Chapter 24: Guid

GUID (or UUID) is an acronym for 'Globally Unique Identifier' (or 'Universally Unique Identifier'). It is a 128-bit integer number used to identify resources.

Section 24.1: Getting the string representation of a Guid

A string representation of a Guid can be obtained by using the built in ToString method

string myGuidString = myGuid.ToString();

Depending on your needs you can also format the Guid, by adding a format type argument to the ToString call.

var guid = new Guid("7febf16f-651b-43b0-a5e3-0da8da49e90d");

//None "7febf16f651b43b0a5e30da8da49e90d"

Console.WriteLine(guid.ToString("N"));

//Hyphens "7febf16f-651b-43b0-a5e3-0da8da49e90d"

Console.WriteLine(guid.ToString("D"));

//Braces "{7febf16f-651b-43b0-a5e3-0da8da49e90d}"

Console.WriteLine(guid.ToString("B"));

//Parentheses "(7febf16f-651b-43b0-a5e3-0da8da49e90d)"

Console.WriteLine(guid.ToString("P"));

//Hex "{0x7febf16f,0x651b,0x43b0{0xa5,0xe3,0x0d,0xa8,0xda,0x49,0xe9,0x0d}}"

Console.WriteLine(guid.ToString("X"));

Section 24.2: Creating a Guid

These are the most common ways to create an instance of Guid:

Creating an empty guid (00000000-0000-0000-0000-000000000000):

Guid g = Guid.Empty;

Guid g2 = new Guid();

Creating a new (pseudorandom) Guid:

Guid g = Guid.NewGuid();

Creating Guids with a specific value:

Guid g = new Guid("0b214de7-8958-4956-8eed-28f9ba2c47c6");

Guid g2 = new Guid("0b214de7895849568eed28f9ba2c47c6");

Guid g3 = Guid.Parse("0b214de7-8958-4956-8eed-28f9ba2c47c6");

Section 24.3: Declaring a nullable GUID

Like other value types, GUID also has a nullable type which can take null value.

Declaration :

Guid? myGuidVar = null;

This is particularly useful when retrieving data from the data base when there is a possibility that value from a table is NULL.