Linq to SQL Like Operator

Starting from a simple query from Northwind Database;

var query = from c in ctx.Customers
            where c.City == "London"
            select c;

The query that will be sent to the database will be:

SELECT CustomerID, CompanyName, ...
FROM dbo.Customers
WHERE City = [London]

There are some ways to write a Linq query that results in using Like Operator in the SQL statement:

1.- Using String.StartsWith or String.Endswith
Writing the following query:

var query = from c in ctx.Customers
            where c.City.StartsWith("Lo")
            select c;

will generate this SQL statement:

SELECT CustomerID, CompanyName, ...
FROM    dbo.Customers
WHERE  City LIKE [Lo%]

which is exactly what we wanted. Same goes with String.EndsWith.

But, what is we want to query the customer with city name like “L_n%”? (starts with a Capital ‘L’, than some character, than ‘n’ and than the rest of the name). Using the query

var query = from c in ctx.Customers
            where c.City.StartsWith("L") && c.City.Contains("n")
            select c;

generates the statement:

SELECT CustomerID, CompanyName, ...
  FROM dbo.Customers
 WHERE City LIKE [L%]
   AND City LIKE [%n%]

which is not exactly what we wanted, and a little more complicated as well.

2.- Using SqlMethods.Like method
Digging into System.Data.Linq.SqlClient namespace, I found a little helper class called SqlMethods, which can be very usefull in such scenarios. SqlMethods has a method called Like, that can be used in a Linq to SQL query:

var query = from c in ctx.Customers
            where SqlMethods.Like(c.City, "L_n%")
            select c;

This method gets the string expression to check (the customer’s city in this example) and the patterns to test against which is provided in the same way you’d write a LIKE clause in SQL.

Using the above query generated the required SQL statement:

SELECT CustomerID, CompanyName, ...
FROM    dbo.Customers
WHERE  City LIKE [L_n%]

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