在pictureBox画矩形可用mouse调节大小、拖动位置

好的，您可以通过以下代码实现该功能：

public partial class Form1 : Form
{
    private bool isMouseDown = false;
    private Point mouseDownPos;
    private Rectangle rectangle = new Rectangle(50, 50, 100, 100);

    public Form1()
    {
        InitializeComponent();

        pictureBox1.MouseDown += pictureBox1_MouseDown;
        pictureBox1.MouseMove += pictureBox1_MouseMove;
        pictureBox1.MouseUp += pictureBox1_MouseUp;
        pictureBox1.Paint += pictureBox1_Paint;
    }

    private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
    {
        if (e.Button == MouseButtons.Left)
        {
            isMouseDown = true;
            mouseDownPos = e.Location;
        }
    }

    private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
    {
        if (isMouseDown)
        {
            int width = e.X - mouseDownPos.X;
            int height = e.Y - mouseDownPos.Y;
            rectangle = new Rectangle(mouseDownPos.X, mouseDownPos.Y, width, height);
            pictureBox1.Invalidate();
        }
    }

    private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
    {
        if (e.Button == MouseButtons.Left)
        {
            isMouseDown = false;
        }
    }

    private void pictureBox1_Paint(object sender, PaintEventArgs e)
    {
        e.Graphics.DrawRectangle(Pens.Red, rectangle);
    }
}

在上述代码中，我们通过 `pictureBox1` 控件的 `MouseDown`、`MouseMove` 和 `MouseUp` 事件来实现鼠标的拖动功能，同时通过 `pictureBox1` 控件的 `Paint` 事件在控件上绘制矩形。其中， `isMouseDown` 变量用于判断鼠标是否按下， `mouseDownPos` 变量用于记录鼠标按下的位置， `rectangle` 变量用于存储矩形的位置和大小信息。您可以根据需要修改矩形的初始位置和大小。