How to check if a variable is an IEnumerable of some sort

Question

basically I\'m building a very generic T4 template and one of the things I need it to do is say print variable.ToString(). However, I want it to evaluate lists and

Answer 1

If you don't care about object type and you are not in Generic method in C# 7.0+

        if (item is IEnumerable<object> enumVar)
        {
            foreach (var e in enumVar)
            {
                    e.ToString();

            }
        }

In C# < 7.0

        if (item is IEnumerable<object>)
        {
            var enumVar = item as IEnumerable<object>;
            foreach (var e in enumVar)
            {
                e.ToString();

            }
            //or you can cast an array to set values, 
            //since IEnumerable won't let you, unless you cast to IList :) 
            //but array version here 
            //https://stackoverflow.com/a/9783253/1818723
        }

Answer 2

You have already accepted an answer however,since generic IEnumerable<T> implements the non generic IEnumerable you can just cast to that.

// Does write handle null? Might need some sanity aswell.

var enumerable = variable as System.Collections.IEnumerable; 

if (enumerable != null)
    foreach(var item in enumerable)
         Write(item);
else
    Write(item);     

Answer 3

Since C# 7.0 you can also achieve this so:

if (variable is IEnumerable enumVar)
{
    foreach (var e in enumVar)
    {
        ...
    }
}

Answer 4

In general, with no non-generic base type/interface, this requires GetType and a recursive look-up through the base types/interfaces.

However, that doesn't apply here :-) Just use the non-generic IEnumerable (System.Collections.IEnumerable), from which the generic IEnumerable (System.Collections.Generic.IEnumerable<T>) inherits.

Answer 5

The other answers have pointed out the generic/non-generic IEnumerable difference but I should also point out that you will also want to test for String specifically because it implements IEnumerable but I doubt you'll want to treat it as a collection of characters.

Answer 6

You can actually test the base class of any generic type directly.

instance.GetGenericTypeDefinition()  == typeof(IEnumerable<>)