C＃在列表框上禁用Ctrl鍵

Question

我想禁用ListBox上的Ctrl鍵。 我按照D＆D中的禁用列表框CTRL + C＆CTRL + X的示例進行操作。 因為我正在using System.Windows.Input和using System.Windows.Forms ，所以花了一些時間。 我能夠解析引用，除了e對象。 它告訴我System.Windows.Forms.PreviewKeyDownEventArgs沒有Handled定義。 我在這里想念什么？ 謝謝！

  private void lbSigns_PreviewKeyDown(object sender, 
                System.Windows.Forms.PreviewKeyDownEventArgs e)
    {
        //
        // This if statement detects if the Control Key is pressed.
        //
        if ((System.Windows.Input.Keyboard.Modifiers & 
          System.Windows.Input.ModifierKeys.Control) == 
                 System.Windows.Input.ModifierKeys.Control)
        {
            e.Handled = true;
        }
    }

好的，我與@Tsukasa的代碼越來越接近。 這就是我現在所擁有的。

    List<int> alreadySelectedIndexes = new List<int>();

    private void lbSigns_SelectedIndexChanged(object sender, EventArgs e)
    {

        TrackSelection((ListBox)sender, alreadySelectedIndexes);

        bool allowSelection = false;

        int currentSelectedIndex = -1;

        //make sure we have an item selected
        if (!lbSigns.SelectedIndex.Equals(-1))
        {
            //if first selection we allow it
            if (alreadySelectedIndexes.Count.Equals(1))
            {
                allowSelection = true;
            }
            else
            {
                //get the last item index that was selected from our list
                currentSelectedIndex = alreadySelectedIndexes[alreadySelectedIndexes.Count - 1];

                //make sure we have a previous index item
                if ((currentSelectedIndex - 1) >= 0)
                {
                    //check if previous item before currently selected is checked
                    if (lbSigns.GetSelected(currentSelectedIndex - 1))
                    {
                        allowSelection = true;
                    }
                }

                //make sure we have a next index item
                if ((currentSelectedIndex + 1) <= lbSigns.Items.Count - 1)
                {
                    //check if next item after currently selected is checked
                    if (lbSigns.GetSelected(currentSelectedIndex + 1))
                    {
                        allowSelection = true;
                    }
                }
                //make sure we have both a next and a previous item
                if (((currentSelectedIndex - 1) >= 0) && ((currentSelectedIndex + 1) <= lbSigns.Items.Count - 1))
                {
                    //if both are selected, deny the selection
                    if (lbSigns.GetSelected(currentSelectedIndex - 1) && lbSigns.GetSelected(currentSelectedIndex + 1))
                    {
                        allowSelection = false;
                    }
                }
            }
        }

        //unselect item because it wasn't before or after an already selected item
        if (!allowSelection && !currentSelectedIndex.Equals(-1))
        {
            lbSigns.SetSelected(currentSelectedIndex, false);
        }
    }

    private void TrackSelection(ListBox listBox, List<int> alreadySelectedList)
    {
        ListBox.SelectedIndexCollection indexCollection = listBox.SelectedIndices;

        foreach (int index in indexCollection)
        {
            if (!alreadySelectedList.Contains(index))
            {
                alreadySelectedList.Add(index);
            }
        }

        foreach (int index in new List<int>(alreadySelectedList))
        {
            if (!indexCollection.Contains(index))
            {
                alreadySelectedList.Remove(index);
            }
        }
    }

但是，這讓我取消選擇了2個選定項目周圍的項目。 取消選擇后，即使它已在任一側選擇了項目，也不允許我重新選擇該項目。 我在注釋后面的部分中添加了： //make sure we have both a next and a previous item

Answer 1

更新2

好的，這不允許在選定的項目之間取消選擇，盡管還有另一個問題。

問題：您可以按住鼠標按鈕，向左按住Ctrl +鼠標並上下拖動。 直到完成，才調用該事件。 我不確定要嘗試糾正哪個事件。

不過，我確實有更好的方式可以稍后發布。 我將在左右控制鍵上都創建一個全局鍵盤鈎。 如果檢測到該鍵時觸發。 如果ListBox具有輸入焦點，則我們將處理該鍵，從而僅使Shift按鈕能夠用於選擇多個項目。 您要確保僅當輸入焦點位於ListBox上時，否則它將成為所有其他應用程序的鍵，因為它是全局鈎子。

