"Properties of Nullable DataColumns

Thedata column that feeds a business object property might allow null values. Theorder's [ShipDate] won't have a value until the order is shipped so thedatabase datetime column for the ship date allowsnulls.

However,the .NET DateTime type is a value type. It can't benull. Only reference types can be null. Which means the order propertycorresponding to the ship date cannot be a DateTime type.

Thiswas a serious problem in .NET 1.1. The predecessor to DevForce worked aroundthat problem. The Object Mapper made the property an Objecttypeand marked the property with an attribute that said it was a date.Unfortunately, it takes reflection to read an attribute. Developers had towrite guard code to watch out for nulls and to make sure no one tried to setthe ship date with something awful – like a string.

.NET 2.0 introduced nullable types.Now our programs can tell that ShipDateissupposed to be a DateTime andensure at compile time that its value is either null or a DateTime. Our code iscleaner, clearer, and more testable which means it can be more reliable."

    /// <summary>Gets or sets the ActivityDate.</summary>    [DBDataType(typeof(System.DateTime))]    public virtual Object ActivityDate {      get {         Object result_;        if (GetInterceptor<Object>("ActivityDate", GetActivityDateImpl, out result_)) return result_;        return GetActivityDateImpl();      }      set {           if (!SetInterceptor<Object>("ActivityDate", value, SetActivityDateImpl)) {             SetActivityDateImpl(value);          }      }        }    private Object GetActivityDateImpl() {      return GetColumnValue(ActivityDateColumn, typeof(System.DateTime), true);     }    private void SetActivityDateImpl(Object value) {      SetColumnValue(ActivityDateColumn, value);    }

    /// <summary>Gets or sets the DeletedDateTime.</summary>    [DBDataType(typeof(System.DateTime))]    public virtual System.DateTime DeletedDateTime {      get {         System.DateTime result_;        if (GetInterceptor<System.DateTime>("DeletedDateTime", GetDeletedDateTimeImpl, out result_)) return result_;        return GetDeletedDateTimeImpl();      }      set {           if (!SetInterceptor<System.DateTime>("DeletedDateTime", value, SetDeletedDateTimeImpl)) {            SetDeletedDateTimeImpl(value);          }        }        }    private System.DateTime GetDeletedDateTimeImpl() {      return (System.DateTime) GetColumnValue(DeletedDateTimeColumn, typeof(System.DateTime), false);     }    private void SetDeletedDateTimeImpl(System.DateTime value) {      SetColumnValue(DeletedDateTimeColumn, value);    }