How can someone handle default datetime

Question

I have DAL where I convert database null value to their equivalent representation in C#. For example:

NULL for Numeric = 0
NULL for String = String.Empty
NULL for DateTime = "1/1/0001" (i.e. DateTime.MinValue)

The problem, for date, lies in the presentation layer, especially in GridViews. You cannot show 1/1/01 to users.

What I used to do is check if myDate.Year=1 or myDate.Year < AcceptedDate and display empty string, but seems to be extra effort unlike other types

Please am open to better approach. Thanks.

Answer 1

Use Nullable datatype to store null value.

DateTime? value = null;
int? myNullableInt = 1;
value = DateTime.Now;

How to check whether variable has value or null

if (value!=null)

String value can store null, so there is no diffrent datatype for string to store null.

string var;
if (var == null)

or

if (String.IsNullOrEmpty(var))

Answer 2

You can use Nullable DateTime, so you will return DateTime? instead of DateTime from your DAL. This way you can check if returned value is null.

DateTime? dateTime = null;

Answer 3

As the others mention, you could use a System::Nullable<DateTime>.

The other approach I've seen is to use a standard DateTime and just use a special value such as DateTime.MinValue. This is useful if you need to honor an existing interface's types and can't change the DateTime to a Nullable<DateTime>.

Answer 4

You can also use DateTime.MinValue constant.

http://msdn.microsoft.com/en-us/library/system.datetime.minvalue.aspx

Your conditions would be:

if (myDate == DateTime.MinValue)

Answer 5

You can either use a Nullable DateTime as the others suggested, or use this trick: (To prevent non valid defaults.)

// If dateTime has not been initialize, initialize to Now
// (or to any other legal inital values)
dateTime = ((dateTime != new DateTime()) ? dateTime : DateTime.Now);

This trick is useful if you have to use a non-nullable DateTime and want to provide a default if none. (E.g. you have a non-nullable DateTime column in a DB and want to set the value only if row is new.)

Answer 6

I don't think you have much choice but to make the check like you have been and display accordingly. A nullable type might make things easier for you. Depending on your data, even the numeric should be treated this way. DBNull != 0.