WinForm中无法修改TabControl顶部区域颜色的解决办法求助

WinForm原生TabControl的顶部未被标签覆盖的区域属于系统绘制的非客户区，常规属性无法修改，以下是两种可行的解决方法：

方法一：自定义自绘TabControl #

通过继承TabControl并开启自绘模式，手动绘制标签和顶部背景区域，完全控制外观：

public class CustomTabControl : TabControl
{
    public CustomTabControl()
    {
        DrawMode = TabDrawMode.OwnerDrawFixed;
        SizeMode = TabSizeMode.Fixed;
        ItemSize = new Size(100, 25); // 可根据需求调整标签尺寸
    }

    protected override void OnPaint(PaintEventArgs e)
    {
        base.OnPaint(e);
        var parentBackColor = Parent?.BackColor ?? BackColor;
        
        // 绘制顶部未被标签覆盖的空白区域
        using var bgBrush = new SolidBrush(parentBackColor);
        int startX = TabCount > 0 ? GetTabRect(TabCount - 1).Right : 0;
        e.Graphics.FillRectangle(bgBrush, startX, 0, Width - startX, ItemSize.Height);
        if (TabCount == 0)
        {
            e.Graphics.FillRectangle(bgBrush, 0, 0, Width, ItemSize.Height);
        }

        // 逐个绘制标签
        for (int i = 0; i < TabCount; i++)
        {
            var tabRect = GetTabRect(i);
            // 标签背景色：选中标签用控件主体背景色，未选中用父容器（Form）背景色
            using var tabBrush = new SolidBrush(SelectedIndex == i ? BackColor : parentBackColor);
            e.Graphics.FillRectangle(tabBrush, tabRect);
            
            // 绘制标签文本
            TextRenderer.DrawText(e.Graphics, TabPages[i].Text, Font, tabRect, ForeColor, 
                TextFormatFlags.HorizontalCenter | TextFormatFlags.VerticalCenter);
            
            // 可选：绘制标签边框
            using var borderPen = new Pen(Color.Gray);
            e.Graphics.DrawRectangle(borderPen, tabRect);
        }
    }

    protected override void OnPaintBackground(PaintEventArgs pevent)
    {
        // 填充控件主体背景
        using var bgBrush = new SolidBrush(BackColor);
        pevent.Graphics.FillRectangle(bgBrush, ClientRectangle);
        
        // 填充顶部标签栏整体背景
        var parentBackColor = Parent?.BackColor ?? BackColor;
        using var topBrush = new SolidBrush(parentBackColor);
        pevent.Graphics.FillRectangle(topBrush, 0, 0, Width, ItemSize.Height);
    }
}

方法二：通过Win32消息修改非客户区 #

直接拦截WM_NCPAINT消息，手动绘制顶部非客户区背景：

public class CustomTabControl : TabControl
{
    private const int WM_NCPAINT = 0x85;

    protected override void WndProc(ref Message m)
    {
        base.WndProc(ref m);
        if (m.Msg == WM_NCPAINT)
        {
            var hdc = GetWindowDC(Handle);
            if (hdc != IntPtr.Zero)
            {
                using var g = Graphics.FromHdc(hdc);
                var parentBackColor = Parent?.BackColor ?? BackColor;
                using var brush = new SolidBrush(parentBackColor);
                // 绘制顶部非客户区矩形
                g.FillRectangle(brush, 0, 0, Width, ItemSize.Height);
                
                ReleaseDC(Handle, hdc);
            }
        }
    }

    [System.Runtime.InteropServices.DllImport("user32.dll")]
    private static extern IntPtr GetWindowDC(IntPtr hWnd);

    [System.Runtime.InteropServices.DllImport("user32.dll")]
    private static extern int ReleaseDC(IntPtr hWnd, IntPtr hDC);
}

使用说明 #

1. 将上述代码添加到你的项目中
2. 在Form设计器里，删除原有的TabControl，将CustomTabControl拖到Form上（或通过代码实例化）
3. 确保Form的BackColor设置为你需要的灰色，自定义控件会自动匹配该颜色

内容的提问来源于stack exchange，提问作者QuickSilvain