在C#中，要修改ContextMenuStrip的樣式，您可以通過自定義屬性來實現。以下是一些常見的方法來更改ContextMenuStrip的樣式：

1. 修改背景顏色和前景顏色：

contextMenuStrip1.BackColor = Color.LightGray;
contextMenuStrip1.ForeColor = Color.Black;

2. 修改字體樣式：

contextMenuStrip1.Font = new Font("Arial", 10, FontStyle.Bold);

3. 修改邊框樣式：

contextMenuStrip1.BorderStyle = BorderStyle.FixedSingle;

4. 修改圓角半徑：

contextMenuStrip1.RoundedEdges = true;
contextMenuStrip1.Radius = 5;

5. 添加自定義背景圖像：

contextMenuStrip1.Renderer = new CustomContextMenuStripRenderer();
contextMenuStrip1.Renderer.DrawBackground += new EventHandler(contextMenuStrip1_Renderer_DrawBackground);

private void contextMenuStrip1_Renderer_DrawBackground(object sender, EventArgs e)
{
    var contextMenuStrip = sender as ContextMenuStrip;
    if (contextMenuStrip != null)
    {
        using (Graphics g = contextMenuStrip.CreateGraphics())
        {
            // 繪制背景圖像
            using (Image backgroundImage = Image.FromFile("path/to/your/image.png"))
            {
                g.DrawImage(backgroundImage, new Point(0, 0));
            }
        }
    }
}

6. 添加自定義分隔線樣式：

contextMenuStrip1.Renderer = new CustomContextMenuStripRenderer();
contextMenuStrip1.Renderer.DrawSeparator += new EventHandler(contextMenuStrip1_Renderer_DrawSeparator);

private void contextMenuStrip1_Renderer_DrawSeparator(object sender, EventArgs e)
{
    var contextMenuStrip = sender as ContextMenuStrip;
    if (contextMenuStrip != null)
    {
        using (Graphics g = contextMenuStrip.CreateGraphics())
        {
            // 繪制分隔線
            ControlPaint.DrawBorderLine(g, contextMenuStrip.ClientRectangle, Color.Black, ButtonBorderStyle.Solid);
        }
    }
}

通過這些方法，您可以自定義ContextMenuStrip的樣式以滿足您的需求。請注意，您需要將CustomContextMenuStripRenderer替換為您自己的渲染器類，以實現自定義繪制。