TBlobField Class

TBlobField represents a field in a dataset that holds a reference to a binary large object (BLOB).

Pascal

TBlobField = class(TField);

C++

class TBlobField : public TField;

File

Description

TBlobField encapsulates the fundamental behavior common to binary large object (BLOB) fields. BLOB fields are database fields that contain raw binary data of arbitrary length. BLOB fields can represent different arbitrarily large data types. These data types are distinguished in the header of the binary data.

In addition to the field types supported directly, TBlobField is the direct ancestor of two BLOB field components: TMemoField (ftMemo) and TGraphicField (ftGraphic). These descendants represent BLOB fields that have headers peculiar to memos or graphic data, respectively.

TBlobField introduces new methods to support streaming data to and from the BLOB field and to support copying raw binary data between the BLOB field and a binary file. You can also use the stream returned by a dataset's CreateBlobStream method to read or write the data managed by a BLOB field.

If you use the Fields editor at design time to create a persistent field component for the BLOB field, you can access it by name at runtime. When using dynamic field components, you can access the TBlobField instance using the dataset's Fields property or FieldByName method.