你的帖子描述了你在代码中显示的定时器方案和内部循环中遇到的一些问题。但是你的实际目标是什么呢？你在帖子中说它的 * 存在理由 * 是：
[...]这样我就可以找到我用箭头键移动的图片框，并通过标签检查它是否与其他图片框冲突。
这"可能"被认为是X-Y Problem，因为可能有比定时器更优的方式来实现您最初想要做的事情（因为间隔为20ms的定时器可能会出现一些竞争条件，使其难以按预期启动和停止）。

• • 箭头键图片框**

考虑自定义PictureBox，当按下Left、Right、Up或Down时，它可以MoveProgrammatically(Keys direction)。它还需要根据IsCurrentMoveTarget属性跟踪这个"特定"图片框是否是应该移动的那个。当它"确实"成为当前移动目标时，它会通知所有"其他"示例它们不再是。

class ArrowKeyPictureBox : PictureBox
{
    public ArrowKeyPictureBox() 
    {
        LostFocus += (sender, e) =>Refresh();
        GotFocus += (sender, e) =>Refresh();
        MouseDown += (sender, e) =>
        {
            Focus();
            foreach (var control in Parent.Controls.OfType<ArrowKeyPictureBox>())
            {
                if (!ReferenceEquals(control, this)) control.IsCurrentMoveTarget = false;
            }
            IsCurrentMoveTarget = true;
        };
        Paint += (sender, e) =>
        {
            if (Focused && IsCurrentMoveTarget) using (var pen = new Pen(Color.Fuchsia))
                {
                    var rect = new Rectangle(
                        e.ClipRectangle.Location,
                        new Size(
                            (int)(e.ClipRectangle.Width - pen.Width),
                            (int)(e.ClipRectangle.Height - pen.Width)));
                    e.Graphics.DrawRectangle(pen, rect);
                }
        };
    }

Move方法具有碰撞检测功能，并在即将发生时激发一个可取消事件。

const int INCREMENT = 1;
    public void MoveProgrammatically(Keys direction)
    {
        Rectangle preview = Bounds;
        if (IsCurrentMoveTarget)
        {
            BringToFront();
            switch (direction)
            {
                case Keys.Up:
                    if (Top <= 0)
                    {
                        return;
                    }
                    preview.Y -= INCREMENT;
                    if(detectCollision())
                    {
                        return;
                    }
                    Top = preview.Y;
                    break;
                case Keys.Down:
                    if (Bottom >= Parent.Bottom)
                    {
                        return;
                    }
                    preview.Y += INCREMENT;
                    if (detectCollision())
                    {
                        return;
                    }
                    Top = preview.Y;
                    break;
                case Keys.Left:
                    if (Left <= 0)
                    {
                        return;
                    }
                    preview.X -= INCREMENT;
                    if (detectCollision())
                    {
                        return;
                    }
                    Left = preview.X;
                    break;
                case Keys.Right:
                    if (Right >= Parent.Right)
                    {
                        return;
                    }
                    preview.X += INCREMENT;
                    if (detectCollision())
                    {
                        return;
                    }
                    Left = preview.X;
                    break;
            }
        }
        bool detectCollision()
        {
            foreach (Control control in Parent.Controls)
            {
                if(!ReferenceEquals(this, control))
                {
                    if(preview.IntersectsWith(control.Bounds))
                    {
                        var e = new CollisionDetectedEventArgs(control: control);
                        CollisionDetected?.Invoke(this, e);
                        return !e.Cancel;
                    }
                }
            }
            return false;
        }
    }
    public static event CollisionDetectedEventHandler CollisionDetected;

确定这是否是要移动的控件，以及是否绘制聚焦框。

public bool IsCurrentMoveTarget
    {
        get => _isCurrentMoveTarget;
        set
        {
            if (!Equals(_isCurrentMoveTarget, value))
            {
                _isCurrentMoveTarget = value;
                Refresh();
            }
        }
    }
    bool _isCurrentMoveTarget = false;
}

• • 主窗体**

主窗体使用MessageFilter表示Up Down Left Right键事件，并将任何事件广播到它可能包含的所有ArrowKeyPictureBox示例。

public partial class MainForm : Form , IMessageFilter
{
    public MainForm()
    {
        InitializeComponent();
        Application.AddMessageFilter(this);
        Disposed += (sender, e) => Application.RemoveMessageFilter(this);
        ArrowKeyPictureBox.CollisionDetected += onAnyCollisionDetected;
    }

    const int WM_KEYDOWN = 0x0100;
    public bool PreFilterMessage(ref Message m)
    {
        switch (m.Msg)
        {
            case WM_KEYDOWN:
                if (Controls.OfType<ArrowKeyPictureBox>().Any(_ => _.Focused))
                {
                    Keys key = (Keys)m.WParam;
                    switch (key)
                    {
                        case Keys.Up:
                        case Keys.Down:
                        case Keys.Left:
                        case Keys.Right:
                            BeginInvoke(new Action(() =>
                            {
                                foreach (var target in Controls.OfType<ArrowKeyPictureBox>())
                                {
                                    target.MoveProgrammatically(key);
                                }
                            }));
                            // Suppress OS tabbing to prevent loss of focus.
                            return true;
                    }
                }
                break;
        }
        return false;
    }

显示碰撞状态：

private void onAnyCollisionDetected(object sender, CollisionDetectedEventArgs e)
    {
        e.Cancel = !e.Control.Name.Contains("Portal");
        if (sender is Control control)
        {
            if (!_prevWarning.Equals(control.Bounds))
            {
                richTextBox.SelectionFont = new Font(richTextBox.Font, FontStyle.Bold);
                richTextBox.SelectionColor = e.Cancel ? Color.Green : Color.Red;
                richTextBox.AppendText($"{Environment.NewLine}Collision{Environment.NewLine}");
                richTextBox.SelectionFont = new Font(richTextBox.Font, FontStyle.Regular);
                richTextBox.SelectionColor = Color.Black;

                List<string> builder = new List<string>();
                builder.Add($"Moving: {control.Name}");
                builder.Add($"@ {control.Bounds}");
                builder.Add($"Collided with: {e.Control.Name}");
                builder.Add($"@ {e.Control.Bounds}");
                richTextBox.AppendText($"{string.Join(Environment.NewLine, builder)}{Environment.NewLine}");
                richTextBox.ScrollToCaret();
                _prevWarning = control.Bounds;
            }
        }
    }
    Rectangle _prevWarning = new Rectangle();
}