if statements matching multiple values

How about:

if (new[] {1, 2}.Contains(value))

It's a hack though :)

Or if you don't mind creating your own extension method, you can create the following:

public static bool In<T>(this T obj, params T[] args)
{
    return args.Contains(obj);
}

And you can use it like this:

if (1.In(1, 2))

:)

A more complicated way :) that emulates SQL's 'IN':

public static class Ext {    
    public static bool In<T>(this T t,params T[] values){
        foreach (T value in values) {
            if (t.Equals(value)) {
                return true;
            }
        }
        return false;
    }
}

if (value.In(1,2)) {
    // ...
}

But go for the standard way, it's more readable.

EDIT: a better solution, according to @Kobi's suggestion:

public static class Ext {    
    public static bool In<T>(this T t,params T[] values){
        return values.Contains(t);
    }
}