C#啓動一個外部程序(3)-CreateProcess

今天還是繼續說說C#調用系統Api啓動外部程序的方法，今天要說的是CreateProcess這個Api函數，相比前兩篇文章(一、二)中所說的Api，CreateProcess參數要更復雜一些，但使用起來，要更靈活。
1.

using System.Runtime.InteropServices;

2. CreateProcess中用到了幾個結構體類型，先聲明他們：

        [System.Runtime.InteropServices.StructLayout(LayoutKind.Sequential)]
        public class SECURITY_ATTRIBUTES
        {
            public int nLength;
            public string lpSecurityDescriptor;
            public bool bInheritHandle;
        }

        [StructLayout(LayoutKind.Sequential)]
        public struct STARTUPINFO
        {
            public int cb;
            public string lpReserved;
            public string lpDesktop;
            public int lpTitle;
            public int dwX;
            public int dwY;
            public int dwXSize;
            public int dwYSize;
            public int dwXCountChars;
            public int dwYCountChars;
            public int dwFillAttribute;
            public int dwFlags;
            public int wShowWindow;
            public int cbReserved2;
            public byte lpReserved2;
            public IntPtr hStdInput;
            public IntPtr hStdOutput;
            public IntPtr hStdError;
        }

        [StructLayout(LayoutKind.Sequential)]
        public struct PROCESS_INFORMATION
        {
            public IntPtr hProcess;
            public IntPtr hThread;
            public int dwProcessId;
            public int dwThreadId;
        }

3. 聲明CreateProcess

        [DllImport("Kernel32.dll", CharSet = CharSet.Ansi)]
        public static extern bool CreateProcess(
            StringBuilder lpApplicationName, StringBuilder lpCommandLine,
            SECURITY_ATTRIBUTES lpProcessAttributes,
            SECURITY_ATTRIBUTES lpThreadAttributes,
            bool bInheritHandles,
            int dwCreationFlags,
            StringBuilder lpEnvironment,
            StringBuilder lpCurrentDirectory,
            ref STARTUPINFO lpStartupInfo,
            ref PROCESS_INFORMATION lpProcessInformation
            );

4. 下邊這三個也是Api，作用看註釋

        #region Win32 Api : WaitForSingleObject
        //檢測一個系統核心對象(線程，事件，信號)的信號狀態，當對象執行時間超過dwMilliseconds就返回，否則就一直等待對象返回信號
        [DllImport("Kernel32.dll")]
        public static extern uint WaitForSingleObject(System.IntPtr hHandle, uint dwMilliseconds);

        #endregion

        #region Win32 Api : CloseHandle
        //關閉一個內核對象,釋放對象佔有的系統資源。其中包括文件、文件映射、進程、線程、安全和同步對象等
        [DllImport("Kernel32.dll")]
        public static extern bool CloseHandle(System.IntPtr hObject);

        #endregion       

        #region Win32 Api : GetExitCodeProcess
        //獲取一個已中斷進程的退出代碼,非零表示成功，零表示失敗。
        //參數hProcess，想獲取退出代碼的一個進程的句柄，參數lpExitCode，用於裝載進程退出代碼的一個長整數變量。
        [DllImport("Kernel32.dll")]
        static extern bool GetExitCodeProcess(System.IntPtr hProcess, ref uint lpExitCode);

        #endregion

5. 如果示例中argm指定的程序執行時間很長，進程會被阻塞到WaitForSingleObject行處，直到命令執行完畢或進程被中止才繼續執行後邊的語句。

            string argm = "cmd.exe";

            STARTUPINFO sInfo = new STARTUPINFO();
            PROCESS_INFORMATION pInfo = new PROCESS_INFORMATION();

            if (!CreateProcess(null, new StringBuilder(argm), null, null, false, 0, null, null, ref sInfo, ref pInfo))
            {
                throw new Exception("調用失敗");
            }
            uint i = 0;
            WaitForSingleObject(pInfo.hProcess, int.MaxValue);            
            GetExitCodeProcess(pInfo.hProcess, ref i);
            CloseHandle(pInfo.hProcess);
            CloseHandle(pInfo.hThread);