C# 调用 API

C# 中使用 API 接口的方法如下:

// 导入 System.Runtime.InteropServices 名称空间

using System.Runtime.InteropServices;

// 声明所要用到的API函数

[DllImport("kernel32")]
public static extern void GetWindowsDirectory(System.Text.StringBuilder WinDir,int count);

[DllImport("kernel32")]
public static extern void GetSystemDirectory(StringBuilder SysDir,int count);

[DllImport("kernel32")]
public static extern void GetSystemInfo(ref CPU_INFO cpuinfo);

[DllImport("kernel32")]
public static extern void GlobalMemoryStatus(ref MEMORY_INFO meminfo);

[DllImport("kernel32")]
public static extern void GetSystemTime(ref SYSTEMTIME_INFO stinfo);

//定义以下各结构
//定义CPU的信息结构
[StructLayout(LayoutKind.Sequential)]
public struct CPU_INFO
{
public uint dwOemId;
public uint dwPageSize;
public uint lpMinimumApplicationAddress;
public uint lpMaximumApplicationAddress;
public uint dwActiveProcessorMask;
public uint dwNumberOfProcessors;
public uint dwProcessorType;
public uint dwAllocationGranularity;
public uint dwProcessorLevel;
public uint dwProcessorRevision;
}

//定义内存的信息结构
[StructLayout(LayoutKind.Sequential)]
public struct MEMORY_INFO
{
public uint dwLength;
public uint dwMemoryLoad;
public uint dwTotalPhys;
public uint dwAvailPhys;
public uint dwTotalPageFile;
public uint dwAvailPageFile;
public uint dwTotalVirtual;
public uint dwAvailVirtual;
}

//定义系统时间的信息结构
[StructLayout(LayoutKind.Sequential)]
public struct SYSTEMTIME_INFO
{
public ushort wYear;
public ushort wMonth;
public ushort wDayOfWeek;
public ushort wDay;
public ushort wHour;
public ushort wMinute;
public ushort wSecond;
public ushort wMilliseconds;
}
//调用GetWindowsDirectory和GetSystemDirectory函数分别取得Windows路径和系统路径
const int nChars = 128;
StringBuilder Buff = new StringBuilder(nChars);
GetWindowsDirectory(Buff,nChars);
WindowsDirectory.Text = "Windows路径:"+Buff.ToString();
GetSystemDirectory(Buff,nChars);
SystemDirectory.Text = "系统路径:"+Buff.ToString();

//调用GetSystemInfo函数获取CPU的相关信息
CPU_INFO CpuInfo;
CpuInfo = new CPU_INFO();
GetSystemInfo(ref CpuInfo);
NumberOfProcessors.Text = "本计算机中有"+CpuInfo.dwNumberOfProcessors.ToString()+"个CPU";
ProcessorType.Text = "CPU的类型为"+CpuInfo.dwProcessorType.ToString();
ProcessorLevel.Text = "CPU等级为"+CpuInfo.dwProcessorLevel.ToString();
OemId.Text = "CPU的OEM ID为"+CpuInfo.dwOemId.ToString();
PageSize.Text = "CPU中的页面大小为"+CpuInfo.dwPageSize.ToString();

//调用GlobalMemoryStatus函数获取内存的相关信息
MEMORY_INFO MemInfo;
MemInfo = new MEMORY_INFO();
GlobalMemoryStatus(ref MemInfo);
MemoryLoad.Text = MemInfo.dwMemoryLoad.ToString()+"%的内存正在使用";
TotalPhys.Text = "物理内存共有"+MemInfo.dwTotalPhys.ToString()+"字节";
AvailPhys.Text = "可使用的物理内存有"+MemInfo.dwAvailPhys.ToString()+"字节";
TotalPageFile.Text = "交换文件总大小为"+MemInfo.dwTotalPageFile.ToString()+"字节";
AvailPageFile.Text = "尚可交换文件大小为"+MemInfo.dwAvailPageFile.ToString()+"字节";
TotalVirtual.Text = "总虚拟内存有"+MemInfo.dwTotalVirtual.ToString()+"字节";
AvailVirtual.Text = "未用虚拟内存有"+MemInfo.dwAvailVirtual.ToString()+"字节";

//调用GetSystemTime函数获取系统时间信息
SYSTEMTIME_INFO StInfo;
StInfo = new SYSTEMTIME_INFO();
GetSystemTime(ref StInfo);
Date.Text = StInfo.wYear.ToString()+"年"+StInfo.wMonth.ToString()+"月"+StInfo.wDay.ToString()+"日";
Time.Text = (StInfo.wHour+8).ToString()+"点"+StInfo.wMinute.ToString()+"分"+StInfo.wSecond.ToString()+"秒";

修饰符

关键词 意义
DllImport 指定 DLL 的位置
LayoutKind.Automatic 为了提高效率允许运行态对类型成员重新排序
LayoutKind.Explicit 对每个域按照FieldOffset属性对类型成员排序
LayoutKind.Sequential 对出现在受管辖类型定义地方的不受管辖内存中的类型成员进行排序