            textBoxState = ComboBoxState.Pressed;
            isActivated = true;
        }

        // The user has deactivated the combo box.
        else
        {
            this.Text = "Click here";
            textBoxState = ComboBoxState.Normal;
            isActivated = false;
        }

        // Redraw the control.
        Invalidate();
    }
}

Remarks

Before calling this method, you should verify that the IsSupported property returns true.

Applies to