前言
在EFCore中执行Sql语句的方法为：FromSql与ExecuteSqlCommand；在EF6中的为SqlQuery与ExecuteSqlCommand，而FromSql和SqlQuery有很大区别，FromSql返回值为IQueryable，因此为延迟加载的，可以与Linq扩展方法配合使用，但是有不少的坑(EFCore版本为1.1.0)，直接执行Sql语句的建议不要使用FromSql，但是EFCore中并没有提供SqlQuery方法，因此下面会贴出SqlQuery的实现代码供大家参考，以便在EFCore中能使用。
FromSql和ExecuteSqlCommand的使用
测试时使用了SqlServer2008和SqlServer Profiler进行Sql语句捕捉，EFCore的版本为1.1.0。
测试的Entity Model与DbContext
View Code ExecuteSqlCommand
EFCore的ExecuteSqlCommand和EF6的一样，执行非查询的Sql语句：
1 var db = new MSSqlDBContext();2 db.Database.ExecuteSqlCommand($"update {nameof(Person)} set name=@name where id=@id", new[] 3 {4 new SqlParameter("name", "tom1"),5 new SqlParameter("id", 1),6 }); FromSql
官方参考文档：
简单使用
1 var db = new MSSqlDBContext();2 var name = "tom";3 var list = db.Set().FromSql($"select * from {nameof(Person)} where {nameof(name)}=@{nameof(name)} ", 4 new SqlParameter(nameof(name), name)).ToList();
生成的Sql：
exec sp_executesql N'select * from Person where name=@name ',N'@name nvarchar(3)',@name=N'tom'
注意：
默认生成的为Person的Model，如果Select获取的字段中不包含Person中的某字段就会抛异常了，例如：下面的语句只获取name字段，并没有包含Person的其他字段，那么抛异常：The required column 'id' was not present in the results of a 'FromSql' operation.
db.Set().FromSql($"select name from {nameof(Person)} ").ToList();
那么改为：
db.Set().Select(l => l.name).FromSql($"select name from {nameof(Person)} ").ToList();
执行存储过程
1 var db = new MSSqlDBContext();2 db.Set().FromSql("exec testproc @id", new SqlParameter("id", 1)).ToList();
生成的Sql：
exec sp_executesql N'exec testproc @id',N'@id int',@id=1
与Linq扩展方法配合使用
1 var db = new MSSqlDBContext();2 db.Set().FromSql($"select * from {nameof(Person)} where name=@name ", new SqlParameter("@name", "tom"))3 .Select(l => new { l.name, l.birthday }).ToList();
生成的Sql：
View Code inner join + order by
1 var db = new MSSqlDBContext();2 (from p in db.Set().FromSql($"select * from {nameof(Person)} ")3 join a in db.Set ().Where(l => true)4 on p.addrid equals a.id5 select new { p.id, p.name, a.fullAddress }).OrderBy(l => l.id).ToList();
生成的Sql：
View Code left join + order by
1 var db = new MSSqlDBContext();2 (from p in db.Set().FromSql($"select * from {nameof(Person)} ")3 join a in db.Set ().Where(l => true)4 on p.addrid equals a.id into alist5 from a in alist.DefaultIfEmpty()6 select new { p.id, p.name, fullAddress = a == null ? null : a.fullAddress }).OrderBy(l => l.id).ToList();
生成的Sql：(生成的Sql很有问题，order by后面多了[p].[addrid]，而且生成的select的字段也是多了)
SELECT [p].[id], [p].[addrid], [p].[birthday], [p].[name], [t].[id], [t].[fullAddress], [t].[lat], [t].[lon]FROM ( select * from Person ) AS [p]LEFT JOIN ( SELECT [l0].[id], [l0].[fullAddress], [l0].[lat], [l0].[lon] FROM [Address] AS [l0]) AS [t] ON [p].[addrid] = [t].[id]ORDER BY [p].[id], [p].[addrid]
将FromSql换成Where扩展方法试试：
1 (from p in db.Set().Where(l => true)2 join a in db.Set ().Where(l => true)3 on p.addrid equals a.id into alist4 from a in alist.DefaultIfEmpty()5 select new { p.id, p.name, fullAddress = a == null ? null : a.fullAddress }).OrderBy(l => l.id).ToList();
EFCore生成的Sql（order by后面还是多了[addrid]，select的字段也是多了）：
SELECT [l].[id], [l].[addrid], [l].[birthday], [l].[name], [t].[id], [t].[fullAddress], [t].[lat], [t].[lon]FROM [Person] AS [l]LEFT JOIN ( SELECT [l1].[id], [l1].[fullAddress], [l1].[lat], [l1].[lon] FROM [Address] AS [l1]) AS [t] ON [l].[addrid] = [t].[id]ORDER BY [l].[id], [l].[addrid]
而在EF6中生成的Sql，比EFCore的生成好多了：
SELECT [Project1].[id] AS [id], [Project1].[name] AS [name], [Project1].[C1] AS [C1] FROM ( SELECT [Extent1].[id] AS [id], [Extent1].[name] AS [name], CASE WHEN ([Extent2].[id] IS NULL) THEN CAST(NULL AS varchar(1)) ELSE [Extent2].[fullAddress] END AS [C1] FROM [dbo].[Person] AS [Extent1] LEFT OUTER JOIN [dbo].[Address] AS [Extent2] ON [Extent1].[addrid] = [Extent2].[id] ) AS [Project1] ORDER BY [Project1].[id] ASC
结果说明
FromSql不能代替原来EF6的SqlQuery使用，而且结合Linq扩展方法使用的时候生成的Sql会存在一些问题(EFCore版本为：1.1.0)，那么为了能在EFCore中执行Sql查询语句，下面提供对SqlQuery方法的实现。
SqlQuery的实现
View Code 使用：
1 var db = new MSSqlDBContext();2 string name = "tom";3 var list = SqlQuery(db,4 $" select p.id, p.name, a.fullAddress, a.lat, a.lon " +5 $" from ( select * from {nameof(Person)} where {nameof(name)}=@{nameof(name)} ) as p " +6 $" left join {nameof(Address)} as a on p.addrid = a.id ",7 new[] { new SqlParameter(nameof(name), name) });
生成的Sql：
exec sp_executesql N' select p.id, p.name, a.fullAddress, a.lat, a.lon from ( select * from Person where name=@name ) as p left join Address as a on p.addrid = a.id ',N'@name nvarchar(3)',@name=N'tom'