CODEWITHSUNDEEP
linqpad
Ravi Ram
Ravi Ram

Reputation: 24488

LinqPad - Convert SQL to Linq command

I recently purchased LINQPad in hopes that it would allow me to convert SQL statements into LINQ statements.

Using LINQPad, I am able to attach a DB and run the SQL statement which returns the results I need.

But I can not find a 'command' to convert that SQL statement into LINQ.

Can you please let me know how to convert SQL to LINQ by using LINQPad OR another tool?

Upvotes: 22

Views: 106663

Answers (3)

Joe Albahari
Joe Albahari

Reputation: 31004

There is a tool called Linqer, but be careful: transliterating from SQL to LINQ can give you the worst of both worlds.

For instance, suppose you want all purchases of $1000 or greater paid for in cash or by customers who live in Washington. Here's the query in SQL:

SELECT p.*
FROM Purchase p
    LEFT OUTER JOIN 
        Customer c INNER JOIN Address a ON c.AddressID = a.ID
    ON p.CustomerID = c.ID  
WHERE
   (a.State = 'WA' || p.CustomerID IS NULL)
    AND p.ID in
    (
        SELECT PurchaseID FROM PurchaseItem
        GROUP BY PurchaseID HAVING SUM (SaleAmount) > 1000
    )

How would translate this to LINQ? The wrong way is to transliterate the query into LINQ, trying to reproduce the outer and inner joins, subquery and group clause. The right way is to map your original query (in English) directly into LINQ, leveraging LINQ's linear flow of data and association properties:

I want all purchases...

from p in db.Purchases

...of $1000 or greater...

where p.PurchaseItems.Sum (pi => pi.SaleAmount) > 1000

...paid for in cash...

where p.Customer == null

...or by customers who live in Washington

|| p.Customer.Address.State == "WA"

Here's the final query:

from p in db.Purchases
where p.PurchaseItems.Sum (pi => pi.SaleAmount) > 1000
where p.Customer == null || p.Customer.Address.State == "WA"
select p

More info here.

Upvotes: 51

Akim
Akim

Reputation: 8689

In general there are no tools to covert SQL to Linq as @andres-abel mention before, but sometimes you have to write Linq that will execute exactly as specified SQL (for example because of performance issues, backward compatability or some other reasons).

In this case I'll advice you to do reverse engineering by yourself:

  1. configure logging of dump SQL statements generated by Linq to stdout using
  2. manually rewrite Linq statement until you'll get what you need

Upvotes: 10

Anders Abel
Anders Abel

Reputation: 69290

LinqPad contains no SQL->LINQ translator. LinqPad does actually not contain any LINQ->SQL translator either. It relies on the .Net Linq-to-Sql library or Entity framework for the translation.

I don't know of any other tool with that capability either. In simple cases it would be possible to make one, but for more complex scenarios it would be impossible as there is no LINQ expression that matches some SQL constructs.

Upvotes: 8

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