Conflict between NULL value in a DB and DateTime attributes

Question

I have a class with a field named myDateTime typed as nullable DateTime, these are the accessor methods:

System.DateTime? _MyDateTime;
public System.DateTime? MyDateTime {get; set;}

Somewhere else in my code I need to value MyDateTime attribute with the data write inside myColumn.

MyDateTime = Convert.ToDateTime(myReader["myColumn"]);

The value from myColumn can be NULL or DateTime. Alas if myColumn is NULL this code produce an error cause I can't convert a NULL value. Further, I can't write:

MyDateTime = System.DBNull.Value;

So I don't know how I could handle this issue if NULL value is present in that field. I would avoid the use of a simple object to store the data and I would preserve a sort of attributes typing.

Answer 1

You need to convert from DBNull.Value to the null value of DateTime?. It may be simplest to write an extension method on DbDataReader for that:

public static DateTime? GetNullableDateTime(this DbDataReader reader,
                                            string column)
{
    object value = reader[column];
    return value == DBNull.Value ? (DateTime?) null : (DateTime) value;
}

Then use it as:

MyDateTime = myReader.GetNullableDateTime("myColumn");

Note that I'm using a cast rather than Convert.ToDateTime - you could use the latter if you really want to automatically convert from strings to DateTime values etc, but I prefer to be a bit more explicit about that sort of thing. (It's a sign of the schema probably being inappropriate...)

Answer 2

You can use Tryparse as following...

System.DateTime? _MyDateTime;
public System.DateTime? MyDateTime {get; set;}
        if (DateTime.TryParse(myReader["myColumn"], out MyDateTime ))
        {
            //do stuffs if value is parsed successfully
        }
        else
        {

        }