What is 'long?' data type?

Question

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
      {....

Robert Greiner · Accepted Answer · 2012-12-10T19:29:40.160

74

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.

edited Dec 10 '12 at 19:29

answered Oct 08 '10 at 18:10

Robert Greiner

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Links in answer are outdated. – Pang Apr 15 '21 at 03:50
1

Blog post is 404. – Thorbjørn Ravn Andersen Nov 16 '21 at 14:28

score 15 · Answer 2 · edited Oct 08 '10 at 18:20

15

long is an Int64, the ? makes it nullable.

edited Oct 08 '10 at 18:20

Steve Guidi

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answered Oct 08 '10 at 18:10

Lucero

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score 6 · Answer 3 · edited Jul 08 '15 at 16:14

6

long? is a 64-bit, nullable integer.

To clarify, nullable means it can be null or an integer number ( 0, 1, etc.).

edited Jul 08 '15 at 16:14

Peter Mortensen

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answered Oct 08 '10 at 18:10

automagic

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score 6 · Answer 4 · edited Oct 08 '10 at 18:12

6

"long?" is a nullable 64-bit signed integer. It's equivalent to Nullable<Int64>.

edited Oct 08 '10 at 18:12

Lucero

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answered Oct 08 '10 at 18:11

Peter

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score 4 · Answer 5 · answered Oct 08 '10 at 18:12

4

long? is a nullable type. This means that the id parameter can have a long value or be set to null. Have a look at the HasValue and Value properties of this parameter.

answered Oct 08 '10 at 18:12

Bernard

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score 3 · Answer 6 · edited Jul 08 '15 at 16:15

3

It's a nullable type declaration.

edited Jul 08 '15 at 16:15

Peter Mortensen

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answered Oct 08 '10 at 18:12

Joel Etherton

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What is 'long?' data type?

6 Answers6

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