Oracle Date Format for C#

Question

Hi friend

i am new and in my project i have use asp.net and oracle database,
when i have enter date in textbox like(9/11/2013 - month-date-year) and run into insert query.
it will give me a error like:(ORA-01843: not a valid month at System.Data.OracleClient.).

so please help me for that., 

Thanks