Convert an object that is an array to an array of objects

Question

How do you (in C#) convert an object that is an array to an array of objects

Something in the following format:

bool Compare(object valueToCompare)
{
   if(valueToCompare.IsArray())
   {
      foreach(var value in (valueToCompare as Array)){
          if(Compare(value));
             return true;
          return Compare(value);
      }
   }
   else
       return Compare(valueToCompare);
}

NOTE: The code above doesn't do much. I'm just prototyping.

You are only ever going to compare the first object in your array. Returning the result of Compare on the first value will ignore all other values in the array. — unholysampler
– unholysampler, Commented Feb 15, 2011 at 20:51

Adam Robinson · Accepted Answer · 2011-02-15 23:37:42Z

3

Assuming that the following are true:

valueToCompare is an array of reference types (not, say, an int[] or DateTime[])
The array that valueToCompare is one dimensional (so either declared as a one-dimensional array or a jagged array)

You can cast directly to an object[] instead of Array.

bool Compare(object valueToCompare)
{
   Type t = valueToCompare.GetType();

   if(t.IsArray() && !t.GetElementType().IsValueType && t.GetRank() == 1)
   {
      foreach(var value in (valueToCompare as object[]))
          return Compare(value);
   }
   else
   {
       return Compare(valueToCompare);
   }
}

If your array is of value types, then you're basically out of luck.

If your array is multi-dimensional, then you'll just have to write similar checks to account for as many dimensions as you want to support.

NOTE: As you've written it, this function will just call itself recursively (the else branch calls itself with the same parameters) and eventually result in a StackOverflowException. I don't believe this is what you intended to do, but I have left it as-is since I don't know what you actually wanted to do.

Additionally this won't actually compile. I'm not sure what your loop is intended to compare; as it is, it will just compare with the first element of the array, but if the array is empty then it won't return a value (hence the compilation error).

What are you trying to do here?

edited Feb 15, 2011 at 23:37

answered Feb 15, 2011 at 20:48

Adam Robinson

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8 Comments

n8wrl Over a year ago

Will the non-array branch result in a stack overflow?

Adam Robinson Over a year ago

@n8wrl: It sure will; I didn't even examine that portion of the code.

Tawani Over a year ago

It WILL NOTE result in a stackoverflow

Adam Robinson Over a year ago

@Tawani: As it's written, it will. You might want to clarify your question, or at least post some example code that's a little closer to what you're actually doing.

Eric Lippert Over a year ago

Note that only arrays where the element type is a reference type may be cast to object[]. An array of structs can (mostly) only be cast to an array of that kind of struct. (I say "mostly" because the CLR does permit some unusual conversions, like int[] to uint[].)

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