Get a random row via EF

Question

I'm building an asp.net core webapp, and now I need to collect a random row from the database (sql) for posting in one of the views. Would very much appreciate any help I can get in doing and understanding this. Code, explanations, links to postings, enything is useful.

I don't fully understand how EF-asp.net core works, so that's what really makes it hard in searching for posts that are related to my problem.

Thank you in advance.

/Peter

Answer 1

Since you are using EF, I'll provide you with a LINQ-solution.

int total = context.YourEntities.Count();
Random r = new Random();
int offset = r.Next(0, total);

var result = context.YourEntities.Skip(offset).FirstOrDefault();

All this code does is get the total number of records, and generate a random number between [0, total). Note the boundary types: inclusive from the lower-end, exclusive from the upper-end.

You use this random number as an "offset", that is, how many records to skip ( .Skip(offset) ), and then retrieve the very first element of the remaining part of the sequence. If there are no records at all, FirstOrDefault returns null .

Answer 2

在 EF (EF Core) 中，您可以通过这种方式简单地使用 LINQ 语法（OrderBy 方法）：

context.MyEntities.OrderBy(r => Guid.NewGuid()).Take(10);