Using a custom Linq Data Context with NULL DateTime field...?

Question

I have a custom DataContext with a Table member...

Entry is defined as...

[Table(Name="Entry")]
public class Entry
{
  [Column]
  public DateTime MyDate { get; set; }
}

The MyDate field in the Entry table can be NULL.

I have a very simple Linq query that retrieves all records in Entry but when it encounters a NULL MyDate field, I receive a System.InvalidOperationException error with the following details...

The null value cannot be assigned to a member with type System.DateTime which is a non-nullable value type.

Is there a way to set a default DateTime (with 0 ticks, for instance) when I encounter a NULL...?

Answer 1

If date is NULL in database, you shouldn't replace it with 0 in application. When you write 0 back to db, it will propably fail or just change value to invalid.

You can replace DateTime with DateTime?:

[Table(Name="Entry")]
public class Entry
{
[Column]
public DateTime? MyDate { get; set; }
} 

Adding ? makes property Nullable. Since it can be nullable in database, it should be nullable in your model.

Answer 2

My preferred approach is a nullable DateTime in this case:

[Column]
public DateTime? MyDate { get; set; }

Or:

public Nullable<DateTime> MyDate { get; set; }

Is that not an option?

Answer 3

Can you declare it as public DateTime? MyDate { get; set; }?

If you don't want it to actually ever be null, you can do this:

private DateTime _MyDate;
public DateTime? MyDate
{
    get { return _MyDate; }
    set { _MyDate = value.GetValueOrDefault(); }
}

This will give you 0 Ticks whenever the value in the DB is NULL.