Convert array type to singular

Question

In C# is it possible to convert an array type to singular - for use with Activator.CreateInstance. Take this for example:

void Main()
{
    var types = new[] { typeof(ExampleClass), typeof(ExampleClass[]) };
    var objects = new List<object>();

    foreach (var type in types)
    {
        // possibly convert type here? (from array to singular - type[] to type) 

        Debug.WriteLine($"{type}");
        objects.Add(Activator.CreateInstance(type));
    }
}

// Define other methods and classes here

public class ExampleClass
{
    public int X;
    public int Y;
}

Gets the following output:

What do you want to be returned? An array with zero elements? An array with one element? An instance of the element type of the array? Something else? — Matthew Watson, Sep 20 '17 at 08:42
Correct me if I'm wrong, but you're code has little to do with your question. You're asking about converting an array type, but in code you're just trying to create a new array (using reflection), which is failing because you didn't provide a parameter to the array constructor - the size of the array you're trying to create. — decPL, Sep 20 '17 at 08:45

score 1 · Answer 1 · answered Sep 20 '17 at 08:45

If I understand your Question right you might want something like this using Type.GetElementType() via reflection.

static void Main(string[] args)
    {

        var types = new[] { typeof(ExampleClass), typeof(ExampleClass[]) };
        var objects = new List<object>();

        foreach (var type in types)
        {
            var typeInstance = type.GetElementType();

            if (typeInstance != null)
            {
                Debug.WriteLine($"{typeInstance}");
                objects.Add(Activator.CreateInstance(typeInstance));
            }
            else
            {
                objects.Add(Activator.CreateInstance(type));
            }
        }
    }

   public class ExampleClass
   {
        public int X;
        public int Y;
   }

score 1 · Answer 2 · answered Sep 20 '17 at 08:47

If I understand your question correctly, you want to get the base-type of an array, right? That should be quite easy with the IsArray property of the type, simply check each entry of your list like this:

private static Type GetTypeOrElementType(Type type)
{
    if (!type.IsArray)
        return type;

    return type.GetElementType();
}

Btw, if you want to create a new Array of that specific type, you can use Array.CreateInstance instead of Activator.CreateInstance

score 0 · Accepted Answer · answered Sep 20 '17 at 09:28

Found this works:

void Main()
{
    var types = new[] { typeof(ExampleClass), typeof(ExampleClass[]) };
    var objects = new List<object>();

    foreach (var type in types)
    {
        Debug.WriteLine($"{type}");
        objects.Add(type.IsArray
                    ? Activator.CreateInstance(type, 1)
                    : Activator.CreateInstance(type));
    }
}

// Define other methods and classes here

public class ExampleClass
{
    public int X;
    public int Y;
}

Convert array type to singular

3 Answers3