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What is "int?"  ??

Posted on 2012-03-22
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Last Modified: 2012-03-22
In C#:

 public int? blue_green_apps { get; set; }


why the "?" after the int?

Not familiar with this syntax.
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Question by:knowlton
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by:joshbula
joshbula earned 400 total points
ID: 37753142
It just means it's nullable.  It either has value (the value of the int) or can have no value (null).
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by:knowlton
ID: 37753212
How long has this syntax been around?

Is it unique to MVC or is it part of C# everywhere?
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Accepted Solution

by:
Anil Golamari earned 100 total points
ID: 37753273
http://msdn.microsoft.com/en-us/library/b3h38hb0%28v=vs.80%29.aspx

Just more information to Joshbula already mentioned above regarding int?

This syntax is supported right now .Net 2.0 framework.
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Expert Comment

by:joshbula
ID: 37753311
I'm not sure how long it's been around, and I'm pretty sure it's part of C# everywhere.  There's even a way to do it in Visual Basic as well, but I think the question mark goes after the variable instead.
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by:knowlton
ID: 37753346
I'm not sure how long it's been around, and I'm pretty sure it's part of C# everywhere.  There's even a way to do it in Visual Basic as well, but I think the question mark goes after the variable instead.

Thanks for the follow-up.

Thank you both for your time!
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by:knowlton
ID: 37753353
Accepted and Assisted solutions are backwards.  Not the points, just the distinction of Accepted vs Assisted.
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LVL 40
ID: 37755657
Yes, you can do it in VB by putting the ? after the name of the variable.

But personnally, I do not like that syntax, either in VB or in C#, because it is simply a shortcut to declaring a variable of the Nullable type:

public Nullable<int> blue_green_apps {get; set;}

The result is the same (int? creates a Nullable<int>), but the "standard" declaration makes it easier for everybody to understand what is happening.
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