c# - 如何从扩展的组合框类中禁用切换按钮

Question

我有一个扩展类Combobox。在这个类中，我只能禁用togglebutton. 我仍然希望用户单击combobox并输入内容以过滤其内容。

如果您知道任何其他销毁方法，togglebutton请告诉我（只要它不涉及重新创建模板 - 我已经尝试过但失败了，并且生成的combobox模板代码太大而无法转储到 stackoverflow 中，所以我无法解决就这样吧。）

一开始我希望能够切换togglebutton（如果过滤器中剩下的项目少于 10 个，则允许用户单击togglebutton以显示项目列表，如果有更多的切换按钮会消失）。在这一点上，我将采取缩小、隐藏、移动、故意破坏、移除、活埋、替换切换按钮或鼠标单击事件的任何解决方案，该事件告诉组合框它应该显示其弹出窗口或介于两者之间的任何内容停止这个动作。

这是我试图找到可行的方法的第三个问题。老实说，任何建议都会有所帮助（只是不要复制和编辑模板，请转到我的另一个问题，在那里我就如何实施该解决方案寻求帮助）

using Analytics_Module.Models;
using System;
using System.Collections;
using System.ComponentModel;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Controls.Primitives;
using System.Windows.Data;
using System.Windows.Input;
using System.Windows.Media;

namespace Analytics_Module.UI_Components
{
    class MultiselectFilteredComboBox : ComboBox
    {
        ////
        // Public Fields
        ////

        /// <summary>
        /// The search string treshold length.
        /// </summary>
        /// <remarks>
        /// It's implemented as a Dependency Property, so you can set it in a XAML template 
        /// </remarks>
        public static readonly DependencyProperty MinimumSearchLengthProperty =
            DependencyProperty.Register(
                "MinimumSearchLength",
                typeof(int),
                typeof(MultiselectFilteredComboBox),
                new UIPropertyMetadata(3));

        ////
        // Private Fields
        //// 

        /// <summary>
        /// Caches the previous value of the filter.
        /// </summary>
        private string oldFilter = string.Empty;

        /// <summary>
        /// Holds the current value of the filter.
        /// </summary>
        private string currentFilter = string.Empty;
        public static T FindChild<T>(DependencyObject parent, string childName)
   where T : DependencyObject
        {
            // Confirm parent and childName are valid. 
            if (parent == null) return null;

            T foundChild = null;

            int childrenCount = VisualTreeHelper.GetChildrenCount(parent);
            for (int i = 0; i < childrenCount; i++)
            {
                var child = VisualTreeHelper.GetChild(parent, i);
                // If the child is not of the request child type child
                T childType = child as T;
                if (childType == null)
                {
                    // recursively drill down the tree
                    foundChild = FindChild<T>(child, childName);

                    // If the child is found, break so we do not overwrite the found child. 
                    if (foundChild != null) break;
                }
                else if (!string.IsNullOrEmpty(childName))
                {
                    var frameworkElement = child as FrameworkElement;
                    // If the child's name is set for search
                    if (frameworkElement != null && frameworkElement.Name == childName)
                    {
                        // if the child's name is of the request name
                        foundChild = (T)child;
                        break;
                    }
                }
                else
                {
                    // child element found.
                    foundChild = (T)child;
                    break;
                }
            }

            return foundChild;
        }
        ////
        // Constructors
        //// 

        /// <summary>
        /// Initializes a new instance of the FilteredComboBox class.
        /// </summary>
        /// <remarks>
        /// You could set 'IsTextSearchEnabled' to 'false' here,
        /// to avoid non-intuitive behavior of the control
        /// </remarks>
        public MultiselectFilteredComboBox()
        {

        }

        ////
        // Properties
        //// 

        /// <summary>
        /// Gets or sets the search string treshold length.
        /// </summary>
        /// <value>The minimum length of the search string that triggers filtering.</value>
        [Description("Length of the search string that triggers filtering.")]
        [Category("Filtered ComboBox")]
        [DefaultValue(3)]
        public int MinimumSearchLength
        {
            [System.Diagnostics.DebuggerStepThrough]
            get
            {
                return (int)this.GetValue(MinimumSearchLengthProperty);
            }

            [System.Diagnostics.DebuggerStepThrough]
            set
            {
                this.SetValue(MinimumSearchLengthProperty, value);
            }
        }

        /// <summary>
        /// Gets a reference to the internal editable textbox.
        /// </summary>
        /// <value>A reference to the internal editable textbox.</value>
        /// <remarks>
        /// We need this to get access to the Selection.
        /// </remarks>
        protected TextBox EditableTextBox
        {
            get
            {
                return this.GetTemplateChild("PART_EditableTextBox") as TextBox;
            }
        }

