restrict T to a int value?

How can i solve this error msg?

static publi开发者_运维百科c class Blah
{
    public static T val<T>(this bool b, T v) { return b == true? v:0; }
}

error

Type of conditional expression cannot be determined because there is no implicit conversion between 'T' and 'int

If you want T to be an int, accept an int and not a T. Otherwise, consider returning default(T) if b == false.

return b ? v : default(T);

If T is an int, it will return 0. If it is a reference type, it will be null. And on and on..

Why are you trying to use generics if you only want an int?

// No need to compare b to true...
public static int val(this bool b, int v) { return b ? v : 0; }

Otherwise, use default(T) as others have mentioned.

public static T val<T>(this bool b, T v) { return b ? v : default(T); }

default(T) will default to 0 for ints and other numeric values, false for bools, null for objects...

If you want to return the "default" value for T:

public static T val<T>(this bool b, T v) { return b == true? v : default(T); }

Default Values Table
default Keyword in Generic Code

There is no way to do this in C#. You can do

where T: struct, and force T to be a value type, but that still isn't enough.

Or you can do

default(T), which is 0 when T is an int.

Try replacing v : 0 with v : default(T) , if you have a good reason for generics. If you need to restrict it to int, then you're not writing a generic class.

If there's only valid type for T then it shouldn't be generic:

public static int val(this bool b, int v)
{
    return b ? v : 0;
}

If you want this to work for any value type you could do this:

public static int val<T>(this bool b, T v) where T : struct
{
    return b ? v : default(T);
}

Srsly!

To "restrict T to int" you take advantage of a special compiler feature known as strong-typing:

static public class Blah
{
    public static int val(this bool b, int v) { return b == true? v:0; }
}

Tada! :)

Seriously, why are you using generics?