Question

I couldn’t find best solution when DateTime value is NULL.

I use this techinque When binding;

_ACTIVATION_DATE = dt.Rows[0]["ACTIVATION_DATE"] == DBNull.Value ? new DateTime(1970, 12, 30) : (DateTime?)dt.Rows[0]["ACTIVATION_DATE"];

When Inserting;

public void Insert()
{
    string ad="";
    string dd="";

    if (ACTIVATION_DATE == null)
        ad = "null";
    else
        ad = "'" + ACTIVATION_DATE + "'";
    if (DEACTIVATION_DATE == null)
        dd = "null";
    else
        dd = "'" +DEACTIVATION_DATE +"'";

    string sSQL = "INSERT INTO LINE_INFO (ACTIVATION_DATE,DEACTIVATION_DATE,STATUS,PO,NOTES) VALUES (" + ad + "," + dd + "," + _STATUS.ToString() + "," + _PO.ToString() + ",'" + _NOTES.ToString() + "');SELECT @@IDENTITY AS LASTID";
    }

Variables;

DateTime? ACTIVATION_DATE;
DateTime? DEACTIVATION_DATE;

What is the smart way to handle Null DateTime values?

When I find the solution I will write an article about this topic.

Answer 1

Why are you using new DateTime(1970, 12, 30) when you’re already using a nullable DateTime? The whole point of nullable value types is that you don’t need magic values like that.

I would possibly use:

_ACTIVATION_DATE = dt.Rows[0]["ACTIVATION_DATE"] as DateTime?;

That will automatically use the null value for any non-DateTime value. Of course, that means you’ll get a null value instead of an exception if you accidentally have an integer or something like that. Alternatively:

object tmp = dt.Rows[0]["ACTIVATION_DATE"];
_ACTIVATION_DATE = tmp is DbNull ? null : (DateTime?) tmp;

Then for the insert statement, do not include values directly in your SQL. Use a parameterized insert statement, and then you can just use a null DateTime? value to insert a null value. No need to mess around with string formats.