我正在尝试在新类中使用dll导入，但是在此声明类型上出现错误属性'DllImport'无效

Question

The error Attribute 'DllImport' is not valid on this declaration type. It is only valid on 'method' declarations. Tried to add the dll import before the class in a method but same error.

using System;
using System.Collections.Generic;
using System.Text;
using System.Management;
using System.Diagnostics;
using System.Runtime.InteropServices;

namespace MinimizeCapture
{

    class WatchForWindow
    {
        [DllImport("user32.dll")]
        private const int SW_SHOWNORMAL = 1;
        private const int SW_SHOWMINIMIZED = 2;
        private const int SW_SHOWMAXIMIZED = 3;

        private static ManagementEventWatcher watcher = null;

        public static void StartWatching()
        {
            WqlEventQuery query = new WqlEventQuery("Select * From __InstanceCreationEvent Within 2 Where TargetInstance Isa 'Win32_Process'");
            watcher = new ManagementEventWatcher(query);
            watcher.EventArrived += new EventArrivedEventHandler(watcher_EventArrived);
            watcher.Start();
        }

        public static void StopWatching()
        {
            if (watcher != null)
            {
                watcher.Stop();
            }
        }

        private static void watcher_EventArrived(object sender, EventArrivedEventArgs e)
        {
            ManagementBaseObject obj = (ManagementBaseObject)e.NewEvent["TargetInstance"];
            string t = obj["Name"].ToString();
            GetHWND(t);
        }

        private static void GetHWND(string wName)
        {
            IntPtr hWnd = FindWindow("Notepad", "Untitled - Notepad");

        }
    }
}

The error is on this line:

[DllImport("user32.dll")]

I'm trying to use it since FindWindow is not exist.

Answer 1

You must apply the [DllImport] attribute on a method declaration without a body, bearing the static extern modifiers.

You can look up translated function declarations on PInvoke.net , including relevant structures when required. The function FindWindow , which you require, looks like this:

[DllImport("user32.dll", SetLastError = true)]
static extern IntPtr FindWindow(string lpClassName, string lpWindowName);