How does one reliably check if a nullable property contains no data? DBNull is killing me

I've begun using Massive, by Rob Conery. Awesome lit开发者_如何学Gotle "ORM" and very performant. However, I'm running into issues with System.DBNull comparisons on my nullable fields.

For example, I want to check if a property matches another property (in this example, a long type)

if (obj.MemberId == otherObj.MemberId) return true;

throws exception: Operator '==' cannot be applied to operands of type 'System.DBNull' and 'long'. In this case, obj.MemberId was null (more specifically, DBNull).

Ok, so I check if it's DBNull.Value first right? Like this:

if (obj.MemberId != DBNull.Value)
    return obj.MemberId == otherObj.MemberId;

Cool, that works, at least while obj.MemberId is DBNull, but when it's not (contains a long), another exception: Operator '!=' cannot be applied to operands of type 'long' and 'System.DBNull'.

DBNull is killing me. How does one reliably check if a nullable property contains no data?

Did you tried by using is operator?

if (obj.MemberId is DBNull)
{
    // it is null
    return false;
}
else
{
    // has some value
    return obj.MemberId == otherObj.MemberId;
}

Just using Convert.IsDBNull should do.

http://msdn.microsoft.com/en-us/library/system.convert.isdbnull(v=VS.90).aspx

if (!DBNull.Value.Equals(obj.MemberID) && obj.MemberID !=null && obj !=null)

or

if (!DBNull.Value.Equals(obj) && obj.MemberID !=null && obj !=null)

Select whatever applies to your case. This will give you a full proof check.

try this. this works for me;

string test = DBNull.Value.Equals(obj.Qty) ? string.Empty : obj.Qty.ToString();