StrataFrame Forum » StrataFrame Application Framework - V1 » Business Objects and Data Access (How do I?) » Handling null value

Handling null value

Chan — Thu, 01 Feb 2007 08:48:22 GMT

Hi,
I have a table with 3 fields

[quote]Field Name Type ALlow NULL PK Indentity
---------------------------------------------------------------------
ID int No Yes Yes
Descr varchar(30) No No No
FKID int Yes No No

[/quote]

I set my BO to map to this table, set ID and Descr to Do Not Allow NULL; FKID to Use nullable generic in BO mapper allow null option. When I save new record, I found that FKID is always ZERO instead of NULL if I leave FKID blank (bound in combobox). I figured out that myBO.AllowNullValuesOnNewRow = false.

So, I try to set myBO.AllowNullValuesOnNewRow = true but then I will hit error complaint that system unable to convert DBNull to string for textbox. I was thinking to change "Descr" to use "Return alternate on null" option.

May I know is it the prefered way? Or, any recommendation?

Thank you

RE: Handling null value

StrataFrame Team — Thu, 01 Feb 2007 08:48:22 GMT

The CurrentRow property is a DataRow object reference, not a wrapper for a DataRow, and the DataRow class does not have GetXXX methods like the DbDataReader class does. Generating the code in the properties was the most efficient solution.

RE: Handling null value

Alexnaldo C Santos — Wed, 31 Jan 2007 19:48:19 GMT

Hi,

I think that is better change the code generate to, like it :

public string MyField
{
get {

return CurrentRow.GetString("myField");
}

set

{ CurrentRow["myField"] = value; }

}

The "CurrentRow" class must have GetXXXXX for each type, like GetInt(..), GetDate(...), so you can return values more easy, like "null".

Regards,
Alexnaldo Santos

RE: Handling null value

Trent L. Taylor — Tue, 30 Jan 2007 16:56:24 GMT

Strings do not support a nullable generic. You will have to use the "Return Alternate Value" option for a string. Generally when this is selected for a string, then you want to set the return value as "".