如果你需要三个月的信件，请使用“MMM”

使用"MMMM"自定义格式说明符:

DateTime.Now.ToString("MMMM");

It's

DateTime.Now.ToString("MMMM");

有4个Ms。

它应该是DateTime。ToString("MMMM")

你不需要所有额外的Ms。

你可以像mservideo建议的那样做，甚至更好，使用这个重载来跟踪你的文化:

DateTime.Now.ToString("MMMM", CultureInfo.InvariantCulture);

DateTime birthDate = new DateTime(1981, 8, 9);
Console.WriteLine ("I was born on the {0}. of {1}, {2}.", birthDate.Day, birthDate.ToString("MMMM"), birthDate.Year);

/* The above code will say:
"I was born on the 9. of august, 1981."

"dd" converts to the day (01 thru 31).
"ddd" converts to 3-letter name of day (e.g. mon).
"dddd" converts to full name of day (e.g. monday).
"MMM" converts to 3-letter name of month (e.g. aug).
"MMMM" converts to full name of month (e.g. august).
"yyyy" converts to year.
*/