<address id="xvfrz"></address>

              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‘
              
              相关文章
              相关标签/搜索
              2019年所有开马的记录