C#中使用User32.dll的常见用法示例

**使用 User32.dll 的 C# 示例**

`User32.dll` 是 Windows API 中的一个重要库，提供了许多用于操作系统交互的函数。C# 程序员可以通过 P/Invoke（Platform Invoke）技术在 C# 中调用这些函数。下面是一些常见用法示例。

###1. 获取当前窗口句柄`GetForegroundWindow()` 函数返回当前激活的窗口的句柄。

csharpusing System;
using System.Runtime.InteropServices;

class Program{
 [DllImport("User32.dll")]
 static extern IntPtr GetForegroundWindow();

 static void Main()
 {
 IntPtr hwnd = GetForegroundWindow();
 Console.WriteLine(hwnd);
 }
}

csharpusing System;
using System.Runtime.InteropServices;

class Program{
 [DllImport("User32.dll")]
 static extern bool GetWindowText(IntPtr hwnd, StringBuilder lpString, int nMaxCount);

 static void Main()
 {
 IntPtr hwnd = GetForegroundWindow();
 StringBuilder sb = new StringBuilder(256);
 if (GetWindowText(hwnd, sb,256))
 {
 Console.WriteLine(sb.ToString());
 }
 }
}

csharpusing System;
using System.Runtime.InteropServices;

class Program{
 [DllImport("User32.dll")]
 static extern bool GetWindowRect(IntPtr hwnd, out RECT lpRect);

 [StructLayout(LayoutKind.Sequential)]
 public struct RECT {
 public int Left;
 public int Top;
 public int Right;
 public int Bottom;
 }

 static void Main()
 {
 IntPtr hwnd = GetForegroundWindow();
 RECT rect;
 if (GetWindowRect(hwnd, out rect))
 {
 Console.WriteLine($"Width: {rect.Right - rect.Left}, Height: {rect.Bottom - rect.Top}");
 }
 }
}

csharpusing System;
using System.Runtime.InteropServices;

class Program{
 [DllImport("User32.dll")]
 static extern IntPtr CreateWindowEx(
 uint dwExStyle,
 string lpClassName,
 string lpWindowName,
 uint style,
 int x,
 int y,
 int nWidth,
 int nHeight,
 IntPtr hWndParent,
 IntPtr hMenu,
 IntPtr hInstance,
 IntPtr lpParam );

 static void Main()
 {
 IntPtr hwnd = CreateWindowEx(
0, // dwExStyle "STATIC", // lpClassName "Hello, World!", // lpWindowName0x00000000, // style100, // x100, // y200, // nWidth50, // nHeight IntPtr.Zero, // hWndParent IntPtr.Zero, // hMenu Marshal.GetHINSTANCE(typeof(Program)), // hInstance IntPtr.Zero // lpParam );
 Console.WriteLine(hwnd);
 }
}

csharpusing System;
using System.Runtime.InteropServices;

class Program{
 [DllImport("User32.dll")]
 static extern bool ShowWindow(IntPtr hwnd, int nCmdShow);

 static void Main()
 {
 IntPtr hwnd = GetForegroundWindow();
 ShowWindow(hwnd,9); // SW_SHOW }
}