ORA-01425: escape character must be character string of length 1

The implementation of Contains() method in LINQ with Entity Framework ODP seems not working properly when handling System.String argument directly in certain situations, it will generate LIKE with ESCAPE '\' statement in PL/SQL query which will throw ORA-01425 error (as shown in similar issue here). To mitigate this behavior, just use Trim() inside Contains() method against string argument:

availableTasks.Where(task => task.Document.RegistrationNumber.Contains(searchkeyWord.Trim())                      || task.WorkflowNumber.Contains(searchkeyWord.Trim())                      || task.Description.Contains(searchkeyWord.Trim()));

The Trim() method will generate INSTR and TRIM statements (or LTRIM-RTRIM pairs) as replacement of LIKE with ESCAPE statements, as in example below:

SELECT <snip> FROM <snip> WHERE [condition] AND ((NVL(INSTR("Filter1"."RegistrationNumber", TRIM(:p__linq__9)), 0)) > 0) OR ((NVL(INSTR("Filter1"."WorkflowNumber", TRIM(:p__linq__10)), 0)) > 0)OR ((NVL(INSTR("Filter1"."Description", TRIM(:p__linq__11)), 0)) > 0)

By implementing INSTR with TRIM, the query will run smoothly when handling LINQ generated parameters (:p__linq__XX) containing System.String value.

The ESCAPE in the SQL statement you posted is fine - ESCAPE '\'

But this is the query text logged by LINQ

The best way to see the real query statement send to DB is to activate a 10046 trace.

 ALTER SESSION SET tracefile_identifier = escape; alter session set events '10046 trace name context forever, level 12';

in your connection and run the statement.

You will find a file such as xxx_ora_NNNN_ESCAPE.trc in the trace folde of the DB Server.

I suspect you will see a statement using something like

escape '\\'

We had the same problem

Resolved by changing parameter CURSOR_SHARING to EXACT