SetNull Method

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This method allows loading a null value in an attribute, and enables independence from the Generate null for nullvalue() property used in assigning a null value attribute.

Syntax

attribute.SetNull()

Description

If the attribute allows nulls in the table, using this method can force the attribute to take the null value.

The SetNull method is applied as follows:

  • Attributes. The attribute must accept nulls (Nullable property = Yes)
  • Variables based on BC. The associated attribute must accept nulls (Nullable property = Yes)
  • Variables based on SDT, for example, to stop recursion.

Examples

Case to Recursive SDTs:

If you define an 'Employee' SDT with a 'Manager' member of the type 'Employee', to stop recursion you have to program &Person.Manager.SetNull().

Before referring to the manager, ask if &Employee.Manager.Isnull(). If you do not program this line, the Manager is automatically initiated.

Employee SDT

&Employee.Id = 99
&Employee.Name = 'Mary Shelley'
&Employee.Manager.Id  = 69
&Employee.Manager.Name  = 'Er'
&Employee.Manager.Manager.SetNull()
&Employee.ToXML()

Programming is the same as in previous versions, plus IsNull() and SetNull() handling.

The result is the following:

<Employee>
</Employee>
Other examples:
OwnerCel.SetNull() if OwnerName.IsEmpty();
If Y.IsNull()
   X.SetNull()
Else
   X = Y
EndIf

Scope

Objects: Procedures, Transactions, Web Panels
Languages: .NET, Java, Ruby (up to GeneXus X Evolution 3), RPG, Visual FoxPro (up to GeneXus X Evolution 3), Cobol

See Also

Null Function
IsNull Function