winform DataGridView重绘滚动条样式

要重绘WinForm DataGridView的滚动条样式，需要继承DataGridView并重写它的WndProc方法。以下是一个示例代码，可以实现自定义滚动条样式：

using System;
using System.Drawing;
using System.Runtime.InteropServices;
using System.Windows.Forms;

public class CustomDataGridView : DataGridView
{
    private const int WM_PAINT = 0xF;
    private const int WM_NCPAINT = 0x85;
    private const int WM_NCCALCSIZE = 0x83;
    private const int WM_ERASEBKGND = 0x14;

    private bool isScrolling = false;

    protected override void WndProc(ref Message m)
    {
        switch (m.Msg)
        {
            case WM_PAINT:
                base.WndProc(ref m);
                DrawScrollBar();
                break;
            case WM_NCPAINT:
            case WM_NCCALCSIZE:
            case WM_ERASEBKGND:
                break;
            default:
                base.WndProc(ref m);
                break;
        }
    }

    private void DrawScrollBar()
    {
        if (!isScrolling)
        {
            // 获取滚动条的Graphics对象
            Graphics g = this.CreateGraphics();

            // 绘制滚动条背景
            Rectangle bgRect = new Rectangle(this.VerticalScrollingOffset + this.Width - SystemInformation.VerticalScrollBarWidth, this.ColumnHeadersHeight, SystemInformation.VerticalScrollBarWidth, this.Height - this.ColumnHeadersHeight);
            g.FillRectangle(new SolidBrush(this.BackgroundColor), bgRect);

            // 绘制滚动条轨道
            Rectangle trackRect = new Rectangle(bgRect.X + 1, bgRect.Y + SystemInformation.VerticalScrollBarArrowHeight, bgRect.Width - 2, bgRect.Height - 2 * SystemInformation.VerticalScrollBarArrowHeight);
            ControlPaint.DrawScrollTrack(g, trackRect, ScrollOrientation.Vertical);

            // 绘制滚动条滑块
            Rectangle thumbRect = new Rectangle(bgRect.X + 1, bgRect.Y + SystemInformation.VerticalScrollBarArrowHeight + (this.FirstDisplayedScrollingRowIndex * trackRect.Height / this.RowCount), bgRect.Width - 2, this.DisplayedRowCount(false) * trackRect.Height / this.RowCount);
            ControlPaint.DrawScrollThumb(g, thumbRect, ScrollState.Focused);

            // 释放Graphics对象
            g.Dispose();
        }
    }

    protected override void OnScroll(ScrollEventArgs e)
    {
        isScrolling = true;
        base.OnScroll(e);
        isScrolling = false;
        this.Invalidate(new Rectangle(this.Width - SystemInformation.VerticalScrollBarWidth, this.ColumnHeadersHeight, SystemInformation.VerticalScrollBarWidth, this.Height - this.ColumnHeadersHeight()));
    }
}

在上述代码中，我们首先重写了DataGridView的WndProc方法，在其中处理WM_PAINT消息并调用DrawScrollBar方法绘制滚动条。DrawScrollBar方法中，我们使用CreateGraphics方法获取滚动条的Graphics对象，然后绘制滚动条背景、轨道和滑块。最后，记得在OnScroll方法中调用Invalidate方法重新绘制滚动条。

使用上述代码，我们可以实现自定义滚动条样式。需要注意的是，由于我们使用了CreateGraphics方法获取Graphics对象，因此需要在绘制完滚动条后释放该对象。此外，在绘制滑块时，我们使用了FirstDisplayedScrollingRowIndex和DisplayedRowCount方法来获取当前滚动条位置和可见行数，因此需要确保这些属性已经被正确设置。