object to string array

Question

I am trying to convert an object (is declared here as 'obj': object is array, primitive) to a string array.

object can be anything uint[], int16[], etc.

I have been trying to use

string[] str = Array.ConvertAll<object, string>((object[])obj, Convert.ToString); 

The problem occurs when I try to cast the unknown type object into object[]. I have been getting casting error.

One attempt I made, which failed, was using

object[] arr = (object[])obj; 

or

IEnumerable<object> list = obj as IEnumerable<object> object[] arr = (object[])list; 

I saw postings regarding value type and reference type issue on casting.

Would there be a simple code that can handle casting to object[] regardless of type of object, as long as it is an array ? I am trying to avoid manual handling of every possible type casting.

thanks in advance

Answer 1

You can use the fact that every array implements IEnumerable:

string[] arr = ((IEnumerable)obj).Cast<object>()                                  .Select(x => x.ToString())                                  .ToArray(); 

This will box primitives appropriately, before converting them to strings.

The reason the cast fails is that although arrays of reference types are covariant, arrays of value types are not:

object[] x = new string[10]; // Fine object[] y = new int[10]; // Fails 

Casting to just IEnumerable will work though. Heck, you could cast to Array if you wanted.

Answer 2

If it's always a collection of some type (array, list, etc ...) then try casting back to plain old System.Collections.IEnumerable and go from there

string[] str = ((System.Collections.IEnumerable)obj)   .Cast<object>()   .Select(x => x.ToString())   .ToArray(); 

Here is a more thorough implementation that handles non-collections as well

static string[] ToStringArray(object arg) {   var collection = arg as System.Collections.IEnumerable;   if (collection != null) {     return collection       .Cast<object>()       .Select(x => x.ToString())       .ToArray();   }    if (arg == null) {     return new string[] { };   }    return new string[] { arg.ToString() }; }