New Guid Method
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Initializes a new instance of the Guid structure.
public: static Guid NewGuid();
public static Guid NewGuid ();
static member NewGuid : unit -> Guid
Public Shared Function NewGuid () As Guid
A new GUID object.
The following code example creates and displays the values of two Guid objects.
// Create and display the value of two GUIDs. Guid g = Guid.NewGuid(); Console.WriteLine(g); Console.WriteLine(Guid.NewGuid()); // This code example produces a result similar to the following: // 0f8fad5b-d9cb-469f-a165-70867728950e // 7c9e6679-7425-40de-944b-e07fc1f90ae7
' This code example demonstrates the Guid.NewGuid() method. Class Sample Public Shared Sub Main() Dim g As Guid ' Create and display the value of two GUIDs. g = Guid.NewGuid() Console.WriteLine(g) Console.WriteLine(Guid.NewGuid()) End Sub End Class ' 'This code example produces the following results: ' '0f8fad5b-d9cb-469f-a165-70867728950e '7c9e6679-7425-40de-944b-e07fc1f90ae7 '
This is a convenient
static method that you can call to get a new Guid. The method creates a Version 4 Universally Unique Identifier (UUID) as described in RFC 4122, Sec. 4.4. The returned Guid is guaranteed to not equal Guid.Empty.
On Windows, this function wraps a call to the CoCreateGuid function. The generated GUID contains 122 bits of strong entropy.
On non-Windows platforms, starting with .NET 6, this function calls the OS's underlying cryptographically secure pseudo-random number generator (CSPRNG) to generate 122 bits of strong entropy. In previous versions of .NET, the entropy is not guaranteed to be generated by a CSPRNG.
It is recommended that applications not use the NewGuid method for cryptographic purposes. First, since a Version 4 UUID has a partially predictable bit pattern, the NewGuid function cannot serve as a proper cryptographic pseudo-random function (PRF). If the output of NewGuid is given to a cryptographic component which requires its input to be generated by a proper PRF, the cryptographic component may not be able to maintain its security properties. Second, NewGuid utilizes at most 122 bits of entropy, regardless of platform. Some cryptographic components set a minimum entropy level on their inputs as a matter of policy. Such policies often set the minimum entropy level at 128 bits or higher. Passing the output of NewGuid to such a routine may violate its policy.
If an application requires random data for cryptographic purposes, consider using a static method on the RandomNumberGenerator class. That class provides a random number generator suitable for cryptographic use.