from c in db.Clients
where c.Rate < 5
select c.Id;

S>from c in db.Clients
S>where c.Rate < 5
S>select c.Id;
S>

db.Clients 
|> Seq.filter (fun c -> c.Rate < 5)
|> Seq.map (fun c -> c.Id)

void main()
{
    import std.stdio : writefln;
    // An associative array mapping pairs of characters to integers
    int[char[2]] aa;
    auto arr = "ABBBA";

    // Iterate over all pairs in the string
    // ['A', 'B'], ['B', 'B'], ..., ['B', 'A']
    foreach (i; 0 .. arr.length - 1)
    {
        // String slicing doesn't allocate a copy
        char[2] pair = arr[i .. i + 2];
        // count occurrences
        aa[pair]++;
    }
    foreach (key, value; aa)
        writefln("key: %s, value: %d", key, value);
}

from c in db.Clients
where c.Rate < 5
select c.Id;

from c in db.Clients
where c.Rate < 5
select c.Id;

Р>>db.Clients 
Р>>|> Seq.filter (fun c -> c.Rate < 5)
Р>>|> Seq.map (fun c -> c.Id)
Р>>

query {
        for customer in db.Customers do
            select customer
    }

Р>>ничего оно компилятором не контролируется. Каждый день ef core падает в рантайме

string GetCaption(Item item) => item.Caption;
db.Items.Select(item => GetCaption(item)).FirstOrDefault()

Р>>ничего оно компилятором не контролируется. Каждый день ef core падает в рантайме

System.InvalidOperationException: "The LINQ expression 'DbSet<Article>()
    .Count(a => a.UpdateTime < a.ProcessingTime.GetValueOrDefault(01.01.0001 0:00:00 +00:00))' could not be translated.
 Additional information: Translation of method 'System.DateTimeOffset?.GetValueOrDefault' failed. 
If this method can be mapped to your custom function, see https://go.microsoft.com/fwlink/?linkid=2132413 for more information. 
Either rewrite the query in a form that can be translated, 
or switch to client evaluation explicitly by inserting a call to 'AsEnumerable', 'AsAsyncEnumerable', 'ToList', or 'ToListAsync'. 
See https://go.microsoft.com/fwlink/?linkid=2101038 for more information."

Р>>>ничего оно компилятором не контролируется. Каждый день ef core падает в рантайме

Р>System.InvalidOperationException: "The LINQ expression 'DbSet<Article>()
Р>    .Count(a => a.UpdateTime < a.ProcessingTime.GetValueOrDefault(01.01.0001 0:00:00 +00:00))' could not be translated.
Р> Additional information: Translation of method 'System.DateTimeOffset?.GetValueOrDefault' failed. 
Р>If this method can be mapped to your custom function, see https://go.microsoft.com/fwlink/?linkid=2132413 for more information. 
Р>Either rewrite the query in a form that can be translated, 
Р>or switch to client evaluation explicitly by inserting a call to 'AsEnumerable', 'AsAsyncEnumerable', 'ToList', or 'ToListAsync'. 
Р>See https://go.microsoft.com/fwlink/?linkid=2101038 for more information."

Р>

.Count(a => a.UpdateTime < a.ProcessingTime)