nullable types

[Tony Johansson]

Hello!

These two declarations(1 and 2) are the same I assume.
1. System.Nullable <intnullable;
2. System.Nullable <intnullable = new System.Nullable <int();

So because these 1 and 2 are the same is no point to use the longer
declaration as 2 it good enough
to use decaration 1.

Do you agree with me?
The declaration of nullable above a value type or a reference type?

//Tony

[=?Utf-8?B?S0g=?=]

RE: nullable types

The first one can't be used until it is assigned a value, so

Nullable<intnul lable;
Console.WriteLi ne( nullable.HasVal ue ); // Compiler error here

Nullable<intnul lable = new Nullable<int>() ;
Console.WriteLi ne( nullable.HasVal ue ); // OK

You can also use the ? shorthand in C# for nullable types:

int? nullable = null; // same as second example above

HTH


"Tony Johansson" wrote:

Hello!
>
These two declarations(1 and 2) are the same I assume.
1. System.Nullable <intnullable;
2. System.Nullable <intnullable = new System.Nullable <int();
>
So because these 1 and 2 are the same is no point to use the longer
declaration as 2 it good enough
to use decaration 1.
>
Do you agree with me?
The declaration of nullable above a value type or a reference type?
>
//Tony
>
>
>

[Jon Skeet [C# MVP]]

Re: nullable types

Tony Johansson <johansson.ande rsson@telia.com wrote:

These two declarations(1 and 2) are the same I assume.
1. System.Nullable <intnullable;
2. System.Nullable <intnullable = new System.Nullable <int();

Not for local variables. A local variable declared as per 1 has no
definitely assigned value. In other words, this won't compile:

void Invalid()
{
System.Nullable <intnullable;
if (nullable == null)
{
Console.WriteLi ne("Null");
}
}

whereas this will:

void Valid()
{
System.Nullable <intnullable = new System.Nullable <int>;
if (nullable == null)
{
Console.WriteLi ne("Null");
}
}

So because these 1 and 2 are the same is no point to use the longer
declaration as 2 it good enough
to use decaration 1.

Well, I'd generally use:

int? nullable;
or
int? nullable = null;

The latter is potentially slightly clearer to readers.

Do you agree with me?
The declaration of nullable above a value type or a reference type?

A nullable value type is still a value type. When the null literal is
used (as above) with a nullable value type, it represents the "null
value" of the type, which is the value where HasValue returns false.

--
Jon Skeet - <skeet@pobox.co m>
Web site: http://www.pobox.com/~skeet
Blog: http://www.msmvps.com/jon.skeet
C# in Depth: http://csharpindepth.com