NHibernate - Why my DateTime property is always DateTime.MinValue

Question

Hello there,

I have a [DataContract] called ReportRequest with a NOT NULL column 'SubmittedAt'. So my DataContract looks something like:

[DataContract]
public class ReportRequest
{
    Int32 templateId;
    DateTime submittedAt = DateTime.Now;

    [DataMember]
    public virtual Int32? Id
    {
        get;
        set;
    }

    public virtual DateTime SubmittedAt
    {
        get {
              return submittedAt; 
        }
        set
        {
            submittedAt = value; 
        }
    }
}

Because, I have taken a private variable submittedAt and is initialised with DateTime.Now,

shouldn't the SubmittedAt property have the same value??

But when i am calling NHibernate

session.Save(objReportRequest);

I am getting the error:

SqlDateTime overflow. Must be between 1/1/1753 12:00:00 AM and 12/31/9999 11:59:59 PM.

Any thoughts why I am getting this error?

As a workaround for now I have changed getter for SubmittedAt property as:

        get {
            if (submittedAt == DateTime.MinValue)
                return DateTime.Now;
            else
                return submittedAt; 
        }

Answer 1

It's because DateTime.MinValue doesn't have the same meaning as the minimum value you could store in a SQL Server datetime column. In SQL server datetime column the minimum date you could store is the one you get in your exception stack. It is SqlDateTime.MinValue

Answer 2

SQL Server minimum DateTime value is bigger than DateTime.Min value. So you cannot save minimum value to database.

Answer 3

As Marek Tihkan already said: SqlServer can not store the DateTime.MinValue, it is outside of the value range of SqlServer's DateTime data type.

The best advise is to use nullable types anyway:

[DataContract]
public class ReportRequest
{
    DateTime? submittedAt = null;

    public virtual DateTime? SubmittedAt
    {
        get {
              return submittedAt; 
        }
        set
        {
            submittedAt = value; 
        }
    }
}

By SubmittedAt.HasValue you know if it is actually set to something reasonable. You shouldn't depend on some "magic values" to decide if a value is initialized or not.