C#winform置顶不聚焦

在C# WinForms中，要实现窗体置顶但不聚焦的效果，可以使用以下代码：

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

public partial class Form1 : Form
{
    // 导入SetWindowPos函数
    [DllImport("user32.dll")]
    private static extern bool SetWindowPos(IntPtr hWnd, IntPtr hWndInsertAfter, int X, int Y, int cx, int cy, uint uFlags);

    // 定义常量
    private const uint SWP_NOSIZE = 0x0001;
    private const uint SWP_NOMOVE = 0x0002;
    private const uint SWP_NOACTIVATE = 0x0010;
    private static readonly IntPtr HWND_TOPMOST = new IntPtr(-1);

    public Form1()
    {
        InitializeComponent();
    }

    protected override bool ShowWithoutActivation
    {
        get { return true; }
    }

    protected override CreateParams CreateParams
    {
        get
        {
            CreateParams createParams = base.CreateParams;
            createParams.ExStyle |= 0x08000000; // WS_EX_NOACTIVATE
            return createParams;
        }
    }

    protected override void OnLoad(EventArgs e)
    {
        base.OnLoad(e);
        
        // 窗体加载时设置置顶
        SetTopMost(this.Handle);
    }

    private void SetTopMost(IntPtr handle)
    {
        SetWindowPos(handle, HWND_TOPMOST, 0, 0, 0, 0, SWP_NOSIZE | SWP_NOMOVE | SWP_NOACTIVATE);
    }
}

这段代码中，通过调用`SetWindowPos`函数，将窗体设置为置顶且不聚焦。在窗体加载时调用`SetTopMost`函数即可实现。