I'm new to programming and trying to do an exercise that formats a date to the Thai culture in a variety of formats this is what I have for my code so far:

    public String[] FormatAsSpecified(DateTime theDate, String theCulture, String[] formats)
    {
        String[] dateResults = new String[formats.Length];

        CultureInfo culture = CultureInfo.GetCultureInfo(theCulture);

        for (int i = 0; i < formats.Length; i++)
        {
            String culture_formatted_date = theDate.ToString(formats[i], culture);
            dateResults[i] = culture_formatted_date;
        }

        return dateResults;
    }

This is the test method that goes with it:

    [TestMethod]
    public void FormatAsSpecifiedReturnsDateLiteralsInSpecifiedFormatForAllStandardFormatStrings()
    {
        //Arrange
        var controller = new DateController();

        var theDate = new DateTime(2014, 2, 14, 9, 15, 32, 376);
        String theCulture = "th-TH";
        // Array of all supported standard date and time format specifiers.
        String[] formats
            = { "d", "D", "f", "F", "g", "G", "m", "o", "r", "s", "t", "T", "u", "U", "Y" };
        //Corresponding date literals for the standard Thai regional settings
        String[] expectedResults
            = {"14/2/2557"
                , "14 ?????????? 2557"
                , "14 ?????????? 2557 9:15"
                , "14 ?????????? 2557 9:15:32"
                , "14/2/2557 9:15"
                , "14/2/2557 9:15:32"
                , "14 ??????????"
                , "2014-02-14T09:15:32.3760000"
                , "Fri, 14 Feb 2014 09:15:32 GMT" 
                , "2014-02-14T09:15:32"
                , "9:15"
                , "9:15:32"
                , "2014-02-14 09:15:32Z"
                , "??????????? 14 ?????????? 2014 9:15:32"
                , "?????????? 2557"};

        //Act
        String[] actualResults = new String[15];
        for (int i = 0; i < formats.Length; i++)
        {
            actualResults[i]
                = controller.FormatAsSpecified(theDate, theCulture, formats[i]);
        }

        //Assert
        CollectionAssert.AreEqual(expectedResults, actualResults);
    }

I get an error in the test method at 'controller.FormatAsSpecified(theDate, theCulture, formats[i]);' that says "Argument 3, cannot convert from 'string' to 'string[]'" What am I doing wrong?