What is 'long?' data type?

c# nullable
xbonez picture xbonez · Oct 8, 2010 · Viewed 70.9k times · Source

I am going over some code written by another developer and am not sure what long? means:

protected string AccountToLogin(long? id)
{
   string loginName = "";
   if (id.HasValue)
   {
      try
      {....

Answer

Robert Greiner picture Robert Greiner · Oct 8, 2010

long is the same as Int64

long data type

The ? means it is nullable

A nullable type can represent the normal range of values for its underlying value type, plus an additional null value

Nullable Types

Nullable example:

int? num = null;
if (num.HasValue == true)
{
    System.Console.WriteLine("num = " + num.Value);
}
else
{
    System.Console.WriteLine("num = Null");
}

This allows you to actually check for a null value instead of trying to assign an arbitrary value to something to check to see if something failed.

I actually wrote a blog post about this here.

Related questions

How to convert C# nullable int to int

How do I convert a nullable int to an int? Suppose I have 2 type of int as below: int? v1; int v2; I want to assign v1's value to v2. v2 = v1; will cause an error. How do I …

Read More
nullable object must have a value

There is paradox in the exception description: Nullable object must have a value (?!) This is the problem: I have a DateTimeExtended class, that has { DateTime? MyDataTime; int? otherdata; } and a constructor DateTimeExtended(DateTimeExtended myNewDT) { this.MyDateTime = myNewDT.MyDateTime.Value; this.…

Read More
How to set enum to null

I have an enum string name; public enum Color { Red, Green, Yellow } How to set it to NULL on load. name = ""; Color color = null; //error Edited: My bad, I didn't explain it properly. But all the answers related to nullable …

Read More