Developers Guide

it might occur if your have added a table in entity designer who does not contain any primary key or related issue. go to entity designer, check your newly inserted table and save.

goto command prompt type sqlplus Enter user-name:   system Enter password:   <password-for-system> Create the user. For example, enter a statement in the following form: SQL> create user chris identified by <password-for-chris> ; Grant the user the necessary privileges. For example: SQL> grant CREATE SESSION, ALTER SESSION, CREATE DATABASE LINK, - CREATE MATERIALIZED VIEW, CREATE PROCEDURE, CREATE PUBLIC SYNONYM, - CREATE ROLE, CREATE SEQUENCE, CREATE SYNONYM, CREATE TABLE, - CREATE TRIGGER, CREATE TYPE, CREATE VIEW, UNLIMITED TABLESPACE - to chris; Optionally, exit SQL*Plus (which also closes the command window): SQL> exit

go to command prompt. type sqlplus / as sysdba SQL> alter user system identified by new_password_here;

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var result = from p in _context.ParentTable join c1 in _context.ChildTable1 on p.ID equals c1.ID into pc1Table from pc1Join in pc1Table.DefaultIfEmpty() join c2 in _context.ChildTable2 on p.ID equals c2.ID into pc2Table from pc2Join in pc2Table.DefaultIfEmpty() where (c1.columnname == "value1" || c2.columnname == "value2") && p.columnname == "value" select new { pID = p.ID, c1ID = c1.ID, c2ID = c2.ID};

On 64-bit Windows and 64-bit Office (2010, 2013) environments, there are many reports on this error. The fix or workaround is a bit strange but seems to work for most people out there. The " Microsoft Access Database Engine 2010 Redistributable " installation package seems the natural one to use but if it does not work then try second method. Using the " 2007 Office System Driver: Data Connectivity Components " to solve the above problem.