Dapper.NET 使用简单举例

概述

Dapper是.NET下一个micro的ORM，它和Entity Framework或Nhibnate不同，属于轻量级的，并且是半自动的。也就是说实体类都要自己写。它没有复杂的配置文件，一个单文件就可以了。

现在已经取代了原来的SqlHelper优点：

• 使用Dapper可以自动进行对象映射！
• 轻量级，单文件。
• 支持多数据库。
• Dapper原理通过Emit反射IDataReader的序列队列，来快速的得到和产生对象
• 由于Dapper ORM的操作实际上是对IDbConnection类的扩展，所有的方法都是该类的扩展方法。所以在使用前先实例化一个IDBConnection对象。所以调用之前，一定先加上命名空间：using Dapper;

使用举例

数据库表结构

----Book表，主表CREATE TABLE [dbo].[Book](
    [BookId] [int] IDENTITY(1,1) NOT NULL,
    [Name] [nvarchar](50) NOT NULL,
 CONSTRAINT [PK_Book] PRIMARY KEY CLUSTERED
(
    [BookId] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

GO
----BookReview类似于book评价表
CREATE TABLE [dbo].[BookReview](
    [Id] [int] IDENTITY(1,1) NOT NULL,
    [BookId] [int] NULL,
    [Content] [nvarchar](50) NULL,
 CONSTRAINT [PK_BookReview] PRIMARY KEY CLUSTERED
(
    [Id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

GO

ALTER TABLE [dbo].[BookReview]  WITH CHECK ADD  CONSTRAINT [FK_BookID_BookPreBookid] FOREIGN KEY([BookId])
REFERENCES [dbo].[Book] ([BookId])
GO

ALTER TABLE [dbo].[BookReview] CHECK CONSTRAINT [FK_BookID_BookPreBookid]
GO

实体结构

public class Book
    {
        public Book()
        {
            Reviews = new List<BookReview>();
        }
        public int BookId { get; set; }
        public string Name { get; set; }
        public virtual List<BookReview> Reviews { get; set; }
        public override string ToString()
        {
            return string.Format("[{0}]------《{1}》", BookId, Name);
        }
    }

//书评
    public class BookReview
    {
        public int Id { get; set; }
        public int BookId { get; set; }
        public virtual string Content { get; set; }
        public virtual Book AssoicationWithBook { get; set; }
        public override string ToString()
        {
            return string.Format("{0})--[{1}]\t\"{3}\"", Id, BookId, Content);
        }
    }

• Execute执行数据库脚本

        public static void OpeartData()
        {
            string sqlconnct = System.Configuration.ConfigurationManager.ConnectionStrings["myconnect"].ConnectionString;
            using (IDbConnection comm = new SqlConnection(sqlconnct))
            {
                comm.Open();
                //Book book = new Book() { Name="C#9论述",Id=1 };
                string query = "insert into Book(Name) values(@name)";
                //添加，可以执行SQL脚本

                //comm.Execute(query, book);
                //comm.Execute(query, new { name = "Java Learn" });

                query = "UPDATE Book SET  [email protected] WHERE BookId [email protected]";
                //comm.Execute(query, book);
                //comm.Execute(query, new {name="C985426",BookId=1 });

                query = "DELETE FROM Book WHERE BookId = @id";
                //var idsult=comm.Execute(query, new { name = "C985426", BookId = 1 });

                query = "select * from Book where [email protected]";
                //var ruslt = comm.Query<Book>(query).ToList();
                // var ruslt = comm.Query<Book>(query, new { BookId = 2 }).FirstOrDefault();
            }
        }

• Query执行数据库脚本查询
  • One To More 查询

  public static Book OpeartMoData()
          {
              string sqlconnct = System.Configuration.ConfigurationManager.ConnectionStrings["myconnect"].ConnectionString;
              using (IDbConnection conn = new SqlConnection(sqlconnct))
              {
                  conn.Open();
                  string query = "SELECT * FROM Book b LEFT JOIN BookReview br ON br.BookId = b.Id WHERE b.id = @id";
                  Book lookup = null;
                  //Query<TFirst, TSecond, TReturn>
                  var b = conn.Query<Book, BookReview, Book>(query,
                   (book, bookReview) =>
                   {
                       //扫描第一条记录，判断非空和非重复
                       if (lookup == null || lookup.BookId != book.BookId)
                           lookup = book;
                       //书对应的书评非空，加入当前书的书评List中，最后把重复的书去掉。
                       if (bookReview != null)
                           lookup.Reviews.Add(bookReview);
                       return lookup;
                   }, new { id = 2 }, splitOn: "id").Distinct().SingleOrDefault();
                  return b;
              }
          }

  • One To One 查询

   public static BookReview OpeartData1T1()
          {
              string sqlconnct = System.Configuration.ConfigurationManager.ConnectionStrings["myconnect"].ConnectionString;
              using (IDbConnection conn = new SqlConnection(sqlconnct))
              {
                  BookReview br;
                  string query = "SELECT br.Id,b.BookId,Content,Name FROM BookReview br  inner JOIN Book b ON br.BookId = b.BookId  WHERE br.id = @id";
                  using (conn)
                  {
                      br = conn.Query<BookReview, Book, BookReview>(query,
                     (bookReview, book) =>
                     {
                         bookReview.AssoicationWithBook = book;
                         return bookReview;
                     }, new { id = 4 }, splitOn: "BookId",commandType:CommandType.StoredProcedure).FirstOrDefault();
                      return br;
                  }
              }
          }

  • 执行事务

   public static void BookTransaction()
          {
              string sqlconnct = System.Configuration.ConfigurationManager.ConnectionStrings["myconnect"].ConnectionString;
              using (IDbConnection conn = new SqlConnection(sqlconnct))
              {
                  conn.Open();
                  //开始事务
                  IDbTransaction transaction = conn.BeginTransaction();
                  try
                  {
                      string query = "DELETE FROM Book WHERE id = @id";
                      string query2 = "DELETE FROM BookReview WHERE BookId = @BookId";
                      conn.Execute(query2, new { BookId = 2 }, transaction, null, null);
                      conn.Execute(query, new { id = 2 }, transaction, null, null);
                      //提交事务
                      transaction.Commit();
                  }
                  catch (Exception ex)
                  {
                      //出现异常，事务Rollback
                      transaction.Rollback();
                      throw new Exception(ex.Message);
                  }
              }
          }