[DXCategory("Layout")]
public override DockStyle Dock { get; set; }

<DXCategory("Layout")>
Public Overrides Property Dock As DockStyle

using DevExpress.XtraEditors;
using DevExpress.XtraEditors.Controls;
using DevExpress.XtraGrid;
using DevExpress.XtraGrid.Views.Grid;
using DevExpress.XtraTreeList;
using System.Windows.Forms;

namespace DXApplication {
    public partial class Form1 : DevExpress.XtraBars.Ribbon.RibbonForm {
        RoundedSkinPanel roundedSkinPanel1, roundedSkinPanel2, roundedSkinPanel3;
        GridControl gridControl1, gridControl2;
        public Form1() {
            InitializeComponent();
            // Create the first GridControl
            GridControl gridControl1 = new GridControl() { Dock = DockStyle.Fill };
            // Assign a GridView to the first GridControl.
            gridControl1.MainView = new GridView();
            // Create the first RoundedSkinPanel and set it to fill the form.
            roundedSkinPanel1 = new RoundedSkinPanel() { Dock = DockStyle.Fill };
            // Add the GridControl to the first panel.
            roundedSkinPanel1.Controls.Add(gridControl1);

            // Create a TreeList.
            TreeList treeList1 = new TreeList() { Dock = DockStyle.Fill };
            // Create the second RoundedSkinPanel, dock it to the left, and set its width.
            roundedSkinPanel2 = new RoundedSkinPanel() { Dock = DockStyle.Left, Width = 300 };
            // Add the TreeList to the second panel.
            roundedSkinPanel2.Controls.Add(treeList1);

            // Create the second GridControl.
            GridControl gridControl2 = new GridControl() { Dock = DockStyle.Fill };
            // Assign a GridView to the second GridControl.
            gridControl2.MainView = new GridView() { BorderStyle = BorderStyles.NoBorder };
            // Create the third RoundedSkinPanel, dock it to the bottom, and set its height.
            roundedSkinPanel3 = new RoundedSkinPanel() { Dock = DockStyle.Bottom, Height = 200 };
            // Add the second GridControl to the third panel.
            roundedSkinPanel3.Controls.Add(gridControl2);

            // Add the bottom panel and the left panel to the first panel.
            roundedSkinPanel1.Controls.Add(roundedSkinPanel3);
            roundedSkinPanel1.Controls.Add(roundedSkinPanel2);

            // Add the first panel (containing all other panels) to the form.
            this.Controls.Add(roundedSkinPanel1);
        }

    }
}

Imports DevExpress.XtraEditors
Imports DevExpress.XtraEditors.Controls
Imports DevExpress.XtraGrid
Imports DevExpress.XtraGrid.Views.Grid
Imports DevExpress.XtraTreeList
Imports System.Windows.Forms

Namespace DXApplication
    Public Partial Class Form1
        Inherits DevExpress.XtraBars.Ribbon.RibbonForm

        Private roundedSkinPanel1 As RoundedSkinPanel
        Private roundedSkinPanel2 As RoundedSkinPanel
        Private roundedSkinPanel3 As RoundedSkinPanel
        Private gridControl1 As GridControl
        Private gridControl2 As GridControl

        Public Sub New()
            InitializeComponent()
            ' Create the first GridControl
            gridControl1 = New GridControl() With {.Dock = DockStyle.Fill}
            ' Assign a GridView to the first GridControl.
            gridControl1.MainView = New GridView()
            ' Create the first RoundedSkinPanel and set it to fill the form.
            roundedSkinPanel1 = New RoundedSkinPanel() With {.Dock = DockStyle.Fill}
            ' Add the GridControl to the first panel.
            roundedSkinPanel1.Controls.Add(gridControl1)

            ' Create a TreeList with no border
            Dim treeList1 As New TreeList() With {.Dock = DockStyle.Fill}
            ' Create the second RoundedSkinPanel, dock it to the left, and set its width.
            roundedSkinPanel2 = New RoundedSkinPanel() With {.Dock = DockStyle.Left, .Width = 300}
            ' Add the TreeList to the second panel.
            roundedSkinPanel2.Controls.Add(treeList1)

            ' Create the second GridControl.
            gridControl2 = New GridControl() With {.Dock = DockStyle.Fill}
            ' Assign a GridView to the second GridControl.
            gridControl2.MainView = New GridView()
            ' Create the third RoundedSkinPanel, dock it to the bottom, and set its height.
            roundedSkinPanel3 = New RoundedSkinPanel() With {.Dock = DockStyle.Bottom, .Height = 200}
            ' Add the second GridControl to the third panel.
            roundedSkinPanel3.Controls.Add(gridControl2)

            ' Add the bottom panel and the left panel to the first panel.
            roundedSkinPanel1.Controls.Add(roundedSkinPanel3)
            roundedSkinPanel1.Controls.Add(roundedSkinPanel2)

            ' Add the first panel (containing all other panels) to the form.
            Me.Controls.Add(roundedSkinPanel1)
        End Sub

    End Class
End Namespace