How do I generate an ID that is garunteed to be unique? [duplicate]

Question

I need to garuntee the uniqueness of an ID. Even if there's a 1 in 1 trillion chance of there being a dupe, I cannot use it.

But I don't really feel like going to the ends of the earth to find a solution either. I have spent some time looking into this, and everything I have found to date isn't able to garuntee me a unique ID.

So I thought I would use something very simple, like this:

    public static string GenerateItemID()
    {
        string year = DateTime.Now.Year.ToString(), 
            month = DateTime.Now.Month.ToString(), 
            day = DateTime.Now.Day.ToString(), 
            hour = DateTime.Now.Hour.ToString(), 
            minute = DateTime.Now.Minute.ToString(), 
            second = DateTime.Now.Second.ToString(), 
            millisecond = DateTime.Now.Millisecond.ToString();

        return year + month + day + hour + minute + second + millisecond;
    }

My logic here is: each new UI that is generated can not possibly be the same as any of the previous ones. But then I wondered if it were possible for a PC to generate two or more of these ID's within the same millisecond? Naturally, I then looked in Intellisense for a Nanosecond property, but it doesn't exist.

How can I generate an ID that is garunteed to be unique?

Answer 1

var id = Guid.NewGuid(); 

I believe this will create a fairly unique id.

Answer 2

Let use GUID.

Refer here: https://msdn.microsoft.com/en-us/library/system.guid.newguid(v=vs.110).aspx

Hope this help.