        ////
        // Event Raiser Overrides
        //// 

        /// <summary>
        /// Keep the filter if the ItemsSource is explicitly changed.
        /// </summary>
        /// <param name="oldValue">The previous value of the filter.</param>
        /// <param name="newValue">The current value of the filter.</param>
        protected override void OnItemsSourceChanged(IEnumerable oldValue, IEnumerable newValue)
        {
            if (newValue != null)
            {
                ICollectionView view = CollectionViewSource.GetDefaultView(newValue);
                view.Filter += this.FilterPredicate;
            }

            if (oldValue != null)
            {
                ICollectionView view = CollectionViewSource.GetDefaultView(oldValue);
                view.Filter -= this.FilterPredicate;
            }

            base.OnItemsSourceChanged(oldValue, newValue);
        }

        /// <summary>
        /// Confirm or cancel the selection when Tab, Enter, or Escape are hit. 
        /// Open the DropDown when the Down Arrow is hit.
        /// </summary>
        /// <param name="e">Key Event Args.</param>
        /// <remarks>
        /// The 'KeyDown' event is not raised for Arrows, Tab and Enter keys.
        /// It is swallowed by the DropDown if it's open.
        /// So use the Preview instead.
        /// </remarks>
        protected override void OnPreviewKeyDown(KeyEventArgs e)
        {
            if (e.Key == Key.Tab || e.Key == Key.Enter)
            {
                // Explicit Selection -> Close ItemsPanel
                this.IsDropDownOpen = false;
            }
            else if (e.Key == Key.Escape)
            {
                // Escape -> Close DropDown and redisplay Filter
                this.IsDropDownOpen = false;
                this.SelectedIndex = -1;
                this.Text = this.currentFilter;
            }
            else
            {
                if (e.Key == Key.Down)
                {
                    // Arrow Down -> Open DropDown
                    this.IsDropDownOpen = true;
                }

                base.OnPreviewKeyDown(e);
            }

            // Cache text
            this.oldFilter = this.Text;
        }

        /// <summary>
        /// Modify and apply the filter.
        /// </summary>
        /// <param name="e">Key Event Args.</param>
        /// <remarks>
        /// Alternatively, you could react on 'OnTextChanged', but navigating through 
        /// the DropDown will also change the text.
        /// </remarks>
        protected override void OnKeyUp(KeyEventArgs e)
        {
            if (e.Key == Key.Up || e.Key == Key.Down)
            {
                // Navigation keys are ignored
            }
            else if (e.Key == Key.Tab || e.Key == Key.Enter)
            {
                // Explicit Select -> Clear Filter
                this.ClearFilter();
            }
            else
            {
                // The text was changed
                if (this.Text != this.oldFilter)
                {
                    // Clear the filter if the text is empty,
                    // apply the filter if the text is long enough
                    if (this.Text.Length == 0 || this.Text.Length >= this.MinimumSearchLength)
                    {
                        this.RefreshFilter();
                        this.IsDropDownOpen = true;

                        // Unselect
                        this.EditableTextBox.SelectionStart = int.MaxValue;
                    }
                }

                base.OnKeyUp(e);

                // Update Filter Value
                this.currentFilter = this.Text;
            }
        }

        /// <summary>
        /// Make sure the text corresponds to the selection when leaving the control.
        /// </summary>
        /// <param name="e">A KeyBoardFocusChangedEventArgs.</param>
        protected override void OnPreviewLostKeyboardFocus(KeyboardFocusChangedEventArgs e)
        {
            //this.ClearFilter();
            //int temp = this.SelectedIndex;
            //this.SelectedIndex = -1;
            //this.Text = string.Empty;
            //this.SelectedIndex = temp;
            //base.OnPreviewLostKeyboardFocus(e);
        }

        ////
        // Helpers
        ////

        /// <summary>
        /// Re-apply the Filter.
        /// </summary>
        private void RefreshFilter()
        {
            if (this.ItemsSource != null)
            {
                ICollectionView view = CollectionViewSource.GetDefaultView(this.ItemsSource);
                view.Refresh();
            }
        }

        /// <summary>
        /// Clear the Filter.
        /// </summary>
        private void ClearFilter()
        {
            this.currentFilter = string.Empty;
            this.RefreshFilter();
        }

        /// <summary>
        /// The Filter predicate that will be applied to each row in the ItemsSource.
        /// </summary>
        /// <param name="value">A row in the ItemsSource.</param>
        /// <returns>Whether or not the item will appear in the DropDown.</returns>
        private bool FilterPredicate(object value)
        {
            MultiSelectDropDownListEntry tmp = (MultiSelectDropDownListEntry)value;

            // No filter, no text
            if (value == null)
            {
                return false;
            }

            // No text, no filter
            if (this.Text.Length == 0)
            {
                return true;
            }

            // Case insensitive search
            return tmp.Name.ToString().ToLower().Contains(this.Text.ToLower());
        }
    }
}

标签： c#wpfclasscombobox

Answer 1

找到了办法。

我在课堂上添加了这个

    public override void OnApplyTemplate()
    {
        base.OnApplyTemplate();
        (((this.GetVisualChild(0) as Grid).Children)[1] as System.Windows.Controls.Primitives.ToggleButton).IsEnabled = false;
    }