Casting an array of integers to an array of enums

Question

I have an enum that has 4 values:

public enum DriveRates 
{ 
    driveSidereal = 0,
    driveLunar = 1, 
    driveSolar = 2, 
    driveKing = 3 
}

I have an array of values that I want to cast to an array of DriveRates. However when I do var rates = (DriveRates[])ret;, with ret being an object array of numbers (probably integers), it says Unable to cast object of type 'System.Object[]' to type 'ASCOM.DeviceInterface.DriveRates[]'.

ret={0,1,2,3}. How should I do this instead. Again, I am trying to convert an array of enum values to an array of enum...well, values :) But I'm trying to convert from type object[] to type DriveRates[].

Jon Skeet · Accepted Answer · 2013-03-01 23:52:05Z

26

You can't just cast the array, if it's really an object[]. You can create a new array pretty easily though:

var enumArray = originalArray.Cast<DriveRates>().ToArray();

If it were actually an int[] array to start with, you could cast - although you'd have to talk nicely to the C# compiler first:

using System;

class Program
{
    enum Foo
    {
        Bar = 1,
        Baz = 2
    }

    static void Main()
    {
        int[] ints = new int[] { 1, 2 };
        Foo[] foos = (Foo[]) (object) ints;
        foreach (var foo in foos)
        {
            Console.WriteLine(foo);
        }
    }
}

The C# compiler doesn't believe that there's a conversion from int[] to Foo[] (and there isn't, within the rules of C#)... but the CLR is fine with this conversion, so as long as you can persuade the C# compiler to play along (by casting to object first) it's fine.

This doesn't work when the original array is really an object[] though.

answered Mar 1, 2013 at 23:52

Jon Skeet

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3 Comments

Arlen Beiler Over a year ago

Hmm...Yes, it's an array of objects. Apparently an array of objects can't be converted to an array of ints.

Jon Skeet Over a year ago

@ArlenBeiler: Well it can be converted to a new array - but the existing array can't be just treated as an array of ints, as they have different representations.

quetzalcoatl Over a year ago

It's worth noticing, that even is and as operators may get confused with types of enum arrays, see the last snippet at stackoverflow.com/a/21186137/717732 - all three checks say 'true', while .GetType() of course says not.

JaredPar · Accepted Answer · 2013-03-01 23:51:38Z

1

This isn't possible. There is no way to cast between an array of reference types and an array of value types. You will need to manually copy the elements into the new array

DriveRates[] Convert(object[] source) { 
  var dest = new DriveRates[source.Length];
  for (int i = 0; i < source.Length; i++) { 
    dest[i] = (DriveRates)source[i];
  }
  return dest;
}

answered Mar 1, 2013 at 23:51

JaredPar

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Comments

Valikoo Vakh · Accepted Answer · 2017-12-12 19:40:52Z

0

...or with linq, especially if you need to do some extra things with every element in one line:

DriveRates[] enumArray = originalArray.Select(o => (DriveRates)o).ToArray();

answered Dec 12, 2017 at 19:40

Valikoo Vakh

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