        //hold already selected items. Last item will be last selected
    List<int> alreadySelectedIndexes = new List<int>();

    //used to skip listBox1_SelectedIndexChanged on TrackSelection
    bool ignoreSelectedChanged = false;

    private void listBox1_SelectedIndexChanged(object sender, EventArgs e)
    {
        //prevent overflow of caused by TrackSelection
        if (!ignoreSelectedChanged)
        {
            TrackSelection((ListBox)sender, alreadySelectedIndexes);

            bool allowSelection = false;

            int currentSelectedIndex = -1;

            //make sure we have an item selected
            if (!listBox1.SelectedIndex.Equals(-1))
            {
                //if first selection we allow it
                if (alreadySelectedIndexes.Count.Equals(1))
                {
                    allowSelection = true;
                }
                else
                {
                    //get the last item index that was selected from our list
                    if ((alreadySelectedIndexes.Count - 1) >= 0)
                    {
                        currentSelectedIndex = alreadySelectedIndexes[alreadySelectedIndexes.Count - 1];

                        //make sure we stay in array range
                        if ((currentSelectedIndex - 1) >= 0)
                        {
                            //check if previous item before currently selected is checked
                            if (listBox1.GetSelected(currentSelectedIndex - 1))
                            {
                                allowSelection = true;
                            }
                        }

                        //make sure we stay in array range
                        if ((currentSelectedIndex + 1) <= listBox1.Items.Count - 1)
                        {
                            //check if next item after currently selected is checked
                            if (listBox1.GetSelected(currentSelectedIndex + 1))
                            {
                                allowSelection = true;
                            }
                        }
                    }
                }

                bool isSelected = false;
                if (currentSelectedIndex >= 0)
                {
                    isSelected = listBox1.GetSelected(currentSelectedIndex);

                    if (!isSelected)
                    {
                        //we can remove it from the list now
                        alreadySelectedIndexes.Remove(currentSelectedIndex);

                        //reselect it if in the middle of already selected items
                        if (alreadySelectedIndexes.Contains(currentSelectedIndex + 1) && alreadySelectedIndexes.Contains(currentSelectedIndex - 1))
                        {
                            ignoreSelectedChanged = true;
                            allowSelection = true;
                            listBox1.SetSelected(currentSelectedIndex, true);
                        }
                    }
                }
            }

            if (!currentSelectedIndex.Equals(-1) && !allowSelection)
            {
                ignoreSelectedChanged = true;
                listBox1.SetSelected(currentSelectedIndex, false);
            }

            //unselect item because it wasn't before or after the last selected item

        }
        ignoreSelectedChanged = false;
    }

    private void TrackSelection(ListBox listBox, List<int> alreadySelectedList)
    {
        ListBox.SelectedIndexCollection indexCollection = listBox.SelectedIndices;

            foreach (int index in indexCollection)
            {
                if (!alreadySelectedList.Contains(index))
                {
                    alreadySelectedList.Add(index);
                }
            }

        foreach (int index in new List<int>(alreadySelectedList))
        {
            if (!indexCollection.Contains(index))
            {
                //remove first index in list
                alreadySelectedList.Remove(index);
                //add index back to end of list so we know what was deselected
                alreadySelectedList.Add(index);
            }
        }
    }

Answer 2

            using System;
            using System.Collections.Generic;
            using System.ComponentModel;
            using System.Data;
            using System.Drawing;
            using System.Linq;
            using System.Text;
            using System.Threading.Tasks;
            using System.Windows.Forms;

            namespace listBoxWinforms
            {
                public partial class Form1 : Form
                {
                    public Form1()
                    {
                        InitializeComponent();
                    }

                    private void listBox1_PreviewKeyDown(object sender, PreviewKeyDownEventArgs e)
                    {
                        if (e.Control)
                        {
                            return;
                        }
                    }
                }
            }