SqlException was unhandled

请给我建议，我有代码，在执行过程中显示此异常：

SqlException未处理。无法绑定多部分标识符"T.TerritoryDescription"
无法绑定由多部分组成的标识符"T.TerritoryID"
无法绑定由多部分组成的标识符"T.TerritoryDescription"。

当我在ManagementStudio中运行SQL查询时，我会得到一些结果。当我在Visual Studio中使用此脚本运行代码时，我在这行代码上遇到异常

reader = command.ExecuteReader();

这是我的代码：

public void databaseQuestion()
{
    SqlConnection con = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["MyConnectionString"].ConnectionString);
    SqlCommand command = 
       new SqlCommand((@"select T.TerritoryID,T.TerritoryDescription,avg(O.Freight)
                         from Employees E
                         inner join EmployeeTerritories ET on E.EmployeeID = ET.EmployeeID
                         inner join Orders O on E.EmployeeID = O.EmployeeID
                         where T.TerritoryDescription ='Bedford'
                         group by T.TerritoryID,T.TerritoryDescription,O.Freight") ,con);
    dbFile = filePath + @"'sqlFile.txt";
    SqlDataReader reader;
    con.Open();
    reader = command.ExecuteReader();
    using (StreamWriter file = new StreamWriter(dbFile, false))
    {
        while (reader.Read())
        {
            file.WriteLine(reader["T.TerritoryID"] + "'t" + reader["T.TerritoryDescription"]+ "'t" +reader["O.Freight"]);
        }
    }
    reader.Close();
    con.Close();
}