GUID stands for Global Unique Identifier.
A GUID is a 128-bit integer (16 bytes) that you can use across all computers
and networks wherever a unique identifier is required.
Here are some frequently asked questions about GUIDs.
A. How many GUIDs in Microsoft Windows can one computer generate without
rolling over or running out?
Answer: Without getting into detail, let me tell you there are 2^122 or 5,316,911,983,139,663,491,615,228,241,121,400,000 possible combination.
Reason is beyond the scope of this article.
B. Which class in .NET Framework is used to generate Guid?
Answer: System.GUID class represents a GUID in .NET Framework.
C. How can we generate GUID with SQL Server?
Answer: We can generate GUID in Sql Server with the help of NEWID() function
D. Which namespace must be referenced to utilize the GUID attribute. ?
Answer: System.Runtime.InteropServices namespace must be referenced to utilize the GUID
attribute.
This can be done as shown in following code:-
using System;
using System.Runtime.InteropServices;
namespace TESTGUID {
[Guid("9245fe4a-d402-451c-b9ed-9c1a04247482")]
class Example {
//Your Implementation
}
} |
Generating GUID in .NET Framework using C#
We can generate GUID by calling following code snippet. As you can see from this code, we use Guid.NewGuid() method to generate a new GUID in C#.
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace ConsoleApplication5
{
class Program
{
static int Main(string[] args)
{
Guid obj = Guid.NewGuid();
Console.WriteLine("New Guid is " + obj.ToString());
Console.ReadLine();
return -1;
}
}
}
|
Note that above in above code we have used the NewGuid Method which will create
new GUID .
A common mistake done by C# developers is to create an object of GUID and trying to print
that.
The following code snippet reflects that mistake.
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace ConsoleApplication5
{
class Program
{
static int Main(string[] args)
{
Guid obj = new Guid();
Console.WriteLine("New Guid is " + obj.ToString());
Console.ReadLine();
return -1;
}
}
}
|
The output of above console program will be always be 16 byte with all 0 .
Everytime same thing will come.
So while generating GUID use NewGuid Method.
Also note that Guid only contains alphanumeric characters and none of
non-alphanumeric character will be seen in GUID except "-";
Hope it helps.