LINQ2SQL获取随机记录

Question

I found this handy query;

SELECT TOP 1 * FROM Advertising ORDER BY NEWID()

but need to turn it into a LINQ query.

I tried doing something like;

var a = (from record in Advertising
        select record)

but can't figure out how to do the ordering so that a random record is returned.

Answer 1

It is probably easiest to just execute the command directly.

var a = ctx.ExecuteQuery<Advertising>("select top 1 * from Advertising order by NEWID()").First();

You could also do it with an sproc, or if you want a totally generic way to do it you can query the count, then generate a random number in that range and skip. (As others have noted while I was typing this)

Answer 2

This won't generate the SQL you're looking at, but should return a random result without having to retrieve all records:

Random r = new Random();
var record = r.Next(Advertising.Count());

var randomRecord = Advertising.Skip(record).FirstOrDefault(1);

Edit: It should also be more efficient than a random sort (unless SQL Server optimizes the sort away)

Edit 2: Take(1) should be FirstOrDefault() to return a record, instead of a list 1 record long.

Answer 3

here is my get random method

Public Shared Function GetSingleRandom(Of T)(ByVal target As IEnumerable(Of T)) As T
        Dim r As New Random(DateTime.Now.Millisecond)
        Dim position As Integer = r.Next(target.Count)
        Return target.ElementAt(position)
    End Function