InvalidOperationException
The command is in an invalid state. Either the ULCommand.Connection is missing or closed, the ULCommand.Transaction
value does not match the current transaction state of the connection, or the ULCommand.CommandText is invalid.
The statement is the current ULCommand object, with the ULCommand.CommandText and any ULCommand.Parameters as required.
If this method is called on a query that returns multiple rows and columns, only the first column of the first row is returned.
If the ULCommand.CommandType is System.Data.CommandType.TableDirect, ExecuteScalar performs an ULCommand.ExecuteTable() and
returns the first column of the first row.
SELECT statements are marked as read-only by default for performance reasons. If the query is going to be used to make updates,
the statement must end with " FOR UPDATE".