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Execute Raw SQL Queries in Entity Framework Core

Entity Framework Core provides the DbSet.FromSql() method to execute raw SQL queries for the underlying database and get the results as entity objects.

The following example demonstrates executing a raw SQL query to MS SQL Server database.

var context = new SchoolContext();

var students = context.Students
                  .FromSql("Select * from Students where Name = 'Bill'")
                  .ToList();

In the above example, the FromSql() method is used after the Students entity set (DbSet<Student>), so the specified SQL query must return records from the Students table which will transform in Student entities. Entity Framework Core will execute the specified query to the database i.e. Select * from Students where Name = 'Bill' in the above example.

Parameterized Query

The FromSql method allows parameterized queries using string interpolation syntax in C#, as shown below. 

string name = "Bill";

var context = new SchoolContext();
var students = context.Students
                    .FromSql($"Select * from Students where Name = '{name}'")
                    .ToList();

The following is also valid.

string name = "Bill";

var context = new SchoolContext();
var students = context.Students
                    .FromSql("Select * from Students where Name = '{0}'", name)
                    .ToList();

The examples above will execute the following SQL query to the SQL Server database:

exec sp_executesql N'Select * from Students where Name = ''@p0''
',N'@p0 nvarchar(4000)',@p0=N'Bill'
go

LINQ Operators

You can also use LINQ Operators after a raw query using FromSql method.

string name = "Bill";

var context = new SchoolContext();
var students = context.Students
                    .FromSql("Select * from Students where Name = '{0}'", name)
                    .OrderBy(s => s.StudentId)
                    .ToList();

In the above example, EF Core executes the following query by combining FromSql method and OrderBy operator.

exec sp_executesql N'SELECT [s].[StudentId], [s].[Name]
FROM (
    Select * from Students where Name = ''@p0''
) AS [s]
ORDER BY [s].[StudentId]',N'@p0 nvarchar(4000)',@p0=N'Bill'
go

FromSql Limitations

  1. SQL queries must return entities of the same type as DbSet<T> type. e.g. the specified query cannot return the Course entities if FromSql is used after Students. Returning ad-hoc types from FromSql() method is in the backlog.
  2. The SQL query must return all the columns of the table. e.g. context.Students.FromSql("Select StudentId, LastName from Students).ToList() will throw an exception.
  3. The SQL query cannot include JOIN queries to get related data. Use Include method to load related entities after FromSql() method.
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