Migrating from .NET Core 2.2 to .NET Core 3.1 - In LINQ DefaultIfEmpty() does not translate Issue-CodePudding

I have following code in .NET CORE 2.2. It does not works in .NET 3.1. According to This article it says DefaultIfEmpty().Take(1) will not translate to SQL.

from students in Students.Where(e => e.StudentType == studentType)
join courseDetails in Course.Where(x => x.IsActive == true)
on students.CourseId equals courseDetails.Id into studentCourse
from courseDetails in studentCourse.DefaultIfEmpty().Take(1)
select new { students, courseDetails };

When I ran above LINQ statement I got following error.

'NavigationExpandingExpressionVisitor' failed. This may indicate either a bug or a limitation in EF Core. See https://go.microsoft.com/fwlink/?linkid=2101433 for more detailed information.",

PS: As per the requirement I must use Take(1). Because for each record in left side table right side can have multiple records.from that we will take only 1 record.

can anyone share suggestion to do it without breaking the LINQ Query

CodePudding user response：

I never do that in that way, I every time use First OR Default

from students in Students.Where(e => e.StudentType == studentType)
join courseDetails in Course.Where(x => x.IsActive == true)
on students.CourseId equals courseDetails.Id into studentCourse
from courseDetails in studentCourse.FirstOrDefault()
select new { students, courseDetails };

CodePudding user response：

Try next:

var query = from students in Students.AsQueryable().Where(e => e.StudentType == studentType)
    from courseDetails in Course.AsQueryable()
        .Where(x => x.IsActive == true)
        .Where(cd => cd.Id == students.CourseId)
        .Take(1)
        .DefaultIfEmpty()        
    select new { students, sc = courseDetails };

I don't have 3.1 installed on my machine, but 5.0 seems to translate it correctly.