快速加载背景图片（解决大量控件时闪烁）

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
        PanelEnhanced panelEnhanced = new PanelEnhanced();
        this.Controls.Add(panelEnhanced);
        panelEnhanced.Dock = DockStyle.Fill;
        panelEnhanced.BackgroundImage = Image.FromFile(@"D:\pic\b.jpg");
    }
}

class PanelEnhanced : Panel
{
    protected override void OnPaintBackground(PaintEventArgs e)
    {
        return;
    }

    protected override void OnPaint(PaintEventArgs e)
    {
        this.DoubleBuffered = true;
        if (this.BackgroundImage != null)
        {
            e.Graphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
            e.Graphics.DrawImage(
                this.BackgroundImage,
                new System.Drawing.Rectangle(0, 0, this.Width, this.Height),
                0,
                0,
                this.BackgroundImage.Width,
                this.BackgroundImage.Height,
                System.Drawing.GraphicsUnit.Pixel);
        }
        base.OnPaint(e);
    }
}