Entity Framework——执行sql语句

EF版本：6.0.0

EF对大量数据或多表连接一次操作耗时较大，或要求响应时间尽可能小，因此采用EF框架执行SQL语句的方案

1DbContext.Database

这个类包含了大量的操作方法，见截图：

查询方法举例：

using (CustomDbContext db = new CustomDbContext())
            {
                string sql = "SELECT * FROM collections LEFT JOIN collectionusers ON collections.`Id`=collectionusers.`Collection_Id`";
                var task = db.Database.SqlQuery<Collection>(sql).ToListAsync();
                task.Wait();
                var r = task.Result;
            }

删除方法举例：

using (CustomDbContext db = new CustomDbContext())
            {
                string sql = "delete from collectionusers where Id=@id";
                var num = db.Database.ExecuteSqlCommand(sql, new MySqlParameter("@id", ));
            }

注意操作Mysql数据库，一定要是有MySqlParameter而不能使用SqlParameter，使用SqlParameter会抛出异常：Only MySqlParameter objects may be stored

更新方法举例：

using (CustomDbContext db = new CustomDbContext())
            {
                string sql = "update collectionusers set InsertTime=@time where Id=@id";
                var num = db.Database.ExecuteSqlCommand(sql, new MySqlParameter("@time", DateTime.Now),new MySqlParameter("@id", ));
            }

插入方法举例：

using (CustomDbContext db = new CustomDbContext())
            {
                db.Database.ExecuteSqlCommand("SET SQL_SAFE_UPDATES=0");//不启用更新安全模式
                db.Database.ExecuteSqlCommand("SET FOREIGN_KEY_CHECKS=0");//取消外键约束
                string sql = "INSERT INTO collectionusers (`InsertTime`, `Collection_Id`, `User_Id`)VALUES(@insertTime,@cid, @uid)";
                var num = db.Database.ExecuteSqlCommand(sql, new MySqlParameter("@insertTime", DateTime.Now), new MySqlParameter("@cid", ), new MySqlParameter("@uid",));
            }

事务操作举例：

CustomDbContext db = null;
            DbContextTransaction tran = null;
            try
            {
                db = new CustomDbContext();
                tran = db.Database.BeginTransaction();
                db.Database.ExecuteSqlCommand("SET SQL_SAFE_UPDATES=0");//不启用更新安全模式
                db.Database.ExecuteSqlCommand("SET FOREIGN_KEY_CHECKS=0");//取消外键约束
                string sql = "INSERT INTO collectionusers (`InsertTime`, `Collection_Id`, `User_Id`)VALUES(@insertTime,@cid, @uid)";
                var num = db.Database.ExecuteSqlCommand(sql, new MySqlParameter("@insertTime", DateTime.Now), new MySqlParameter("@cid", ), new MySqlParameter("@uid", ));
                tran.Commit();
            }
            catch
            {
                tran.Rollback();
            }
            finally
            {
                if (db != null) db.Dispose();
                if (tran != null) tran.Dispose();
            }

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时间仓促，水平有限，如有不当之处，欢迎指正。