的DbContext - > DbSet - > Where子句缺失（实体框架6） [英] DbContext -> DbSet -> Where clause is missing (Entity Framework 6)

问题描述

我读过一些教程与实体框架6 ...

I've read some tutorials with entity framework 6...

基础知识很容易。

using (var context = new MyContext())
{
    User u = context.Users.Find(1);
}

但如何使用去哪儿或别的东西上了DbSet与用户

But how to use "Where" or something else on the "DbSet" with the users?

public class MyContext : DbContext
{
    public MyContext()
        : base("name=MyContext")
    {
        //this.Database.Log = Console.Write;
    }

    public virtual DbSet<User> Users { get; set; }
}

用户

Users

[Table("User")]
public class User : Base
{
    public Guid Id { get; set; }

    [StringLength(100)]
    public string Username { get; set; }
}

和那它不工作的问题。

string username = "Test";
using (var context = new MyContext())
{
    User u = from user in context.Users where user.Username == username select user;
}

错误：有没有查询的实现模式为源类型DbSet。 去哪儿是找不到的。也许引用或using指令System.Link'丢失。

Error: There was no implementation of the query pattern for source type 'DbSet'. 'Where' is not found. Maybe a reference or a using directive for 'System.Link' is missing.

如果我尝试自动完成有没有一个方法。

If i try to autocomplete the methods there are none.

<强>为什么它不工作？ （

//编辑：
添加System.Linq的到文件的顶部改变上述问题的功能，使我还没有一个问题了。

// Adding System.Linq to the top of the file changes the functions of the problem above so that i havent a problem anymore.

但是，为什么其中，现在是错的？

But why the where is wrong now?

The type "System.Linq.IQueryable<User>" cant converted into "User" explicit. There already exists an explicit conversion. (Possibly a cast is missing)

推荐答案

由于@Grant Winney和@Joe。

Thanks to @Grant Winney and @Joe.

添加使用System.Linq的; 来在那里我特林上面的代码固定的问题文件的命名空间/顶

Adding using System.Linq; to the namespace/top of the document where i'm tring the code above fixed the problem.

和使用线之上它为列表的第一个项目。

And using the line above it works for the first item of the list.

User user = (select user from context.Users where user.Username == username select user).First();

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