Question

I have an object whose value may be one of several array types like int[] or string[], and I want to convert it to a string[]. My first attempt failed:

void Do(object value)
{
    if (value.GetType().IsArray)
    {
        object[] array = (object[])value;
        string[] strings = Array.ConvertAll(array, item => item.ToString());
        // ...
    }
}

with the runtime error Unable to cast object of type 'System.Int32[]' to type 'System.Object[]', which makes sense in retrospect since my int[] doesn’t contain boxed integers.

After poking around I arrived at this working version:

void Do(object value)
{
    if (value.GetType().IsArray)
    {
        object[] array = ((Array)value).Cast<object>().ToArray();
        string[] strings = Array.ConvertAll(array, item => item.ToString());
        // ...
    }
}

I guess this is OK, but it seems pretty convoluted. Anyone have a simpler way?

Answer 1

You don’t need to convert it to an array and then use LINQ. You can do it in a more streaming fashion, only converting to an array at the end:

var strings = ((IEnumerable) value).Cast<object>()
                                   .Select(x => x == null ? x : x.ToString())
                                   .ToArray();

(Note that this will preserve nulls, rather than throwing an exception. It’s also fine for any IEnumerable, not just arrays.)