Should I use ToString() or GetDateTimeFormats() to format a DateTime?

Question

I know how to format a DateTime as a String. There may be many ways to format a DateTime as a String, and I have found few questions related to DateTime formatting.

But I found and tried two ways:

1. GetDateTimeFormats()
2. ToString("MM/dd/yyyy")

I tried this code:

public static class DateTimeFormates
{
    public static string FormatMyDate(this DateTime DT)
    {
        // My Actual Date Time Comes in this Format
        //8/23/2013 12:43:12 PM

        // I'm expecting Format like below

        String FormatWayOne = DT.GetDateTimeFormats()[3];
        //08/23/2013

        String FormatWayTwo = DT.ToString("MM/dd/yyyy");
        //08/23/2013

        return FormatWayOne;
    }
}

I have a Global class with Global method to format a DateTime as a String. But here what I want to know which method is the best practice so I can use it? The method is called all over the application.

Answer 1

GetDateTimeFormats is not a replacement for ToString and vice versa. If you know what format you want, there's no need to call GetDateTimeFormats. As well as it being clearer to use ToString, the document for GetDateTimeFormats states this (emphasis mine)

Because this method uses culture-sensitive data, you should not assume that multiple calls to the method will return identical data. The data returned by this method can change if the current culture changes, the user overrides individual cultural settings, or an update occurs to the system's cultural data.

This could potentially break your code as the third element could be something else when run in another culture.

By using ToString, you're avoiding having to loop through all date formats (hence being more efficient) and you're making it clearer as to what format you like whilst ensuring that the format returned is the one you want.