Asp.net-Object reference not set to an instance of an object

public int Insert(string _Type, string _Name, string _Address, string Postal_Address, string _Phone, string _Fax)
       {
           SqlConnection con = new SqlConnection(constr);
           con.Open();
           SqlCommand cmd = new SqlCommand("usp_proc", con);
           cmd.CommandType = CommandType.StoredProcedure;
           try
           {
               string Docket_ID;
               cmd.Parameters.AddWithValue("@_Type", _Type);
               cmd.Parameters.AddWithValue("@_Name", _Name);
               cmd.Parameters.AddWithValue("@_Address", _Address);
               cmd.Parameters.AddWithValue("@Postal_Address", Postal_Address);
               cmd.Parameters.AddWithValue("@_Phone",_Phone);
               cmd.Parameters.AddWithValue("@_Fax", _Fax);
            ;

               SqlParameter p = new SqlParameter("@Emp_ID", SqlDbType.Int);
               p.Direction = ParameterDirection.Output;
               cmd.Parameters.Add(p);
               Emp_ID = p.Value.ToString();
               return cmd.ExecuteNonQuery();

           }
           catch
           {
               throw;
           }
           finally
           {
               cmd.Dispose();
               con.Close();
               con.Dispose();
           }
       }