NewGuid vs System.Guid.NewGuid().ToString("D");

Question

Is there a difference when you generate a GUID using NewGuid(); vs System.Guid.NewGuid().ToString("D"); or they are the same thing?

Answer 1

I realize that this question already has an accepted answer, but I thought it would be useful to share some information about formatting guids.

The ToString() (no parameters) method formats a guid using this format:

xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx

The ToString(string format) method formats a guid in one of several ways:

"N" - xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx (32 digits)
"D" - xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx (32 digits separated by hyphens)
"B" - {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx} (same as "D" with addition of braces)
"P" - (xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx) (same as "D" with addition of parentheses)
"X" - {0x00000000,0x0000,0x0000,{0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00}}

Calling Guid.ToString("D") yields the same result as calling Guid.ToString().

As mentioned in the other answers, the guid itself has no format. It is just a value. Note, that you can create guids using NewGuid or using the guid's constructor. Using NewGuid, you have no control over the value of the guid. Using the guid's constructor, you can control the value. Using the constructor is useful if you already have a string representation of a guid (maybe you read it from a database) or if you want to make it easier to interpret a guid during development. You can also use the Parse, ParseExact, TryParse, and TryParseExact methods.

So, you can create guids like this:

Guid g1 = Guid.NewGuid(); //Get a Guid without any control over the contents
Guid g2 = new Guid(new string('A',32)); //Get a Guid where all digits == 'A'
Guid g3 = Guid.Parse(g1.ToString());
Guid g4 = Guid.ParseExact(g1.ToString("D"),"D");
Guid g5;
bool b1 = Guid.TryParse(g1.ToString(), out g5);
Guid g6;
bool b2 = Guid.TryParseExact(g1.ToString("D"),"D", out g6);