Try this:

ClassMethod GetTreeInfo(
  pRoot As %String,
  Output pTree,
  ByRef pParms) As %Status
{
  Set MyId=..GetId,pos=1
  &Sql(Select Name,ID into :name,:id from MSDS_COM.Loc where Parent=:MyId)
  Set:SQLCODE (name,id)=""
  if pRoot=""
  {
    Set pTree(0,"ch",1) = ""
    Set pTree(1) = $LB(name,id,1,"","")
  }
  Quit $$$OK
}

For further examples, see the class ZENTest.DynaTreeTest in the SAMPLES namespace.

Through %ZEN.proxyObject is unlikely to work, since the q parameter cannot be disabled in this case

q - output numeric values unquoted even when they come from a non-numeric property

Use your own class, for example:

Class dc.proxyObject Extends %RegisteredObject
{

Property ID As %VarString;

}

set object = ##class(dc.proxyObject).%New()
set object.ID = 123456

set x = ##class(%ZEN.Auxiliary.jsonProvider).%WriteJSONStreamFromObject(.json,object,,,,"aelotw")

Output:

{
  "ID":"123456"
}

I do not observe any differences in the behavior of xDBC and Portal.

Given:

Class dc.test Extends %Persistent
{

Property s1 As %String(MAXLEN = 2, TRUNCATE = 1);

Property s2 As %String(MAXLEN = 2);
}

• insert into dc.test(s1,s2)values('abc','ab')

  Result

  ID	s1	s2
  1	ab	ab

• insert into dc.test(s1,s2)values('abc','abc')

  Result for any JDBC/ODBC tools (DBVisualizer, SQL Data Lens, etc.):

  [SQLCODE: <-104>:<Field validation failed in INSERT>]
  <Field 'dc.test.s2' Truncation (Varchar Value: 'abc ...' Length: 3) > maxlen:  (2)>]

  Result for Management Portal:

  [SQLCODE: <-104>:<Field validation failed in INSERT>]
  
    [%msg: <Field 'dc.test.s2' (value 'abc') failed validation>]