比较Nullable DateTime变量的默认值

Question

In my C# code, I have a DateTime? variable. While getting the values from database it can be null or can have some date/time value.

On the front end side I don't want to get the default value (01-01-1900 12:00:00 am). Whats the best way to compare my date variable for this default date?

Answer 1

You can create a const:

static readonly DateTime DefaultDateTime = new DateTime(1900, 1, 1, 0, 0, 0);

and then compare this way:

DateTime? myVariable = returnedFromDb == DefaultDateTime ? default(DateTime?) : returnedFromDb;

Answer 2

You can have an extension method, something like this:

public static class DateTimeExtensions
{
    static DateTime SQL_DEFAULT = new DateTime(1900, 1, 1);

    public static bool IsDefaultValue(this DateTime dateTime)
    {
        return dateTime == SQL_DEFAULT;
    }
}

And then just test the value:

var isDefault = myDate.IsDefaultValue();