IEnumerable和console.writeline

Question

I have this simple code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data;
using System.Data.Entity;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            NuLabsEntities db = new NuLabsEntities();

            IEnumerable<company> companies = from cmp in db.company select cmp;

            foreach (var row in companies)
            {
                Console.WriteLine(companies);
                Console.ReadLine();
            }
        }     
    }
}

I know it's a basic question: I'm learning c#

But i don't understand why, after creating with ado.net an edmx file and try running this simple code it returns me the following query instead of the result of a list of rows of the company table:

SELECT
    [Extent1].[companyId] AS [companyId],
    [Extent1].[labirintoCodiceCliente] AS [labirintoCodiceCliente],
    [Extent1].[labirintoCodiceAteco2007] AS [labirintoCodiceAteco2007],
    [Extent1].[name] AS [name],
    [Extent1].[doc] AS [doc],
    [Extent1].[notes] AS [notes],
    [Extent1].[vatNumber] AS [vatNumber],
    [Extent1].[taxCode] AS [taxCode],
    [Extent1].[LabirintoFornitoreId] AS [LabirintoFornitoreId],
    [Extent1].[LabirintoCommercialistaId] AS [LabirintoCommercialistaId],
    [Extent1].[LabirintoConsulenteDelLavoroId] AS [LabirintoConsulenteDelLavoroId]
    FROM [dbo].[company] AS [Extent1]

Answer 1

我认为您应该传递行对象

Console.WriteLine(row);

Answer 2

Why?

Its because type of companies is System.Data.Entity.Infrastructure.DbQuery<Company> and the ToString() method of it returns the Query.

When you use Console.WriteLine(somthings) the ToString method of somethings will be used to output data, so you will receive the ToString result that is Query Text.

How can I retrevie values?

To get value of a field you can use Console.WriteLine(row.SomeField); in the loop to receive value of SomeField of row.

Note

Remember that Console.WriteLine(row); will output type of you company class and the output will be a class name for each row.

Answer 3

1. Console.WriteLine(companies); should be Console.WriteLine(row.blah);

2. You need to call .ToList() and then loop through the collection. Query is evaluated when you call ToList() .

With foreach that you have coded, you get each company into row. you can access properties of company from row .

Lets assume your comany's structure is this

public class company
{
   public int companyId {get;set;}
   public string companyName {get;set;}
}

Your code should be

foreach (var row in companies.ToList())
{
  Console.WriteLine("CompanyId:"+row.CompanyId.ToString());
  Console.WriteLine("CompanyName:"+row.CompanyName);
  Console.ReadLine();
}

Answer 4

You are printing the query itself, because companies contains the query.

What you want to do is, run the query (foreach will do), and iterate over the result-set (you are already doing it), and for each row in the result-set, print the details you want, like

foreach (var row in companies) //row is each row in result set of query companies
{
    Console.WriteLine(row.SomeProperty); //row, not companies
    Console.WriteLine(row.SomeOtherProperty);
    Console.ReadLine();
 }