DataGridCheckBoxColumn.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / Framework / System / Windows / Controls / DataGridCheckBoxColumn.cs / 1305600 / DataGridCheckBoxColumn.cs
                        
                        
                            //---------------------------------------------------------------------------- 
//
// Copyright (C) Microsoft Corporation.  All rights reserved.
//
//--------------------------------------------------------------------------- 

using System; 
using System.ComponentModel; 
using System.Diagnostics;
using System.Windows; 
using System.Windows.Input;

namespace System.Windows.Controls
{ 
    /// 
    ///     A column that displays a check box. 
    ///  
    public class DataGridCheckBoxColumn : DataGridBoundColumn
    { 
        static DataGridCheckBoxColumn()
        {
            ElementStyleProperty.OverrideMetadata(typeof(DataGridCheckBoxColumn), new FrameworkPropertyMetadata(DefaultElementStyle));
            EditingElementStyleProperty.OverrideMetadata(typeof(DataGridCheckBoxColumn), new FrameworkPropertyMetadata(DefaultEditingElementStyle)); 
        }
 
        #region Styles 

        ///  
        ///     The default value of the ElementStyle property.
        ///     This value can be used as the BasedOn for new styles.
        /// 
        public static Style DefaultElementStyle 
        {
            get 
            { 
                if (_defaultElementStyle == null)
                { 
                    Style style = new Style(typeof(CheckBox));

                    // When not in edit mode, the end-user should not be able to toggle the state
                    style.Setters.Add(new Setter(UIElement.IsHitTestVisibleProperty, false)); 
                    style.Setters.Add(new Setter(UIElement.FocusableProperty, false));
                    style.Setters.Add(new Setter(CheckBox.HorizontalAlignmentProperty, HorizontalAlignment.Center)); 
                    style.Setters.Add(new Setter(CheckBox.VerticalAlignmentProperty, VerticalAlignment.Top)); 

                    style.Seal(); 
                    _defaultElementStyle = style;
                }

                return _defaultElementStyle; 
            }
        } 
 
        /// 
        ///     The default value of the EditingElementStyle property. 
        ///     This value can be used as the BasedOn for new styles.
        /// 
        public static Style DefaultEditingElementStyle
        { 
            get
            { 
                if (_defaultEditingElementStyle == null) 
                {
                    Style style = new Style(typeof(CheckBox)); 

                    style.Setters.Add(new Setter(CheckBox.HorizontalAlignmentProperty, HorizontalAlignment.Center));
                    style.Setters.Add(new Setter(CheckBox.VerticalAlignmentProperty, VerticalAlignment.Top));
 
                    style.Seal();
                    _defaultEditingElementStyle = style; 
                } 

                return _defaultEditingElementStyle; 
            }
        }

        #endregion 

        #region Element Generation 
 
        /// 
        ///     Creates the visual tree for boolean based cells. 
        /// 
        protected override FrameworkElement GenerateElement(DataGridCell cell, object dataItem)
        {
            return GenerateCheckBox(/* isEditing = */ false, cell); 
        }
 
        ///  
        ///     Creates the visual tree for boolean based cells.
        ///  
        protected override FrameworkElement GenerateEditingElement(DataGridCell cell, object dataItem)
        {
            return GenerateCheckBox(/* isEditing = */ true, cell);
        } 

        private CheckBox GenerateCheckBox(bool isEditing, DataGridCell cell) 
        { 
            CheckBox checkBox = (cell != null) ? (cell.Content as CheckBox) : null;
            if (checkBox == null) 
            {
                checkBox = new CheckBox();
            }
 
            checkBox.IsThreeState = IsThreeState;
 
            ApplyStyle(isEditing, /* defaultToElementStyle = */ true, checkBox); 
            ApplyBinding(checkBox, CheckBox.IsCheckedProperty);
 
            return checkBox;
        }

        protected internal override void RefreshCellContent(FrameworkElement element, string propertyName) 
        {
            DataGridCell cell = element as DataGridCell; 
            if (cell != null && 
                string.Compare(propertyName, "IsThreeState", StringComparison.Ordinal) == 0)
            { 
                var checkBox = cell.Content as CheckBox;
                if (checkBox != null)
                {
                    checkBox.IsThreeState = IsThreeState; 
                }
            } 
            else 
            {
                base.RefreshCellContent(element, propertyName); 
            }
        }

        #endregion 

        #region Editing 
 
        /// 
        ///     The DependencyProperty for the IsThreeState property. 
        ///     Flags:              None
        ///     Default Value:      false
        /// 
        public static readonly DependencyProperty IsThreeStateProperty = 
                CheckBox.IsThreeStateProperty.AddOwner(
                        typeof(DataGridCheckBoxColumn), 
                        new FrameworkPropertyMetadata(false, DataGridColumn.NotifyPropertyChangeForRefreshContent)); 

        ///  
        ///     The IsThreeState property determines whether the control supports two or three states.
        ///     IsChecked property can be set to null as a third state when IsThreeState is true
        /// 
        public bool IsThreeState 
        {
            get { return (bool)GetValue(IsThreeStateProperty); } 
            set { SetValue(IsThreeStateProperty, value); } 
        }
 
        /// 
        ///     Called when a cell has just switched to edit mode.
        /// 
        /// A reference to element returned by GenerateEditingElement. 
        /// The event args of the input event that caused the cell to go into edit mode. May be null.
        /// The unedited value of the cell. 
        protected override object PrepareCellForEdit(FrameworkElement editingElement, RoutedEventArgs editingEventArgs) 
        {
            CheckBox checkBox = editingElement as CheckBox; 
            if (checkBox != null)
            {
                checkBox.Focus();
                bool? uneditedValue = checkBox.IsChecked; 

                // If a click or a space key invoked the begin edit, then do an immediate toggle 
                if ((IsMouseLeftButtonDown(editingEventArgs) && IsMouseOver(checkBox, editingEventArgs)) || 
                    IsSpaceKeyDown(editingEventArgs))
                { 
                    checkBox.IsChecked = (uneditedValue != true);
                }

                return uneditedValue; 
            }
 
            return (bool?) false; 
        }
 
        internal override void OnInput(InputEventArgs e)
        {
            // Space key down will begin edit mode
            if (IsSpaceKeyDown(e)) 
            {
                BeginEdit(e); 
            } 
        }
 
        private static bool IsMouseLeftButtonDown(RoutedEventArgs e)
        {
            MouseButtonEventArgs mouseArgs = e as MouseButtonEventArgs;
            return (mouseArgs != null) && 
                   (mouseArgs.ChangedButton == MouseButton.Left) &&
                   (mouseArgs.ButtonState == MouseButtonState.Pressed); 
        } 

        private static bool IsMouseOver(CheckBox checkBox, RoutedEventArgs e) 
        {
            // This element is new, so the IsMouseOver property will not have been updated
            // yet, but there is enough information to do a hit-test.
            return checkBox.InputHitTest(((MouseButtonEventArgs)e).GetPosition(checkBox)) != null; 
        }
 
        private static bool IsSpaceKeyDown(RoutedEventArgs e) 
        {
            KeyEventArgs keyArgs = e as KeyEventArgs; 
            return (keyArgs != null) &&
                   ((keyArgs.KeyStates & KeyStates.Down) == KeyStates.Down) &&
                   (keyArgs.Key == Key.Space);
        } 

        #endregion 
 
        #region Data
 
        private static Style _defaultElementStyle;
        private static Style _defaultEditingElementStyle;

        #endregion 
    }
} 

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

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