前些天对WMI的铺垫，今天开始编程部分，转载继续...
WMI(Windows Management Instrumentation)是Windows下可以与系统信息(包括软硬件等)的一个管理框架，通过WMI可以很方便地对机器进行管理。现在以通过WMI来打开(或创建)一个记事本(notepad.exe)进程为例，看看VC++到.Net的变迁，一览.Net是如何让程序员从繁琐晦涩的程序中解放出来。
1、预工作：
VC++中需要在源代码中加入：
#include <Wbemidl.h>
#pragma comment(lib, "wbemuuid.lib")
VC#中需要：
在工程中添加引用：System.Management
在代码中加入using System.Management;
2、流程：
VC++的代码，需要6步和查询返回值、最后释放资源：
// Step 1: --------------------------------------------------
// Initialize COM. ------------------------------------------
hres = CoInitializeEx(0, COINIT_MULTITHREADED);
// Step 2: --------------------------------------------------
// Set general COM security levels --------------------------
hres = CoInitializeSecurity(
NULL,
-1, // COM negotiates service
NULL, // Authentication services
NULL, // Reserved
RPC_C_AUTHN_LEVEL_DEFAULT, // Default authentication
RPC_C_IMP_LEVEL_IMPERSONATE, // Default Impersonation
NULL, // Authentication info
EOAC_NONE, // Additional capabilities
NULL // Reserved
);
// Step 3: ---------------------------------------------------
// Obtain the initial locator to WMI -------------------------
IWbemLocator *pLoc = NULL;
hres = CoCreateInstance(
CLSID_WbemLocator,
0,
CLSCTX_INPROC_SERVER,
IID_IWbemLocator, (LPVOID *) &pLoc);
// Step 4: ---------------------------------------------------
// Connect to WMI through the IWbemLocator::ConnectServer method
IWbemServices *pSvc = NULL;
// Connect to the local root\cimv2 namespace
// and obtain pointer pSvc to make IWbemServices calls.
hres = pLoc->ConnectServer(
_bstr_t(L"ROOT\\CIMV2"),
NULL,
NULL,
0,
NULL,
0,
0,
&pSvc
);
// Step 5: --------------------------------------------------
// Set security levels for the proxy ------------------------
hres = CoSetProxyBlanket(
pSvc, // Indicates the proxy to set
RPC_C_AUTHN_WINNT, // RPC_C_AUTHN_xxx
RPC_C_AUTHZ_NONE, // RPC_C_AUTHZ_xxx
NULL, // Server principal name
RPC_C_AUTHN_LEVEL_CALL, // RPC_C_AUTHN_LEVEL_xxx
RPC_C_IMP_LEVEL_IMPERSONATE, // RPC_C_IMP_LEVEL_xxx
NULL, // client identity
EOAC_NONE // proxy capabilities
);
// Step 6: --------------------------------------------------
// Use the IWbemServices pointer to make requests of WMI ----
// set up to call the Win32_Process::Create method
BSTR MethodName = SysAllocString(L"Create");
BSTR ClassName = SysAllocString(L"Win32_Process");
IWbemClassObject* pClass = NULL;
hres = pSvc->GetObject(ClassName, 0, NULL, &pClass, NULL);
IWbemClassObject* pInParamsDefinition = NULL;
hres = pClass->GetMethod(MethodName, 0,
&pInParamsDefinition, NULL);
IWbemClassObject* pClassInstance = NULL;
hres = pInParamsDefinition->SpawnInstance(0, &pClassInstance);
// Create the values for the in parameters
VARIANT varCommand;
varCommand.vt = VT_BSTR;
varCommand.bstrVal = L"notepad.exe";
// Store the value for the in parameters
hres = pClassInstance->Put(L"CommandLine", 0,
&varCommand, 0);
wprintf(L"The command is: %s\n", V_BSTR(&varCommand));
// Execute Method
IWbemClassObject* pOutParams = NULL;
hres = pSvc->ExecMethod(ClassName, MethodName, 0, NULL, pClassInstance, &pOutParams, NULL);
// Get return value
VARIANT varReturnValue;
hres = pOutParams->Get(_bstr_t(L"ReturnValue"), 0, &varReturnValue, NULL, 0);
// Last: clean up
VariantClear(&varCommand);
VariantClear(&varReturnValue);
SysFreeString(ClassName);
SysFreeString(MethodName);
pClass->Release();
pInParamsDefinition->Release();
pOutParams->Release();
pLoc->Release();
pSvc->Release();
CoUninitialize();
VC#只需寥寥数行就可以实现（暂不考虑错误处理）：
跳过VC++中的Step1~5，直接从Step6开始。而且非常直观：
ManagementClass mc = new ManagementClass("Win32_Process");
ManagementBaseObject obj = mc.GetMethodParameters("Create");
obj["CommandLine"]="notepad.exe";
mc.InvokeMethod("Create", obj, null);
mc.Dispose();
.Net对WMI良好的封装，还有对字符串的更强支持、方便的垃圾回收机制，使程序既一目了然，又易于维护。其实类似的区别在VC vs VB年代已经出现了（特别是在COM组件编写和调用方面可以看出），从这点也可以看出.Net完全继承了VB易学易用的特性，又不失强大的功能。
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