using System;

using System.Globalization;

        using System.Text;

​

public class Program

{

    public static void Main()

    {

        string[] param = new string[] {null, "ABC"};

        var castedParam = param as Array;

        var result = ArrayToCsv(castedParam);

        Console.WriteLine(result);

    }

    protected static string ArrayToCsv( Array input )

        {

            if ( input == null ) return null;

​

            var result = new StringBuilder();

            var separator = ",";

            var quoted = false;

            if ( input is string[] )

            {

                separator = "\",\"";

                result.Append( '"' );

                quoted = true;

            }

​

            for ( var i = 0; i < input.Length; ++i )

            {

                if ( i > 0 ) result.Append( separator );

                var value = input.GetValue( i );

                result.AppendFormat( Convert.ToString( value, CultureInfo.InvariantCulture ) );

            }

​

            if ( quoted ) result.Append( '"' );

            return result.ToString();

        }

​

}