How to generate a Guid in C#?

In C#, you can use the Guid(string s) constructor to parse a string into a Guid struct. The constructor accepts a string that represents a valid Guid and creates a Guid struct that contains the parsed value.

Here is an example of how to use the Guid(string s) constructor:

string guidString = "f06c3c8d-b2c2-4cc6-9a1a-8b3b3c82b9f0";
Guid guid = new Guid(guidString);

The Guid(string s) constructors throws a FormatException if the string is not in the correct format.

To avoid this exception, you can use the TryParse() method, which returns a boolean indicating whether the string was successfully parsed.

string guidString = "f06c3c8d-b2c2-4cc6-9a1a-8b3b3c82b9f0";
if (Guid.TryParse(guidString, out Guid guid))
{
    // use the Guid
}
else
{
    // handle error
}

Windows

On Windows, C#'s Guid.NewGuid() method generates a new globally unique identifier (GUID) using the CoCreateGuid Windows API function.

CoCreateGuid is a C++ function imported from the Windows OLE32 DLL that creates a 128-bit integer that is guaranteed to be unique across all devices and in all time. This makes it useful for creating persistent identifiers in distributed systems. Moreover, it uses the UuidCreate function to generate the new Guid, which ensures that the Guid generated can not be traced to the ethernet address of the computer on which it was generated and also it cannot be associated with other Guids created on the same computer.

Unix

On UNIX-based systems, the Guid.NewGuid() method uses a different approach to generate a new globally unique identifier. The method uses the Interop.GetRandomBytes() method to generate a random byte array of the same size as the Guid struct. Then it converts this byte array to the struct and modifies the bits indicating the type of the GUID.

This method ensures that the Guid generated is unique and random, but it does not use the ethernet address or any other unique hardware identifier, so it might not be as unique as the method used on Windows.

C# Guid generation cannot be considered random on the Windows platform because the Guid.NewGuid() method generates globally unique identifiers (GUIDs) using the CoCreateGuid C++ function that keeps persistent identifiers across environments. In other words, it tries to create a unique value (not necessarily random).

On UNIX-based systems, the Guid.NewGuid() generates a random byte array of the same size as the Guid struct. Because of that, Guids can be considered random in .NET applications running on UNIX-based systems.