ASP.NET MVC从EF中的表获取特定列

Question

I have a table with below columns.

CREATE TABLE [dbo].[tbl_QuizQue](
    [id] [int] IDENTITY(1,1) NOT NULL,
    [question] [nvarchar](max) NOT NULL,
    [opt1] [nvarchar](50) NOT NULL,
    [opt2] [nvarchar](50) NOT NULL,
    [opt3] [nvarchar](50) NOT NULL,
    [ans] [nvarchar](50) NOT NULL
    )

I am trying to get a random record from this table, but only specific columns Like id, question, opt1, opt2, opt3. Present I am getting random record but it is fetching all columns. I tried below code for fetching a record with specific columns

dbUserEntities obj = new dbUserEntities();
    // GET api/values
    public IEnumerable<tbl_QuizQue> Get()
    {
        var result = obj.tbl_QuizQue.OrderBy(r => Guid.NewGuid()).Select(o => new { o.id, o.question, o.opt1, o.opt2, o.opt3 });
        return result;
        }

Here, i am getting below error while return result;

Cannot implicitly convert type 'System.Linq.IQueryable<AnonymousType#1>' to 
        'System.Collections.Generic.IEnumerable<studentQuiz.tbl_QuizQue>'. An explicit conversion exists (are you missing a cast?)

Help me where I am doing wrong.

Answer 1

I'd do this:

public IEnumerable<tbl_QuizQue> Get()
{
    var result = obj.tbl_QuizQue.OrderBy(r => Guid.NewGuid())
        .Select(o => new { o.id, o.question, o.opt1, o.opt2, o.opt3 })
        .AsEnumerable()
        .Select(q => new tblQuizQue {q.id, q.question, q.opt1, q.opt2, q.opt3);
    return result;
}

By first getting back just the columns you are interested in, you can constrain the query. You can then map them into the object you are interested in.

Answer 2

Change the return type of the Get function to

IEnumerable<dynamic>

and your code will execute.

As for whether it's a good idea, I guess you have to defer to the customs of the c# tribe.

I'd be tempted to use it all the time.