DropDownHolder.cs source code in C# .NET

                        Code:
                         / FX-1434 / FX-1434 / 1.0 / untmp / whidbey / REDBITS / ndp / fx / src / Designer / WinForms / System / WinForms / Design / DropDownHolder.cs / 1 / DropDownHolder.cs
                        
                        
                            namespace System.Windows.Forms.Design { 

    using Microsoft.Win32;
    using System.Collections;
    using System.ComponentModel; 
    using System.ComponentModel.Design;
    using System.Design; 
    using System.Diagnostics; 
    using System.Drawing.Drawing2D;
    using System.Drawing; 
    using System.Windows.Forms;
    using System.Runtime.InteropServices;
    using System.Diagnostics.CodeAnalysis;
 
    internal class DropDownHolder : Form {
 
        private Control parent; 
        private Control currentControl = null;
        private const int BORDER = 1; 

        [SuppressMessage("Microsoft.Globalization", "CA1303:DoNotPassLiteralsAsLocalizedParameters")]
        public DropDownHolder(Control parent)
        : base() { 
           this.parent = parent;
           this.ShowInTaskbar = false; 
           this.ControlBox = false; 
           this.MinimizeBox = false;
           this.MaximizeBox = false; 
           this.Text = "";
           this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.FixedToolWindow;
           this.StartPosition = FormStartPosition.Manual;
           this.Font = parent.Font; 
           Visible = false;
           this.BackColor = SystemColors.Window; 
        } 

        protected override CreateParams CreateParams { 
            get {
                CreateParams cp = base.CreateParams;
                cp.ExStyle |= NativeMethods.WS_EX_TOOLWINDOW;
                cp.Style |= NativeMethods.WS_POPUP | NativeMethods.WS_BORDER; 
                if (this.parent != null) {
                    cp.Parent = this.parent.Handle; 
                } 
                return cp;
            } 
        }

        // Lifted directly from PropertyGridView.DropDownHolder. Less destructive than using ShowDialog().
        // 
        public void DoModalLoop() {
 
                while (this.Visible) { 
                    Application.DoEvents();
                    UnsafeNativeMethods.MsgWaitForMultipleObjects(0, IntPtr.Zero, true, 250, NativeMethods.QS_ALLINPUT); 
                }
        }

        public virtual Control Component { 
            get {
                return currentControl; 
            } 
        }
 
        public virtual bool GetUsed() {
            return(currentControl != null);
        }
 
        protected override void OnMouseDown(MouseEventArgs me) {
           if (me.Button == MouseButtons.Left) { 
              Visible = false; 
           }
           base.OnMouseDown(me); 
        }

        /// 
        ///    General purpose method, based on Control.Contains()... 
        ///
        ///    Determines whether a given window (specified using native window handle) 
        ///    is a descendant of this control. This catches both contained descendants 
        ///    and 'owned' windows such as modal dialogs. Using window handles rather
        ///    than Control objects allows it to catch un-managed windows as well. 
        /// 
        private bool OwnsWindow(IntPtr hWnd) {
            while (hWnd != IntPtr.Zero) {
                hWnd = UnsafeNativeMethods.GetWindowLong(new HandleRef(null, hWnd), NativeMethods.GWL_HWNDPARENT); 
                if (hWnd == IntPtr.Zero) {
                    return false; 
                } 
                if (hWnd == this.Handle) {
                    return true; 
                }
            }
            return false;
        } 

        /* 
        protected override void SetBoundsCore(int x, int y, int width, int height, BoundsSpecified specified) { 
            if (currentControl != null) {
                currentControl.SetBounds(0, 0, width - 2 * BORDER, height - 2 * BORDER); 
                width = currentControl.Width;
                height = currentControl.Height;
                if (height == 0 && currentControl is ListBox) {
                    height = ((ListBox)currentControl).ItemHeight; 
                    currentControl.Height = height;
                } 
                width += 2 * BORDER; 
                height += 2 * BORDER;
            } 
            base.SetBoundsCore(x, y, width, height, specified);
        } */

        public virtual void FocusComponent() { 
            if (currentControl != null && Visible) {
                //currentControl.FocusInternal(); 
                currentControl.Focus(); 
            }
        } 

        private void OnCurrentControlResize(object o, EventArgs e) {
            if (currentControl != null) {
                int oldWidth = this.Width; 
                UpdateSize();
                currentControl.Location = new Point(BORDER, BORDER); 
                this.Left -= (this.Width - oldWidth); 
            }
        } 

        protected override bool ProcessDialogKey(Keys keyData) {
            if ((keyData & (Keys.Shift | Keys.Control | Keys.Alt)) == 0) {
                switch (keyData & Keys.KeyCode) { 
                    case Keys.Escape:
                        Visible = false; 
                        return true; 
                    case Keys.F4:
                        //dataGridView.F4Selection(true); 
                        return true;
                    case Keys.Return:
                        // make sure the return gets forwarded to the control that
                        // is being displayed 
                        //if (dataGridView.UnfocusSelection()) {
                          //dataGridView.SelectedGridEntry.OnValueReturnKey(); 
                        //} 
                        return true;
                } 
            }

            return base.ProcessDialogKey(keyData);
        } 

        public virtual void SetComponent(Control ctl) { 
 
            if (currentControl != null) {
                Controls.Remove(currentControl); 
                currentControl = null;
            }
            if (ctl != null) {
                Controls.Add(ctl); 
                ctl.Location = new Point(BORDER, BORDER);
                ctl.Visible = true; 
                currentControl = ctl; 
                UpdateSize();
                currentControl.Resize += new EventHandler(this.OnCurrentControlResize); 
            }
            Enabled = currentControl != null;
        }
 
        private void UpdateSize() {
            Size = new Size(2 * BORDER + currentControl.Width + 2, 2 * BORDER + currentControl.Height + 2); 
        } 

        protected override void WndProc(ref Message m) { 

            if (m.Msg == NativeMethods.WM_ACTIVATE &&
                Visible &&
                NativeMethods.Util.LOWORD((int)m.WParam) == NativeMethods.WA_INACTIVE && 
                !this.OwnsWindow((IntPtr) m.LParam)) {
 
                Visible = false; 
                return;
            } 

            /*
            else if (m.Msg == NativeMethods.WM_CLOSE) {
                // don't let an ALT-F4 get you down 
                //
                if (Visible) { 
                    //dataGridView.CloseDropDown(); 
                }
                return; 
            } */

            base.WndProc(ref m);
        } 
    }
} 
 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
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DropDownHolder.cs source code in C# .NET

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