Question

I have a class named project with the following data members.

class Project
{
    private int Record_Num;
    private int GCD_ID;
    private string Project_Desc;
    private string Proponent_Name;
    private string Station_ID;
    private string OpCentre;
    private string Sector_ID;
    private string PLZone;
    private string Feeder_ID;
    private string DxTx_ID;
    private string OpControl_ID;
    private string Type_ID;
    private string ConnKV_ID;
    private string Status_ID;
    private double MW;
    private string Subject;
    private int Ip_Num;
    private int H1N_ID;
    private int NOMS_Slip_Num;
    private DateTime NMS_Updated;
    private DateTime Received_Date;
    private Nullable<DateTime> Actual_IS_Date;
    private string Scheduled_IS_Date;
    private string UP_Station_ID;
    private string UP_Feeder_ID;
    private string HV_Circuit;
}

i query the database and retrieve the values through a data table which assigns the value to the project object like this.

for (int prjIdx = 0; prjIdx < dt.Rows.Count; prjIdx++)
            {
                newProject = new Project(Convert.ToInt32(dt.Rows[prjIdx]["RecordNum"].ToString()), Convert.ToInt32(dt.Rows[prjIdx]["GCDID"].ToString()),
                    dt.Rows[prjIdx]["ProjectDesc"].ToString(), dt.Rows[prjIdx]["ProponentName"].ToString(),
                    dt.Rows[prjIdx]["StationName"].ToString(), dt.Rows[prjIdx]["OpCentre"].ToString(),
                    dt.Rows[prjIdx]["SectorName"].ToString(), dt.Rows[prjIdx]["PLZone"].ToString(),
                    dt.Rows[prjIdx]["FeederDesc"].ToString(), dt.Rows[prjIdx]["DxTx"].ToString(),
                    dt.Rows[prjIdx]["OpControl"].ToString(), dt.Rows[prjIdx]["Type"].ToString(),
                    dt.Rows[prjIdx]["ConnectionKV"].ToString(), dt.Rows[prjIdx]["Status"].ToString(),
                    Convert.ToDouble(dt.Rows[prjIdx]["MW"]), dt.Rows[prjIdx]["Subject"].ToString(),
                    Convert.ToInt32(dt.Rows[prjIdx]["IpNum"]), Convert.ToInt32(dt.Rows[prjIdx]["H1NID"]),
                    Convert.ToInt32(dt.Rows[prjIdx]["NomsSlipNum"]),Convert.ToDateTime(dt.Rows[prjIdx]["NmsUpdated"]),
                    Convert.ToDateTime(dt.Rows[prjIdx]["ReceivedDate"]),Convert.ToDateTime(dt.Rows[prjIdx]["ActualIsDate"]),
                    dt.Rows[prjIdx]["ScheduledIsDate"].ToString(),dt.Rows[prjIdx]["UpStation"].ToString(),dt.Rows[prjIdx]["UpFeeder"].ToString(),
                    dt.Rows[prjIdx]["HVCircuit"].ToString());

                newProject.record_num = Convert.ToInt32(dt.Rows[prjIdx]["RecordNum"]);
                projList.Add(newProject);

            }

now my problem is, all the date time values retrieved from the database can be null.so if it encounters a null value, it fails to convert it and hence it cannot be assigned in to the object. thus it give me an error

how do i tackle the proble.
should i change the date time variable to string data type. but thats a lame solution. please help//

Answer 1

DateTime is a value-type, you could use the nullable datetime (DateTime?)

MSDN Ref on Nullable Structure

[...]
private int NOMS_Slip_Num;
private DateTime? NMS_Updated;
private DateTime? Received_Date;
private Nullable<DateTime> Actual_IS_Date;
[...]

Doing so will require changes in how you retrieve the value. One way to do so, would be to implement a null or DBNull check, and set the value of nullable datetimes in the Project instanciation using a ternary operator.

public static class Extensions
{
    public static bool IsNull(this object o)
    {
        if (o == null || DBNull.Value.Equals(o))
            return true;
        else
            return false;
    }
}

and use it like this in Project’s instanciation :

var receivedDate = dt.Rows[prjIdx]["ReceivedDate"];
var actualDate = dt.Rows[prjIdx]["ActualIsDate"];
newProject = new Project([...],
                       receivedDate.IsNull() ? null : Convert.ToDateTime(receivedDate),
                       actualDate.IsNull() ? null : Convert.ToDateTime(actualDate),
                       [...]);