How can I convert a string in the format “YYYYMM” to “MMMYY”?

问题

I want to pass values in YYYYMM format such as "201509" to a function and retrieve the human-friendlier "MMMYY" format, such as "Sep 2015".

I thought this might work:

internal static string GetMMMYYFromYYYYMM(String YYYYMMVal)
{
    string intermediateStr = YYYYMMVal + "01";
    DateTime intermediateDate = Convert.ToDateTime(intermediateStr);
    return intermediateDate.ToString("MMMyy");
}

...but no, it crashes with "String was not recognized as a valid DateTime"

ISTM that the YYYYMMDD format should be grokkable and convertible to a DateTime. What do I need to change?

UPDATE

Since I wasn't getting quite what I wanted, I decided to "brute force it" like so:

internal static string GetMMMYYFromYYYYMM(String YYYYMMVal)
{
    string yearAsTwoChars = YYYYMMVal.Substring(2, 2);
    string threeCharAbbreviation = YYYYMMVal.Substring(4, 2);
    if (threeCharAbbreviation.Equals("01"))
    {
        threeCharAbbreviation = "Jan";
    }
    else if (threeCharAbbreviation.Equals("02"))
    {
        threeCharAbbreviation = "Feb";
    }
    else if (threeCharAbbreviation.Equals("03"))
    {
        threeCharAbbreviation = "Mar";
    }
    else if (threeCharAbbreviation.Equals("04"))
    {
        threeCharAbbreviation = "Apr";
    }
    else if (threeCharAbbreviation.Equals("05"))
    {
        threeCharAbbreviation = "May";
    }
    else if (threeCharAbbreviation.Equals("06"))
    {
        threeCharAbbreviation = "Jun";
    }
    else if (threeCharAbbreviation.Equals("07"))
    {
        threeCharAbbreviation = "Jul";
    }
    else if (threeCharAbbreviation.Equals("08"))
    {
        threeCharAbbreviation = "Aug";
    }
    else if (threeCharAbbreviation.Equals("09"))
    {
        threeCharAbbreviation = "Sep";
    }
    else if (threeCharAbbreviation.Equals("10"))
    {
        threeCharAbbreviation = "Oct";
    }
    else if (threeCharAbbreviation.Equals("11"))
    {
        threeCharAbbreviation = "Nov";
    }
    else if (threeCharAbbreviation.Equals("12"))
    {
        threeCharAbbreviation = "Dec";
    }
    return string.Format("{0} {1}", threeCharAbbreviation, yearAsTwoChars);
}

...and, though it returns what I want "Sep 15", "Oct 15" etc., I still see "15-Sep" and "Oct-15" on my page...?!?

I'm calling that helper method like so:

var monthYearCell = _xlPivotDataSheet.Cells[_lastRowAddedPivotTableData + 1, 4];
monthYearCell.Value2 = ReportRunnerConstsAndUtils.GetMMMYYFromYYYYMM(MonthYear);

I reckon Excel must be "autocorrecting" behind the scenes or something; reminds me of a movie I saw ("Reds" maybe?) where the protagonist went semi-ballistic when his editor changed what he wrote. I often feel this way about Word and Excel. How can I tell Excel (assuming this is the problem) to just leave it alone - "What I have written, I have written"?

回答1:

You should use DateTime.ParseExact. So your code will look like this:

internal static string GetMMMYYFromYYYYMM(String YYYYMMVal)
{
    DateTime intermediateDate = DateTime.ParseExact(YYYYMMVal, "yyyyMM", CultureInfo.InvariantCulture);

    return intermediateDate.ToString("MMMyy");
}

回答2:

You could use switch-case instead of all those if-else blocks which would, imho, increase the readability. i.e.

switch (threeCharAbbreviation)
{
    case "01":
        threeCharAbbreviation = "Jan";
        break;
    case "02":
        //Etc.
    default:
        break;
}

And you can explicitly set format of cells in Excel. Haven't tested it myself but you can try the sample code below:

Excel.Range formatRange;
formatRange = xlWorkSheet.Range["A3", "B4"];
formatRange.NumberFormat = "MM-YY";

回答3:

try this

return DateTime.ParseExact(intermediateDate.ToString(), "yyyyMM", CultureInfo.InvariantCulture).ToString();

来源：https://stackoverflow.com/questions/40045761/how-can-i-convert-a-string-in-the-format-yyyymm-to-mmmyy

标签

datetime

datetime-format

date-conversion