Create GUID in C# (Various examples)

In previous article, I mentioned how to Convert JSON to CSV in C# but in this article, I have mentioned what is GUID in C# and how we can create GUID in C# or generate GUID with various examples.

What is GUID in C#?

GUID represent a Globally unique identifier (GUID). A GUID is a 128-bit integer (16 bytes) that you can use across all computers and networks wherever a unique identifier is required.

Guids are most often used as primary keys in databases. Their advantage is that you don't have to call the database to get a new ID that is (almost) guaranteed to be unique.

System.GUID class represents a GUID in .NET Framework.

Create or Generate GUID in C#

You can simply use Guid.NewGuid() to create new GUID in C#, here is the complete console application example, which generates GUID

using System;
					
public class Program
{
	public static void Main()
	{
		 Guid obj = Guid.NewGuid();    
         Console.WriteLine("Guid generated is " + obj.ToString());     
	}
}

Output:

If you will see above code and note, we are using Guid.NewGuid() not new GUID(), as we usually do while creating a class instance.

If you will use new Guid(), it will always generate empty string (16 byte with all 0)

What is the string length of a GUID?

It depends on how you format the Guid:

• Guid.NewGuid().ToString() = 36 characters (Hyphenated), output -> 12345678-1234-1234-1234-123456789abc
• Guid.NewGuid().ToString("D") = 36 characters (Hyphenated, same as ToString()),  outputs -> 12345678-1234-1234-1234-123456789abc
• Guid.NewGuid().ToString("N") = 32 characters (Digits only), outputs -> 12345678123412341234123456789abc
• Guid.NewGuid().ToString("B") = 38 characters (Braces), output -> outputs: {12345678-1234-1234-1234-123456789abc}
• Guid.NewGuid().ToString("P") = 38 characters (Parentheses), outputs-> (12345678-1234-1234-1234-123456789abc)
• Guid.NewGuid().ToString("X") = 68 characters (Hexadecimal), outputs -> {0x12345678,0x1234,0x1234{0x12,0x34,0x12,0x34,0x56,0x78,0x9a,0xbc}}

Generate GUID with specific length

You cannot do that using GUID.NewGUID() method, but you can create your own custom function (not recommended, as A GUID with a user-defined length is no longer a GUID.)

using System;
using System.Text;
					
public class Program
{
	public static void Main()
	{
		 Console.WriteLine(generateRandomStr(18));
	}
	
	public static string generateRandomStr(int length)
	{
		StringBuilder myGuidLikeString = new StringBuilder();
		while(myGuidLikeString.Length < length)
		{
			myGuidLikeString.Append(Guid.NewGuid().ToString());
		}
		return myGuidLikeString.ToString(0,length);
	}
	
}

Output:

740d0955-ae0d-4e11

OR

using System;
using System.Text.RegularExpressions;
					
public class Program
{
	public static void Main()
	{
		    Random rn = new Random();
			string charsToUse = "AzByCxDwEvFuGtHsIrJqKpLoMnNmOlPkQjRiShTgUfVeWdXcYbZa1234567890";

			MatchEvaluator RandomChar = delegate (Match m)
			{
				return charsToUse[rn.Next( charsToUse.Length )].ToString();
			};

			Console.WriteLine( Regex.Replace( "XXXX-XXXX-XXXX-XXXX-XXXX", "X", RandomChar ) );
			// 8J1P-fLcr-kwyt-4Mer-BDeT
			
	}
	
}

Create New Empty GUID (all zero)

You can use Guid.Empty which will create

Example

var guid = Guid.Empty;

OR

You can also create GUID with byte array and check if it is empty, using below code

var bytes = new Byte[16];
var guid2 = new Guid(bytes);
Console.WriteLine(guid2); // 00000000-0000-0000-0000-000000000000
Console.WriteLine($"{guid2 == Guid.Empty}"); //true

That's it, hope it clears your concepts related to GUID in C#.

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Get First Character or Nth Character of string in C#

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Generating GUID/UUID using Javascript (Various ways)

Uniqueidentifier in SQL Server