Unable to cast from object array to a string array

Question

This is my function.

public Dictionary<string, string> ArrayToDictionaryConverter(object [] objArray)
    {
        string[] strArray = new string[objArray.Length];
        strArray =(string[])objArray;
        Dictionary<string, string> dictionary = null;
        try
        {
            dictionary = new Dictionary<string, string>();
            for (int iVal = 0; iVal < strArray.Length; )
            {
                dictionary.Add(strArray[iVal], strArray[iVal + 1]);
                iVal += 2;
            }
        }
        catch (Exception ex)
        {
        }
        return dictionary;
    }

Getting error :

Unable to cast object of type 'System.Object[]' to type 'System.String[]'.

Why ? is this wrong convention / Casting?

See stackoverflow.com/questions/2016654/… for the correct answers to this question. — PP.
– PP., Commented Jul 13, 2010 at 10:41

Jon Skeet · Accepted Answer · 2009-12-31 08:38:46Z

6

You can't cast an expression to a particular type if it's not actually of that type, or a compatible one (or there's an explicit conversion).

In this case, the array wasn't a string[] - it was an object[]. It could have been a string[], which is why the compiler allowed you to write the cast in the first place - but at execution time the CLR found that it was just an object[].

Do you expect every element in the array to already be a string? If so, you should just cast each element individually. If not, you'll have to add a call to ToString (or some other way of converting each element to a string) - but be careful of null values.

As an aside, empty catch blocks are a really bad idea. What do you really want to happen if something goes wrong? And what kind of errors do you want to handle in what way? Some errors to think about:

What if one of the keys is null?
What if you get duplicate keys?
What if the input array has an odd number of elements?

Finally, I'd suggest putting the i += 2 in the for loop "header" instead of at the end of the block.

answered Dec 31, 2009 at 8:38

Jon Skeet

1.5m893 gold badges9.3k silver badges9.3k bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

A9S6 Over a year ago

+1: This is my favorite question during an interview. People usually get confused between CONVERT and CAST

Silver Phoenix · Accepted Answer · 2009-12-31 08:08:29Z

1

Try the Array.ConvertAll method.

answered Dec 31, 2009 at 8:08

Silver Phoenix

5201 gold badge5 silver badges11 bronze badges

Comments

Red Swan · Accepted Answer · 2010-01-01 10:37:35Z

-1

See This is working: public Dictionary ArrayToDictionaryConverter(object [] objArray) { string[] strArray = Array.ConvertAll(objArray,Convert.ToString);
Dictionary dictionary = null; try { dictionary = new Dictionary(); for (int iVal = 0; iVal < strArray.Length; ) { dictionary.Add(strArray[iVal], strArray[iVal + 1]); iVal += 2; } } catch (Exception ex) { } return dictionary; }

answered Jan 1, 2010 at 10:37

Red Swan

15.6k44 gold badges163 silver badges241 bronze badges

1 Comment

PP. Over a year ago

-1 for using Convert.ToString when there's no such package Convert

Collectives™ on Stack Overflow

Unable to cast from object array to a string array

This is my function.

3 Answers 3

1 Comment

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

This is my function.

3 Answers 3

1 Comment

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related