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Calculating rank in EF Core 6?

I have a table in which I want to calculate the rank of my data based on Amount.
var result = await context.Table
.Select(i => new Table {
Rank = // want to calculate the rank based on amount
}).OrderByDescending(i => i.Amount)
.ToListAsync();
I tried using the element index but for that, I need to fetch all the data to the client first.

There's no direct implementation for RANK() in EF. You are better off with using a custom LINQ query to do what you want, like,
var query = from t in context.Table
orderby t.Amount descending
select new
{
Rank = (from o in context.Table
where o.Amount > s.Amount
select o).Count() + 1
};
If you know the SQL query you want to execute, you can create a custom function or stored procedure and then execute it using Entity Framework. Please refer this.

how to get the max value of id from second table using join in entity framework in asp.net c#

I have two tables, from 1st table i want to get all records and from 2nd table i want the max id value of that record. I am using entity framework in asp.net c#.
i tried the below code but it takes only single record from first table i.e tblblogs. and leave all the records, how to get all those records by using this query? plz help me out I'll be very grateful to you. Thanks !
var query= (from c in db.tblBlogs join a in db.tblBlogMedias on c.id
equals a.BlogId where c.id==db.tblBlogMedias.Max(p=>p.id)
select new
{}

If I understood, you want to get an object with specific fields of Blogs and a list of tblBlogMedias.
You could try this code:
var query2 = (from c in db.tblBlogs
orderby c.Id descending
group c.tblBlogMedias by new { c.Id, c.Name } into gb //It will show Id and name of tblBlogs, you can use more fields if you want
select new {
Id = gb.Key.Id,
Name = gb.Key.Name, //I don't know if you have this field, but you should change it
SecondTable = gb.ToList()
})
.OrderByDescending(o => o.Id) //this orderby with FirstOrDefault() replace where c.id==db.tblBlogMedias.Max(p=>p.id)
.FirstOrDefault();

Select data from 3 tables with Linq to SQL

I have 3 tables. Orders, OrderItems and OrderItemServices. Each order can contain multiple OrderItems and each OrderItem can contain multiple OrderItemServices.
I want to get a list of data of all orders from these tables in Linq. I could write a join but how do I make an anonymous data type to in select clasue which can give me Order list in this hierarchy?
If I use navigation properties and then select OrderItemServices in side select clause shown below it would fire individual select query for each OrderItemService which I want to avoid.
from order in Orders
select new
{
ActiveOrders = order,
ActiveOrderItems =order.OrderItems,
ActiveServices = order.OrderItems.Select(o => o.OrderItemServices)
}
Is it possible to group each order with a structure of multiple items inside it and multiple services inside items?

Refer msdn to start on LINQ To SQL
To get data from three tables you can get idea from the following simple example
var data = (from product in context.Products
from department in context.Departments
from category in context.Categories
where product.DeptId == department.DeptId
&& product.CatId == category.CatId
select new
{
product.Code,
product.Name,
department.Name,
category.Name
}).Distinct.ToList();

You have to set up your context to use eager loading:
var context = new MyDataContext();
var options = new DataLoadOptions();
options.LoadWith<Orders>(x => x.OrderItems);
options.LoadWith<OrderItems>(x => x.OrderItemServices);
context.LoadOptions = options;
var query = from order in context.Orders // ... etc
Then sub items will be included in initial query result and won't cause additional requests to the database. This will use JOIN internally to retrieve all the data in one go. You can check generated SQL using SQL Server Profiler.
http://blog.stevensanderson.com/2007/12/02/linq-to-sql-lazy-and-eager-loading-hiccups/

Linq To Entities, Select multiple sets of data with one query

I've found plenty of info on how to select multiple result sets with stored procedures but nothing substantial on how to do so with a linq query.
For example, I can do sub-queries that return mulitple sets of results with something like
var query = (from school in context.Schools
where school.id == someId
select new
{
subSetA = (from student in context.Students
select student).ToList(),
subSetB = (from building in context.Buildings
select building).ToList(),
}).First();
query.subSetA; //Access subSetA
query.subSetB; //Access subSetB
Which works fine, but what if I just want to select both subSetA and subSetB without querying against the school table? I want to select two separate sets of data that gets sent to the server in one query.
Any information as to how to do this with EF 6 would be great.

Well, I'm sure there are many ways to do this, but if you want to avoid introducing a third DbSet into the mix...
var query = (from s in context.Students.Take(1)
select new
{
subSetA = context.Students.ToList(),
subSetB = context.Buildings.ToList(),
})
Then, you can use query.ToList() or maybe using query.Load() and working with context.Students.Local, etc. would work.

Linq to SQL: Sum with multiple columns select

I want to convert the following SQL code into linq to sql but can't seem to find a way
select holder_name,agent_code,sum(total)
from agent_commission
group by agent_code
Can anyone help me? Am kinda stuck with this for quite a while.
Thanks in advance
UPDATE:
I tried the following
var query = (from p in context.Agent_Commissions
group p by new
{
p.agent_code
}
into s
select new
{
amount = s.Sum(q => q.total),
}
);
How do I select the other two columns? What am I missing?

In fact your SQL query works only when the corresponding relationship between holder_name and agent_code is 1-1, otherwise the Group by agent_code won't work. So your linq query should be like this:
var query = from p in context.Agent_Commissions
group p by p.agent_code into s
select new {
holder_name = s.FirstOrDefault().holder_name,
agent_code = s.Key,
amount = s.Sum(q => q.total)
};

Here is your linq query
from a in ctx.agent_code
group a by a.holder_name, a.code into totals
select { holder_name = a.holder_name,
code = a.code,
total = totals.Sum(t=>t.total)}
Given that you have linq2sql context in ctx variable and it has your table in it.