Изменение значений в базе данных

где то, так:

var query = $"UPDATE \"Object_nedvizimosti\" " +
                        $"SET \"status\" = :status" +
                        $"WHERE \"object_code\" = :object_code;";
var com = new NpgsqlCommand(query, con);
var status = comboBox_status.Text.Trim();
var object_code = comboBox_object_code.Text.Trim();
int object_code_integer;
bool success  = int.TryParse(object_code, out object_code_integer);
try
{
    com.Parameters.Add(new NpgsqlParameter("status", NpgsqlTypes.NpgsqlDbType.Text));
    com.Parameters.Add(new NpgsqlParameter("object_code", NpgsqlTypes.NpgsqlDbType.Text));
    com.Parameters[0].Value = status;
    if(success)
    {
       com.Parameters[1].Value = object_code_integer;
    }
    com.ExecuteNonQuery();
}
catch (NpgsqlException e) 
{ 
    Debug.WriteLine("Exception: " + e.Message + '\n');
}