Code Snippet: Restrict to your application to one instance.

   简单来说，这段代码调用 Win32API CreateEvent Function 创建一个全局的Event 对象。

如果这个对象已经存在，GetLastError 会返回 183  ERROR_ALREADY_EXISTS。

个人意见以为这个方法比满世界地找Handle 用起来舒服。

            SECURITY_ATTRIBUTES attributes = new SECURITY_ATTRIBUTES();
            SECURITY_DESCRIPTOR descriptor = new SECURITY_DESCRIPTOR();
        
            IntPtr sharedFile = IntPtr.Zero;
            IntPtr pDescriptor = IntPtr.Zero;
            IntPtr pAttributes = IntPtr.Zero;
            try
            ...{
                pDescriptor = Marshal.AllocHGlobal(Marshal.SizeOf(descriptor));
                pAttributes = Marshal.AllocHGlobal(Marshal.SizeOf(attributes));

                attributes.nLength = Marshal.SizeOf(attributes);
                attributes.bInheritHandle = true;
                attributes.lpSecurityDescriptor = pDescriptor;

                if (!InterOp.InitializeSecurityDescriptor(ref descriptor, 1 /**//*SECURITY_DESCRIPTOR_REVISION*/))
                    throw new ApplicationException("InitializeSecurityDescriptor failed: " + Marshal.GetLastWin32Error());

                if (!InterOp.SetSecurityDescriptorDacl(ref descriptor, true, IntPtr.Zero, false))
                    throw new ApplicationException("SetSecurityDescriptorDacl failed: " + Marshal.GetLastWin32Error());

                Marshal.StructureToPtr(descriptor, pDescriptor, false);
                Marshal.StructureToPtr(attributes, pAttributes, false);

                bufferEvent = InterOp.CreateEvent(pAttributes, false, false, "Your Name Here");

                if (bufferEvent == IntPtr.Zero) 
                    throw new ApplicationException("CreateEvent (bufferEvent) failed: " + Marshal.GetLastWin32Error());

                if (Marshal.GetLastWin32Error() == 183 /**//*ERROR_ALREADY_EXISTS*/)
                    // Another instance is running, add your code here.
            }
            finally
            ...{
                Marshal.FreeHGlobal(pDescriptor);
                Marshal.FreeHGlobal(pAttributes);
            }
 
上面代码用到的几个Win32 Function/结构的定义：
    internal abstract class InterOp
    ...{
        [DllImport("advapi32.dll", SetLastError=true)]
        internal static extern bool InitializeSecurityDescriptor([In] ref SECURITY_DESCRIPTOR pSecurityDescriptor, int dwRevision);

        [DllImport("advapi32.dll", SetLastError=true)]
        internal static extern bool SetSecurityDescriptorDacl
              ([In] ref SECURITY_DESCRIPTOR pSecurityDescriptor,
               bool bDaclPresent,
               IntPtr pDacl, 
               bool bDaclDefaulted);

        [DllImport("kernel32.dll", SetLastError=true, CharSet=CharSet.Auto)]
        internal static extern IntPtr CreateEvent(IntPtr lpEventAttributes, bool bManualReset, bool bInitialState, string lpName);
    }

    internal struct SECURITY_DESCRIPTOR 
    ...{
        internal byte Revision;
        internal byte Sbz1;
        internal short Control;
        internal IntPtr Owner;
        internal IntPtr Group;
        internal IntPtr Sacl;
        internal IntPtr Dacl;
    }

    internal struct SECURITY_ATTRIBUTES 
    ...{
        internal int nLength;
        internal IntPtr lpSecurityDescriptor;
        internal bool bInheritHandle;
    }
 
代码来源自 ClrSpy 源代码。
 

posted on 2005-02-26 04:11:00 by zee  评论(4) 阅读(5542)

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posted on 2005-02-24 06:59:00 by zee  评论(6) 阅读(4491)