guid

Possible Duplicate: Is a GUID unique 100% of the time? Simple proof that GUID is not unique In MSDN you can read: The chance that the value of the new Guid will be all zeros or equal to any other Guid is very low. Say that you have an method that will create a file every second, and you use the method Guid.NewGuid() for filename, is it possible to get the same Guid then? Or will the local computer keep track in some way? How low is the chance ? You would never run out of guids. The likelihood of duplicating them is VERY low: http://betterexplained.com/articles/the-quick-guide-to-guids/ The

I've registered a window with RegisterDeviceNotification and can successfully recieve DEV_BROADCAST_DEVICEINTERFACE messages. However, the dbcc_name field in the returned struct is always empty. The struct I have is defined as such: [StructLayout(LayoutKind.Sequential)] public struct DEV_BROADCAST_DEVICEINTERFACE { public int dbcc_size; public int dbcc_devicetype; public int dbcc_reserved; public Guid dbcc_classguid; [MarshalAs(UnmanagedType.LPStr)] public string dbcc_name; } And I'm using Marshal.PtrToStructure on the LParam of the WM_DEVICECHANGE message. Should this be working? Or even

I have a database where 2 (or maybe 3 or 4) different applications are inserting information. The new information has IDs of the type GUID/UUID, but each application is using a different algorithm to generate the IDs. For example, one is using the NHibernate's "guid.comb", other is using the SQLServer's NEWID(), other might want to use .NET's Guid.NewGuid() implementation. Is there an above normal risk of ID collision or duplicates? Thanks! Aaronaught The risk of collisions is elevated slightly but still vanishingly small. Consider that: Both Comb and NEWID / NEWSEQUENTIALID include a

What is the necessity for the GUID attribute? why don't just let the compiler handle this automatically?! If the compiler handled this automatically, you'd end up with one of two situations. A new GUID every time you compiled - since GUIDs are supposed to be published, this would fail. Collisions - if the GUID was the same every time, based on (say) a Hash of the name, multiple projects would end up using the same GUID for different purposes. The existing approach - an explicit GUID gives developers the power to control these as required. These are attributes that matter a great deal to COM.

I hope someone can answer this question. How does the UuidCreateSequential method in the rpcrt4.dll class use to seed it's guids? I know this much: Microsoft changed the UuidCreate function so it no longer uses the machine's MAC address as part of the UUID. Since CoCreateGuid calls UuidCreate to get its GUID, its output also changed. If you still like the GUIDs to be generated in sequential order (helpful for keeping a related group of GUIDs together in the system registry), you can use the UuidCreateSequential function. The reason behind the question is. If I use this function to generate

I'm testing out some WCF services that send objects with Guids back and forth. In my web app test code, I'm doing the following: var responseObject = proxy.CallService(new RequestObject { Data = "misc. data", Guid = new Guid() }); For some reason, the call to new Guid() is generating Guids with all 0's (zeros) like this: 00000000-0000-0000-0000-000000000000 What could be causing this? Use the static method Guid.NewGuid() instead of calling the default constructor. var responseObject = proxy.CallService(new RequestObject { Data = "misc. data", Guid = Guid.NewGuid() }); Lessons to learn from

I am faced with the dilemma of changing my primary keys from int identities to Guid. I'll put my problem straight up. It's a typical Retail management app, with POS and back office functionality. Has about 100 tables. The database synchronizes with other databases and receives/ sends new data. Most tables don't have frequent inserts, updates or select statements executing on them. However, some do have frequent inserts and selects on them, eg. products and orders tables. Some tables have upto 4 foreign keys in them. If i changed my primary keys from 'int' to 'Guid', would there be a

第一种方式 public async Task SendMessageAsync(string topic, string message) { var guid = Guid.NewGuid().ToString("N"); var topics = new List<string> { this._kafkaSetting.ProducerTopics.DeviceTopic, this._kafkaSetting.ProducerTopics.StorageTopic, this._kafkaSetting.ProducerTopics.TaskTopic, this._kafkaSetting.ConsumerTopics.StorageTopic, this._kafkaSetting.ConsumerTopics.TaskTopic }; if (!topics.Contains(topic)) { this._logger?.LogError($"guid:{guid} SendMessageAsync error: ' topic:{topic} error"); return; } this._logger?.LogDebug($"guid:{guid} SendMessageAsync begin: ' topic:{topic},message: