DateTime.ToLongDateString

//引入命名空间
using System;
using System.Globalization;

class Sample 
{
    public static void Main() 
    {
        // Initialize a DateTime object.
        Console.WriteLine("Initialize the DateTime object to May 16, 2001 3:02:15 AM.
");
        DateTime dateAndTime = new System.DateTime(2001, 5, 16, 3, 2, 15);

        // Display the name of the current culture.
        Console.WriteLine($"Current culture: "{CultureInfo.CurrentCulture.Name}"
");
        var dtfi = CultureInfo.CurrentCulture.DateTimeFormat;

        // Display the long date pattern and string.
        Console.WriteLine($"Long date pattern: "{dtfi.LongDatePattern}"");
        Console.WriteLine($"Long date string:  "{dateAndTime.ToLongDateString()}"
");

        // Display the long time pattern and string.
        Console.WriteLine($"Long time pattern: "{dtfi.LongTimePattern}"");
        Console.WriteLine($"Long time string:  "{dateAndTime.ToLongTimeString()}"
");

        // Display the short date pattern and string.
        Console.WriteLine($"Short date pattern: "{dtfi.ShortDatePattern}"");
        Console.WriteLine($"Short date string:  "{dateAndTime.ToShortDateString()}"
");

        // Display the short time pattern and string.
        Console.WriteLine($"Short time pattern: "{dtfi.ShortTimePattern}"");
        Console.WriteLine($"Short time string:  "{dateAndTime.ToShortTimeString()}"
");
    }
}

Current culture: "en-US"

Long date pattern: "dddd, MMMM d, yyyy"
Long date string:  "Wednesday, May 16, 2001"

Long time pattern: "h:mm:ss tt"
Long time string:  "3:02:15 AM"

Short date pattern: "M/d/yyyy"
Short date string:  "5/16/2001"

Short time pattern: "h:mm tt"
Short time string:  "3:02 AM"

转载自：https://vimsky.com/examples/detail/csharp-method-system.datetime.tolongdatestring.html