If statement simplification in C#

Question

I have a line of code that looks like this:

if (obj is byte || obj is int || obj is long || obj is decimal || obj is double || obj is float)

Is it possible to write something more elegant than this? Something like:

if (obj is byte, int, long)

I know that my example isn't possible, but is there a way to make this look "cleaner"?

It's not necessarily just for numeric types, I need to compare against custom types as well. — Jon Tackabury, Jul 28 '09 at 15:21

score 27 · Accepted Answer · answered Jul 28 '09 at 14:18

27

You could write an extension method on object to give you syntax like:

if (obj.Is<byte, int, long>()) { ... }

Something like this (use multiple versions for fewer or more generic arguments:

public static bool Is<T1, T2, T3>(this object o)
{
    return o is T1 || o is T2 || o is T3;
}

answered Jul 28 '09 at 14:18

Jason

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4

I would name the method IsOneOf, but this is a very concise syntax indeed. – jeroenh Jul 28 '09 at 14:23
1

shame you can't use something like params for generic parameters – Matthew Whited Jul 28 '09 at 15:07
@Matthew, I wonder if one could define `interface ITuple` and then subclass it with a variety of tuple generic classes (`Tuple : ITuple`, `Tuple : ITuple`, etc). Then redo the extension method as `Is where TTuple : ITuple`.. Then unwrap the generic type arguments inside of the method.. This would give `params`-like generic argument functionality... – Jason Jul 28 '09 at 16:00

score 12 · Answer 2 · answered Jul 28 '09 at 14:17

12

Only:

static readonly HashSet<Type> types = new HashSet<Type> 
    { typeof(byte), typeof(int), typeof(long) etc };

...

if (types.Contains(obj.GetType())
{
}

Or use obj.GetType().GetTypeCode().

answered Jul 28 '09 at 14:17

Jon Skeet

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score 8 · Answer 3 · answered Jul 28 '09 at 14:16

8

I would throw it into a method to simplify it a bit:

private static bool ObjIsNumber(object obj)
{
    return  (obj is byte || obj is int || obj is long || 
             obj is decimal || obj is double || obj is float);
}

answered Jul 28 '09 at 14:16

jjnguy

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You beat me to it. Upvoting you. – NotMe Jul 28 '09 at 14:20

score 3 · Answer 4 · answered Jul 28 '09 at 14:16

3

Why don't you do this?

bool IsRequestedType(object obj)
{
    if (obj is byte || obj is int || obj is long || obj is decimal || obj is double || obj is float)
         return true;
    return false;
}

Or you might be able to get away with

obj is IComparable

answered Jul 28 '09 at 14:16

Daniel A. White

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2

cmon, `if (true) return true; else return false;` - Ishy. – jjnguy Jul 28 '09 at 14:20
1

Or simply: bool IsRequestedType(object obj) { return obj is byte || obj is int || obj is long || obj is decimal || obj is double || obj is float; } – Jesper Fyhr Knudsen Jul 28 '09 at 14:21
obj is IComparable would also allow string... probably not what he wants. – Powerlord Jul 28 '09 at 14:22
@arkain, that is what i did in my answer. – jjnguy Jul 28 '09 at 14:22
@ jinguy, hadn't scrolled that far down yet, when I wrote, I have upvoted you. – Jesper Fyhr Knudsen Jul 28 '09 at 14:26

score 1 · Answer 5 · answered Jul 28 '09 at 14:17

1

That looks fine to me - nice and clear.

answered Jul 28 '09 at 14:17

Justin

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score 1 · Answer 6 · edited Jul 28 '09 at 14:57

1

Create a helper function to put your test in.

Something like

public static Boolean IsNumeric(Object myObject) {
    return (obj is byte || obj is int || obj is long || obj is decimal || obj is double|| obj is float);
}

edited Jul 28 '09 at 14:57

jjnguy

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answered Jul 28 '09 at 14:19

NotMe

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score 1 · Answer 7 · answered Jul 28 '09 at 14:20

public static bool IsOneOf(object o, params Type[] types)
{
    foreach(Type t in types)
    {
        if(o.GetType() == t) return true;   
    }

    return false;
}

long l = 10;
double d = 10;
string s = "blah";

Console.WriteLine(IsOneOf(l, typeof(long), typeof(double))); // true
Console.WriteLine(IsOneOf(d, typeof(long), typeof(double))); // true
Console.WriteLine(IsOneOf(s, typeof(long), typeof(double))); // false

If statement simplification in C#

7 Answers7

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