Hi Libu,

If you have visited  https://doc.openerp.com/6.1/developer/12_api/  - this link than you would have known that Odoo works on XML-RPC protocol for communication between client and server.

Therefore if you want to establish a communication between a '.NET' application and Odoo/OpenERP, you need make use of XML-RPC protocol. For achieving this you need to make use of library or dll in .NET application which makes XML-RPC communication possible, so there is a "dll" available "CookComputing.XmlRPCV2", which provides the api's to communicate on XML-RPC protocol with Odoo/OpenERP.

After including this dll in you project you can call the core ORM 'create, search,write.. ' etc. as well as other methods/functions of OpenERP.

To communicate with OpenERP you need to call the 'login' method of OpenERP, which allows to do the login under OpenERP using 'openerp credentials' from .NET application. See example       

 [XmlRpcMethod("login")]
 int login(string dbName, string dbUser, string dbPwd);

Now using this you will have to call the login method to get logged in into OpenERP. For calling other methods of OpenERP you need call the 'execute' methods of OpenERP. See example

[XmlRpcMethod("execute")]
int create(string dbName, int userId, string pwd, string model, string method, XmlRpcStruct fieldValues);

[XmlRpcMethod("execute")]
Object[] search(string dbName, int userId, string pwd, string model, string method, Object[] filters);

[XmlRpcMethod("execute")]
Object[] get_data(string dbName, int userId, string pwd, string model, string method, object[] ids);

So, this is the way how you communicate from a .NET application (web or desktop) to OpenERP.

You need to search for "CookComputing.XmlRPCV2" dll.