整数字段设置为空

Question

How to make an integer field accepts null values?

[Range(10, 65]
[Display(Name = "oh")]
public int oh { get; set; }

I'm currently using this code, but I'm getting not null on sql server (I haven't used [Required]).

Thanks a lot!

Answer 1

Use ? keyword

public int? oh { get; set; }

It makes the type a Nullable type. Now you can set null to oh

And then check for its value by:

if(oh.HasValue){
  Console.WriteLine(oh.Value)
}

.HasValue says if it has value or null.

.Value gets you the actual value

Answer 2

use

int? for the data type.

I don't know how this will work in conjunction with Range...

Answer 3

You can use a nullable type:

int? intNullable = null;

With a nullable type, you have another features like a bool property called HasValue which return if the int has a value and Value to get a value without nullable.

if (intNullable.HasValue)
{
    int value = intNullable.Value;
}

In your case

public int? oh { get; set; }

The difference it the int is a value type while int? is a reference type. The ? is just a shortcut to Nullable<T> class. Value types cannot be null, reference type can. Read more about here http://msdn.microsoft.com/en-us/library/t63sy5hs.aspx

Answer 4

You can use ? in cases where a value type might be null:

public int? oh { get; set; }