Dapper是.NET下一個micro的ORM，它和Entity Framework或Nhibnate不同，屬于輕量級的，并且是半自動的。也就是說實體類都要自己寫。它沒有復雜的配置文件，一個單文件就可以了。給出官方地址。

http://code.google.com/p/dapper-dot-net/

個人覺得他非常好用，現在已經取代了原來的SqlHelper。優點：

使用Dapper可以自動進行對象映射！

輕量級，單文件。

支持多數據庫。

Dapper原理通過Emit反射IDataReader的序列隊列，來快速的得到和產生對象。

網上還有對Dapper的擴展類，這里就不贅述了。下面只講下簡單的增刪改查、數據庫表間的對應關系和事務的應用。

先給出實體類的關系：

?書和書評是1---n的關系。（沿用Entity Framework的實體類，virtual表示延遲加載，此處忽略）

//書 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);}}//書評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);}}

• 基本的增刪改查操作

　　由于Dapper ORM的操作實際上是對IDbConnection類的擴展，所有的方法都是該類的擴展方法。所以在使用前先實例化一個IDBConnection對象。

IDbConnection conn = new SqlConnection(connString);

Insert

Book book = new Book();book.Name="C#本質論";string query = "INSERT INTO Book(Name)VALUES(@name)"; //對對象進行操作conn.Execute(query, book); //直接賦值操作conn.Execute(query, new {name = "C#本質論"});

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"; //無參數查詢，返回列表，帶參數查詢和之前的參數賦值法相同。conn.Query<Book>(query).ToList();//返回單條信息string query = "SELECT * FROM Book WHERE id = @id";book = conn.Query<Book>(query, new { id = id }).SingleOrDefault();

• 數據庫表對應關系操作

//查詢圖書時，同時查找對應的書評，并存在List中。實現1--n的查詢操作 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) =>{//掃描第一條記錄，判斷非空和非重復if (lookup == null || lookup.Id != book.Id)lookup = book;//書對應的書評非空，加入當前書的書評List中，最后把重復的書去掉。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; }

• 事務操作

using (conn) { //開始事務 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);//提交事務transaction.Commit();}catch (Exception ex){//出現異常，事務Rollbacktransaction.Rollback();throw new Exception(ex.Message);} }

文章來源 https://www.cnblogs.com/Sinte-Beuve/p/4231053.html

轉載于:https://www.cnblogs.com/kerwincui/p/9328128.html

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