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  • EFCore执行Sql语句的方法:FromSql与ExecuteSqlCommand

    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

    public class MSSqlDBContext : DbContext
        {
            protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
            {
                optionsBuilder.UseSqlServer(@"data source=localhost;initial catalog=TestDB;Integrated Security=True;");
            }
            public DbSet<Person> Person { get; set; }
            public DbSet<Address> Address { get; set; }
    }
    
        [Table(nameof(Person))]
        public class Person
        {
            public int id { get; set; }
            public string name { get; set; }
            [Column(TypeName = "datetime")]
            public DateTime? birthday { get; set; }
            public int? addrid { get; set; }
    }
    
        [Table(nameof(Address))]
        public class Address
        {
            public int id { get; set; }
            public string fullAddress { get; set; }
            public double? lat { get; set; }
            public double? lon { get; set; }
        }
    

      

    ExecuteSqlCommand

    EFCore的ExecuteSqlCommand和EF6的一样,执行非查询的Sql语句:

    var db = new MSSqlDBContext();
    2             db.Database.ExecuteSqlCommand($"update {nameof(Person)} set [email protected] where [email protected]", new[] 
    3             {
    4                 new SqlParameter("name", "tom1"),
    5                 new SqlParameter("id", 1),
    6             });
    

      

    FromSql

    官方参考文档:https://docs.microsoft.com/en-us/ef/core/querying/raw-sql

    简单使用

     var db = new MSSqlDBContext();
    2             var name = "tom";
    3             var list = db.Set<Person>().FromSql($"select * from {nameof(Person)} where {nameof(name)}[email protected]{nameof(name)} ", 
    4                 new SqlParameter(nameof(name), name)).ToList();
    

      生成的Sql:

    exec sp_executesql N‘select * from Person where [email protected] 
    ‘,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<Person>().FromSql($"select name from {nameof(Person)} ").ToList();
    

      那么改为:

    db.Set<Person>().Select(l => l.name).FromSql($"select name from {nameof(Person)} ").ToList();
    

      

    执行存储过程

     var db = new MSSqlDBContext();
    db.Set<Person>().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

    var db = new MSSqlDBContext();
    db.Set<Person>().FromSql($"select * from {nameof(Person)} where [email protected] ", new SqlParameter("@name", "tom"))
                    .Select(l => new { l.name, l.birthday }).ToList();
    

      生成的Sql:

    exec sp_executesql N‘SELECT [l].[name], [l].[birthday]
    FROM (
        select * from Person where [email protected] 
    ) AS [l]‘,N‘@name nvarchar(3)‘,@name=N‘tom‘
    

      

    inner join + order by

    var db = new MSSqlDBContext();
                  (from p in db.Set<Person>().FromSql($"select * from {nameof(Person)} ")
                  join a in db.Set<Address>().Where(l => true)
                  on p.addrid equals a.id
                  select new { p.id, p.name, a.fullAddress }).OrderBy(l => l.id).ToList();
    

      生成的Sql:

    SELECT [p].[id], [p].[name], [t].[fullAddress]
    FROM (
        select * from Person 
    ) AS [p]
    INNER JOIN (
        SELECT [l0].*
        FROM [Address] AS [l0]
    ) AS [t] ON [p].[addrid] = [t].[id]
    ORDER BY [p].[id]
    

      

    left join + order by

    var db = new MSSqlDBContext();
                  (from p in db.Set<Person>().FromSql($"select * from {nameof(Person)} ")
                  join a in db.Set<Address>().Where(l => true)
                 on p.addrid equals a.id into alist
                  from a in alist.DefaultIfEmpty()
                  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:

                 (from p in db.Set<Person>().Where(l => true)
                  join a in db.Set<Address>().Where(l => true)
                  on p.addrid equals a.id into alist
                  from a in alist.DefaultIfEmpty()
                  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

    public static IList<T> SqlQuery<T>(DbContext db, string sql, params object[] parameters)
                where T : new()
            {
                //注意:不要对GetDbConnection获取到的conn进行using或者调用Dispose,否则DbContext后续不能再进行使用了,会抛异常
                var conn = db.Database.GetDbConnection();
                try
                {
                    conn.Open();
                    using (var command = conn.CreateCommand())
                    {
                        command.CommandText = sql;
                        command.Parameters.AddRange(parameters);
                        var propts = typeof(T).GetProperties();
                        var rtnList = new List<T>();
                        T model;
                        object val;
                        using (var reader = command.ExecuteReader())
                        {
                            while (reader.Read())
                            {
                                model = new T();
                                foreach (var l in propts)
                                {
                                    val = reader[l.Name];
                                    if (val == DBNull.Value)
                                    {
                                        l.SetValue(model, null);
                                    }
                                    else
                                    {
                                        l.SetValue(model, val);
                                    }
                                }
                                rtnList.Add(model);
                            }
                        }
                        return rtnList;
                    }
                }
                finally
                {
                    conn.Close();
                }
            }
    

      使用:

    var db = new MSSqlDBContext();
                string name = "tom";
                var list = SqlQuery<PAModel>(db,
                    $" select p.id, p.name, a.fullAddress, a.lat, a.lon " +
                    $" from ( select * from {nameof(Person)} where {nameof(name)}[email protected]{nameof(name)} ) as p " +
                    $" left join {nameof(Address)} as a on p.addrid = a.id ",
                    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 [email protected] ) as p  left join Address as a on p.addrid = a.id ‘,N‘@name nvarchar(3)‘,@name=N‘tom‘
    
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