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。
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。网上还有对Dapper的扩展类，这里就不赘述了。下面只讲下简单的增删改查、数据库表间的对应关系和事务的应用。
先给出实体类的关系：
书和书评是1---n的关系。（沿用Entity Framework的实体类，virtual表示延迟加载，此处忽略）
//书 public class Book { public Book() { Reviews = new List<BookReview>(); } public int Id { get; set; } public string Name { get; set; } public virtual List<BookReview> Reviews { get; set; } public override string ToString() { return string.Format("[{0}]------《{1}》", Id, 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); } } 基本的增删改查操作由于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。
IDbConnection conn = new SqlConnection(connString);Insert
Book book = new Book(); book.Name="C#本质论"; string query = "INSERT INTO Book(Name)VALUES(@name)"; //对对象进行操作 conn.Execute(query, book); //直接赋值操作 conn.Execute(query, new {name = "C#本质论"});update
string query = "UPDATE Book SET Name=@name WHERE id =@id"; conn.Execute(query, book);delete
string query = "DELETE FROM Book WHERE id = @id"; conn.Execute(query, book); conn.Execute(query, new { id = id });query
string query = "SELECT * FROM Book"; //无参数查询，返回列表，带参数查询和之前的参数赋值法相同。 conn.Query<Book>(query).ToList(); //返回单条信息 string query = "SELECT * FROM Book WHERE id = @id"; book = conn.Query<Book>(query, new { id = id }).SingleOrDefault(); 数据库表对应关系操作 //查询图书时，同时查找对应的书评，并存在List中。实现1--n的查询操作 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.Id != book.Id) 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 = id }).Distinct().SingleOrDefault(); return b; //1--1操作 BookReview br; string query = "SELECT * FROM BookReview WHERE id = @id"; using (conn) { br = conn.Query<BookReview, Book, BookReview>(query, (bookReview, book) => { bookReview.AssoicationWithBook = book; return bookReview; }, new { id = id }).SingleOrDefault(); return br; } 事务操作 using (conn) { //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 = id }, transaction, null, null); conn.Execute(query, new { id = id }, 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); } }转载于:https://www.cnblogs.com/bosamvs/p/5945043.html
