实体框架列投影

Question

I have this model:

public partial class SystemUser
{
    [Display(Name = "User")]
    public string Username { get; set; }
    [Display(Name = "Pass")]
    public string Password { get; set; }
    [Display(Name = "Admin")]
    public Nullable<bool> Type { get; set; }

}

this function return all record of SystemUser:

    public IEnumerable<object> GetAll()
    {
        var Users = Ctx.SystemUsers.ToList().Select(u => new SystemUser
        {
            Username = u.Username,
            Type = u.Type
        });

        return Users.ToList();
    }

but this query also have password column I dont need this.how can i remove this column from query? i dont want use anonymus type because it remove dataannotation

Answer 1

You should return Anonymous Types in GetAll() method. Change GetAll like this:

public IEnumerable<object> GetAll()
{
    var Users = Ctx.SystemUsers.ToList().Select(u => new
    {
        User = u.Username,
        Admin = u.Type
    });

    return Users.ToList();
}

Answer 2

No way of doing this without raw sql. You always fetch entire table row with Entity Framework.

Answer 3

Try this:

public IEnumerable<object> GetAll()
{
    return Ctx.SystemUsers.Select(u => new 
    {
        Username = u.Username,
        Type = u.Type
    }).ToList();
}

Answer 4

You can use a DTO and AutoMapper Queryable Extensions to support this scenario:-

public class SystemUserDto
{
  [Display(Name = "User")]
  public string Username { get; set; }

  [Display(Name = "Admin")]
  public Nullable<bool> Type { get; set; }
}

...

Mapper.CreateMap<SystemUser, SystemUserDto>();

...

public IEnumerable<SystemUserDto> GetAll()
{
    var Users = Ctx.SystemUsers.Project().To<SystemUserDto>();
}

Answer 5

Based on an unnecessarily involved exchange of comments across more than one question, it sounds like what you're really asking is:

I have a type which includes a Password field, which I get from the database with Entity Framework. This type includes data annotations which I need to use in an auto-generated UI. I have no control over the UI. How can I provide the UI with a type which includes these data annotations, but doesn't include the Password field?

In that case, define another type:

public class SystemUserViewModel
{
    [Display(Name = "User")]
    public string Username { get; set; }
    [Display(Name = "Admin")]
    public Nullable<bool> Type { get; set; }
}

And transform to that type:

Ctx.SystemUsers.ToList().Select(u => new SystemUserViewModel
{
    Username = u.Username,
    Type = u.Type
});

If you use an anonymous object, you don't have a class definition so you don't have any attributes (data annotations). If you use your SystemUser type then you have a Password property. To use something which is neither of these things, you have to define a type.