C# converting an array returned as a generic object to a different underlying type

Question

I have a C# method which uses object as a generic container to return a data array which could be declared using different data types. Below a simplified example of such a method:

void GetChannelData(string name, out object data)
{
    // Depending on "name", the underlying type of  
    // "data" can be different: int[], byte[], float[]...
    // Below I simply return int[] for the sake of example
    int[] intArray = { 0, 1, 2, 3, 4, 5 };
    data = intArray;
}

I need to convert all the returned array elements to double but so far I could not find a way. Ideally I would like to perform something like:

object objArray;
GetChannelData("test", out objArray);
double[] doubleArray = Array.ConvertAll<objArray.GetType().GetElementType(), double>(objArray, item => (double)item);

Which miserably fails because ConvertAll does not accept types defined at runtime. I have also tried intermediate conversions to a dynamic variable, to no avail.

Is there any way to perform such type conversion in a simple manner?

All the provided answers are working fine; accepted the @AlexWiese version as correct answer as he provided such solution before AnyName. Thanks to all of you guys! — Metal76
– Metal76, Commented Feb 25, 2017 at 12:33

Alex Wiese · Accepted Answer · 2017-02-25 12:20:29Z

4

If you don't know the type at compile time you can try to convert it.

var array = (IEnumerable)objArray;
var doubles = array.OfType<object>().Select(a => Convert.ToDouble(a)).ToArray();

answered Feb 25, 2017 at 12:20

Alex Wiese

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Hoang Hiep · Accepted Answer · 2017-02-25 12:29:24Z

3

If you don't know the type of array elements at compile-time:

var doubleArray = (objArray as Array).OfType<object>()
    .Select(m => Convert.ToDouble(m)).ToArray();

edited Feb 25, 2017 at 12:29

answered Feb 25, 2017 at 11:57

Hoang Hiep

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3 Comments

Metal76 Over a year ago

Yes, unfortunately the library method returns an object and not an object[], so Select does not apply.

Hoang Hiep Over a year ago

@Nkosi I didn't notice that. I've just updated my answer.

Metal76 Over a year ago

@AnyName, nice way but you actually convert to int at compile time, while I am just able to read the underlying type at runtime with a GetType(). Maybe my example is not 100% clear, I will try to edit it so that it is clearer

levent · Accepted Answer · 2017-02-25 12:26:31Z

1

u can create extension method..

        public static IEnumerable<T> Convert<T>(this IEnumerable source)
        {
           foreach (var item in source)
               yield return (T)System.Convert.ChangeType(item, typeof(T));
        }

using ..

        object objArray;
        GetChannelData("test", out objArray);
        var array = (IEnumerable)objArray;
        var doubleArray = array.Convert<double>().ToArray();

edited Feb 25, 2017 at 12:26

answered Feb 25, 2017 at 12:19

levent

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