C#和Winforms TextBox控件:如何更改文本？

Question

我在我的表单上有一个TextBox.TextChanged事件的事件处理程序.为了支持撤销,我想弄清楚TextBox中究竟发生了哪些变化,以便我可以在用户要求时撤消更改.(我知道内置文本框支持撤消,但我希望整个应用程序只有一个撤消堆栈)

有合理的方法吗？如果没有,是否有更好的方法来支持这样的撤消功能？

编辑:像下面的东西似乎工作 - 有什么更好的想法？(在这种情况下,我真的希望.NET有类似STL std::mismatch算法的东西......

    class TextModification
    {
        private string _OldValue;
        public string OldValue
        {
            get
            {
                return _OldValue;
            }
        }
        private string _NewValue;
        public string NewValue
        {
            get
            {
                return _NewValue;
            }
        }
        private int _Position;
        public int Position
        {
            get
            {
                return _Position;
            }
        }
        public TextModification(string oldValue, string newValue, int position)
        {
            _OldValue = oldValue;
            _NewValue = newValue;
            _Position = position;
        }
        public void RevertTextbox(System.Windows.Forms.TextBox tb)
        {
            tb.Text = tb.Text.Substring(0, Position) + OldValue + tb.Text.Substring(Position + NewValue.Length);
        }
    }

    private Stack<TextModification> changes = new Stack<TextModification>();
    private string OldTBText = "";
    private bool undoing = false;

    private void Undoit()
    {
        if (changes.Count == 0)
            return;
        undoing = true;
        changes.Pop().RevertTextbox(tbFilter);
        OldTBText = tbFilter.Text;
        undoing = false;
    }

    private void UpdateUndoStatus(TextBox caller)
    {
        int changeStartLocation = 0;
        int changeEndTBLocation = caller.Text.Length;
        int changeEndOldLocation = OldTBText.Length;
        while (changeStartLocation < Math.Min(changeEndOldLocation, changeEndTBLocation) &&
            caller.Text[changeStartLocation] == OldTBText[changeStartLocation])
            changeStartLocation++;
        while (changeEndTBLocation > 1 && changeEndOldLocation > 1 &&
            caller.Text[changeEndTBLocation-1] == OldTBText[changeEndOldLocation-1])
        {
            changeEndTBLocation--;
            changeEndOldLocation--;
        }
        changes.Push(new TextModification(
            OldTBText.Substring(changeStartLocation, changeEndOldLocation - changeStartLocation),
            caller.Text.Substring(changeStartLocation, changeEndTBLocation - changeStartLocation),
            changeStartLocation));
        OldTBText = caller.Text;
    }

    private void tbFilter_TextChanged(object sender, EventArgs e)
    {
        if (!undoing)
            UpdateUndoStatus((TextBox)sender);
    }

Answer 1

您可能最好使用Enter和Leave事件.输入时,将当前文本存储在类变量中,然后在离开时将新文本与旧文本进行比较.