Method to handle multiple "Is" statements

Question

In my current code, I am testing for an object's type using if/else if & is:

public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        if (value is double)
        {
            //do something
        }
        else if (value is int)
        {
            //do something
        }
        else if (value is string)
        {
            //do something
        }
        else if (value is bool)
        {
            //do something
        }
       Type type = value.GetType();
       throw new InvalidOperationException("Unsupported type [" + type.Name + "]");
    }

Rather than having a long list of else if, I tried to condense all of the is statements using an Extension Method, but to no avail.

Here is my attempt at the Extension Method:

public static class Extensions
    {
        public static bool Is<T>(this T t, params T[] values)
        {
            return values.Equals(t.GetType());
        }
    }

and the method:

public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        if (value is double)
        {
            //do something
        }
        else if (value.Is<object>(int, string, bool))
        {
            //do something
        }

        Type type = value.GetType();
        throw new InvalidOperationException("Unsupported type [" + type.Name + "]");
  }

Does anyone know why this is failing? Any help would be greatly appreciated!

Answer 1

You need to pass it the types, not the class names. You should also use Contains instead of Equals:

public static bool IsAny(this object obj, params Type[] types)
{
    return types.Contains(obj.GetType());
}

if(value.IsAny(typeof(SolidColorBrush), typeof(LinearGradientBrush), typeof(GradientBrush), typeof(RadialGradientBrush)))
{
}

Contains matches the type exactly, so you might want to is IsSubclassOf or IsAssignableFrom instead

e.g

return types.Any(t => t.IsAssignableFrom(obj.GetType()));

Answer 2

So you have several problems here. The first of which is the line: values.Equals(t.GetType()). You're not checking each of the values of the collection, you're checking if the collection as a whole is equal to the one type. Since one is an object[] and one is a Type they'll never be equal. You need to check if Any of the values in the collection are equal to the type.

Next, you don't want the parameters to be a bunch of objects, you want them to be a bunch of Types.

Here is a better solution:

public static bool IsAny(this object obj, params Type[] types)
{
    return types.Any(type => type.IsAssignableFrom(obj.GetType()));
}

You would then use it like:

bool b = "a".IsAny(typeof(int), typeof(double), typeof(MyClass));