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FieldNo

property FieldNo: Integer read;

Example​

function BackendOrdinal(const Data: TvxClientDataSet; const Name: string): Integer;
begin
  Result := Data.FieldByName(Name).FieldNo;
end;

Usage​

FieldNo returns the provider/backend field ordinal after object-field offset adjustment; it is not the zero-based Fields collection index.

  • Use FieldName for business mappings; treat this number as schema metadata for diagnostics.
  • Never assume it is zero-based, contiguous or stable across query/schema/provider changes.
  • Do not use it to index Fields; use Index or Fields[...] for collection position.

Additional Technical Info​

FieldNo identifies the field position used by the dataset/provider's low-level record APIs. It is distinct from Index.

Source-backed behaviour​

The getter begins with the internally assigned FFieldNo. For ordinary top-level, blob or non-data fields it returns that value. For a child data field it applies the field's own positive object offset, or walks parent object fields until it finds a positive offset and adds Parent.Offset * (Parent.Size + 1). This supports flattened/object-field layouts.

Client-dataset code passes this number to DSBase operations such as GetField, PutField and VerifyField; positive values are normally native stored-field ordinals. Calculated/lookup fields may have non-positive numbers. Reordering the public field collection with Index does not necessarily change FieldNo.

Official RTL references​

Created 2026-07-15