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You can execute native raw SQL query against the database using DBContext. You can execute the following types of queries:
As we have seen in one of the previous chapters, DBSet has SQLQuery() method to write raw SQL queries which return entity instances. The returned objects will be tracked by the context, just as they would be if they were returned by a LINQ query. For example:
using (var ctx = new SchoolDBEntities()) { var studentList = ctx.Students.SqlQuery("Select * from Student").ToList<Student>(); }
However, columns returned by SQL query should match the property of an entity type of DBSet otherwise, it will throw an exception. For example:
using (var ctx = new SchoolDBEntities()) { var studentName = ctx.Students.SqlQuery("Select studentid, studentname from Student where studentname=‘New Student1‘").ToList(); }
If you change the column name in query, then it will throw an exception because it must match column names:
using (var ctx = new SchoolDBEntities()) { //this will throw an exception var studentName = ctx.Students.SqlQuery("Select studentid as id, studentname as name from Student where studentname=‘New Student1‘").ToList(); }
A SQL query returning instances of any type, including primitive types, can be created using the SqlQuery method on the Database class. For example:
using (var ctx = new SchoolDBEntities()) { //Get student name of string type string studentName = ctx.Database.SqlQuery<string>("Select studentname from Student where studentid=1").FirstOrDefault<string>(); }
ExecuteSqlCommnad method is useful in sending non-query commands to the database, such as the Insert, Update or Delete command. For example:
using (var ctx = new SchoolDBEntities()) { //Update command int noOfRowUpdated = ctx.Database.ExecuteSqlCommand("Update student set studentname =‘changed student by command‘ where studentid=1"); //Insert command int noOfRowInserted = ctx.Database.ExecuteSqlCommand("insert into student(studentname) values(‘New Student‘)"); //Delete command int noOfRowDeleted = ctx.Database.ExecuteSqlCommand("delete from student where studentid=1"); }
Entity Framework Tutorial Basics（39）：Raw SQL Query
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原文地址：http://www.cnblogs.com/purplefox2008/p/5649455.html
