Question

我有这个简单的代码：

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();
            }
        }     
    }
}

我知道这是一个基本问题：我正在学习c＃

但我不明白为什么在使用ado.net创建edmx文件并尝试运行这个简单的代码后，它会返回以下查询而不是公司表的行列表的结果：

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

我认为你应该传递行对象

Console.WriteLine(row);

Answer 2

<强>为什么吗

因为公司类型为System.Data.Entity.Infrastructure.DbQuery<Company>，而ToString()方法会返回查询。

当您使用Console.WriteLine(somthings)时，某些事件的ToString方法将用于输出数据，因此您将收到ToString结果，即查询文字。

我如何撤回价值？

要获取字段的值，您可以在循环中使用Console.WriteLine(row.SomeField);来接收SomeField行的值。

注意

请记住，Console.WriteLine(row);将输出您公司类的类型，输出将是每行的类名。

Answer 3

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您需要调用Console.WriteLine(row.blah);然后循环访问该集合。当您致电.ToList()时，会评估查询。

对于您已编码的ToList()，您会将每个foreach放入行中。您可以从company访问company的媒体资源。

让我们假设您的公司结构是

row

您的代码应为

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

Answer 4

您正在打印查询本身，因为companies包含查询。

你想要做的是，运行查询（foreach会这样做），迭代结果集（你已经在做了），对于结果集中的每一行，打印你想要的细节，像

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();
 }

IEnumerable和console.writeline

4 个答案: