Creating User in CRM-2011 using C#

protected void Create_CRM_User(string domainname, string firstname, string lastname, string emailid, string contactnumber, ITracingService tracingService, IOrganizationService service)

        {            

            tracingService.Trace("Inside Create_CRM_User");

            const string BusinessUnitEntityName = "businessunit";

            const string BusinessUnitIdColumnName = "businessunitid";

            const string ParentBusinessUnitIdColumnName = "parentbusinessunitid";

            const string SystemUserEntityName = "systemuser";

            const string FirstNameColumnName = "firstname";

            const string DomainNameColumnName = "domainname";

            const string LastNameColumnName = "lastname";

            const string InternalEmailAddress = "internalemailaddress";

            const string TelephoneNumber = "address1_telephone1";

            Guid userId = Guid.Empty;

            QueryExpression businessUnitQuery = new QueryExpression

            {

                EntityName = BusinessUnitEntityName,

                ColumnSet = new Microsoft.Xrm.Sdk.Query.ColumnSet(BusinessUnitIdColumnName),

                Criteria =

                {

                    Conditions =

                    {

                        new ConditionExpression(ParentBusinessUnitIdColumnName,

                            ConditionOperator.Null)

                    }

                }

            };

            // Get the business unit id from the returned entity

            EntityCollection entities = service.RetrieveMultiple(businessUnitQuery);

            Guid defaultBusinessUnitId = entities[0].Id;

            string new_domainname = createuser_domain + domainname;

            //Populate an entity with data for a new system user.

            Entity entity = new Entity(SystemUserEntityName);

            entity.Attributes.Add(DomainNameColumnName, new_domainname);

            entity.Attributes.Add(FirstNameColumnName, firstname);

            entity.Attributes.Add(LastNameColumnName, lastname);

            entity.Attributes.Add(InternalEmailAddress, emailid);

            entity.Attributes.Add(TelephoneNumber, contactnumber);

           

            entity.Attributes.Add(BusinessUnitIdColumnName, new EntityReference

            {

                Id = defaultBusinessUnitId,

                Name = BusinessUnitEntityName,

                LogicalName = BusinessUnitEntityName

            });

            userId = service.Create(entity);

            string crm_successvar = "Created CRM User with GUID " + userId.ToString();

            tracingService.Trace(crm_successvar);

          

        }

This code is done by our senior Techincal Consultant Palani