"in oracle the data like this '????????'" - where? In a web interface? That does not mean that it is really wrong - could be an encoding problem of that web page.
Since you can insert the data from a commandline, the column definition is likely ok.
I'd change the C# code. Instead of concatenating the SQL query, use a parameterized query.
com.CommandText = "insert into DEPTS values(:param1, :param2)";
com.Parameters.AddWithValue(":param1", dept_cod_txt.Text);
com.Parameters.AddWithValue(":param2", dept_name_txt.Text);
com.ExecuteNonQuery();