将查询从SQL转换为LINQ

Question

I need to convert this SQL query to LINQ:

SELECT COUNT(result1.Id) AS total, 
    result1.OccurrenceDate, 
    result1.Path, 
    result1.Message, 
    result1.StackTrace 
FROM (SELECT * FROM tbllog ORDER BY OccurrenceDate DESC) AS result1
GROUP BY result1.Path, result1.Message ORDER BY total DESC

But I'm not getting success. I've tried in so many ways, nothing works. Some help?

Answer 1

Create a linq query out of the following:

SELECT * FROM tbllog ORDER BY OccurrenceDate DESC AS result1
GROUP BY result1.Path, result1.Message ORDER BY total DESC

Once that is done, write some linq to get your counts.

Answer 2

var results = _dbContext.tbllog
    .GroupBy( t => new { t.Path, t.Message })
    .Select( g => new 
        {
            Total = g.Count(),
            Path = g.Key.Path,
            Message = g.Key.Message
        }).OrderBy(p => p.Total);

It is worth to mention that your sql query is invalid because the properties OccurrenceDate and StackTrace is not in the GROUP BY clause nor with in an aggregate function, therefore it is invalid query. The same with the LINQ query. You should determine what you want to do with them. Either include them in the group by or use an aggregate function to select the appropriate value for each group.

Answer 3

I don't know what the context is for your question, but if you don't need to modify the query such that it executes with additional parameters, I would highly recommend executing the query as SQL. This is supported on all the ORMs that I am aware of (Entity Framework, NHiberate, LINQ to SQL, etc).

Erick