public bool ShowSeparator {get; set;}

private void InitializeComboFrameDropDowSettings()
{
    // Sets the AutoDropDown to true to open the gcComboFrame1's drop-down window automatically
    // after the control gets focus.
    this.gcComboFrame1.DropDownSettings.AutoDropDown = true;

    // Set drop-down windows's size .
    this.gcComboFrame1.DropDownSettings.Size = new Size(this.gcComboFrame1.Width, 100);

    // Set AllowResize to true to enable user UI resizes the drop-down window by sizing grip.
    this.gcComboFrame1.DropDownSettings.AllowResize = true;

    // Opens the drop-down window from the below-right of gcComboFrame1.
    this.gcComboFrame1.DropDownSettings.DropDownDirection = DropDownDirection.BelowRight;

    // Set the opening and closing animation for the drop-down window.
    this.gcComboFrame1.DropDownSettings.OpeningAnimation = DropDownAnimation.Fade;
    this.gcComboFrame1.DropDownSettings.ClosingAnimation = DropDownAnimation.Fade;

    // Hide the separator between the content of the drop-down window and the resizing grip.
    this.gcComboFrame1.DropDownSettings.ShowSeparator = false;

    // Sets the BorderStyle of the drop-down window.
    this.gcComboFrame1.DropDownSettings.BorderStyle = BorderStyle.FixedSingle;

    // Sets the color of the border of drop-down window.
    this.gcComboFrame1.DropDownSettings.SingleBorderColor = Color.Black;

    // Enables the shadow effect of the drop-down window.
    this.gcComboFrame1.DropDownSettings.ShowShadow = true;
}