c-treeDB API for C# - Developers Guide

Updating Existing Records

To update an existing record, you need to perform the following actions:

1. Read the record from disk by calling one of the CTRecord.First(), CTRecord.Last(), CTRecord.Next(), CTRecord.Prev(), CTRecord.SeekRecord(), CTRecord.Find() or CTRecord.FindTarget() methods.
2. Update one or more fields using SetFieldValue() or one of the deprecated CTRecord.SetFieldAs...() methods.
3. Write the record by calling CTRecord.Write().

// update the first record

ARecord.First();

// change the first field

ARecord.SetFieldAsString(0, "Joe Smith");

// write the record

try

{

ARecord.Write();

}

catch (CTException err)

{

Console.Write("Update record failed with error {0}\n", err.GetErrorCode());

}

A record is updated when the new record flag is cleared and the edited record flag is set. The new record flag is cleared when a record is read from disk and it indicates that this is an existing record.

If you read a record from disk, and without updating the record data, call CTRecord.Write(), no data record is written to disk, since the edited record flag is cleared.

A record update can be forced by setting the record edited flag with a call to CTRecord.SetEdited() method.

// force update of first record

ARecord.First();

// set the edited flag

ARecord.SetEdited(true);

// write the record

try

{

ARecord.Write();

}

catch (CTException err)

{

Console.Write("Update record failed with error {0}\n", err.GetErrorCode());

}

A record can be duplicated by reading it from disk, setting the edited record flag by calling CTRecord.SetEdited() setting the new record flag by calling CTRecord.SetNew(), and calling CTRecord.Write() to write it to disk. Please note that a record can only be duplicated if the table has no indexes with unique keys.

// duplicate the first record

ARecord.First();

// set the edited flag

ARecord.SetEdited(true);

// set the new record flag

ARecord.SetNew(true);

// write the record

try

{

ARecord.Write();

}

catch (CTException err)

{

Console.Write("Write record failed with error {0}\n", err.GetErrorCode());

}