PetaPoco的使用Demo手册

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PetaPoco的使用Demo手册
//初始化数据库连接var db=new PetaPoco.Database("connectionStringName");//查询单个值long count=db.ExecuteScalar<long>("SELECT Count(*) FROM articles");//返回一条记录var a = db.SingleOrDefault<article>("SELECT * FROM articles WHERE article_id=@0", 123));//返回一条记录，可以省略select，用where开头,会自动查询出全部字段（不是*号）var a=db.SingleOrDefault<article>("WHERE article_id=@0", 123);//返回一条记录，可以From开头,会自动查询出全部字段（不是*号）var a = db.SingleOrDefault<article>("FROM whatever WHERE id=@0", 123);//如果有主键，可以这样写var a = db.SingleOrDefault<article>(some_id);//分页，分页的代码会自动生成var result=db.Page<article>(1, 20,"SELECT * FROM articles WHERE category=@0 ORDER BY date_posted DESC", "coolstuff");// 逐行查询每条记录，一次只从数据库表中取一条数据foreach (var a in db.Query<article>("SELECT * FROM articles")){    Console.WriteLine("{0} - {1}", a.article_id, a.title);}//动态查询，返回dynamic，这种方式不支持自动添加Selectforeach (var a in db.Fetch<dynamic>("SELECT * FROM articles")){    Console.WriteLine("{0} - {1}", a.article_id, a.title);}//查询单个字段，返回非Poco对象,支持所有的Type.IsValueType,字符串和byte数组foreach (var x in db.Query<long>("SELECT article_id FROM articles")){    Console.WriteLine("Article ID: {0}", x);}//检查主键是否存在if (db.Exists<article>(23))     db.Delete <article>（23）;//执行Sql，不返回值db.Execute("DELETE FROM articles WHERE draft<>0");//插入记录// Create the articlevar a=new article();a.title="My new article";a.content="PetaPoco was here";a.date_created=DateTime.UtcNow;// Insert itdb.Insert(a);//修改记录// Get a recordvar a=db.SingleOrDefault<article>("SELECT * FROM articles WHERE article_id=@0", 123);// Change ita.content="PetaPoco was here again";// Save itdb.Update(a);//修改一个属性更简洁的写法db.Update("articles", "article_id", new { title="New title" }, 123);//更新的另一种写法db.Update<article>("SET title=@0 WHERE article_id=@1", "New Title", 123);//更新指定的字段a.Update(new string[] { "title" });//也可以这样更新db.Update<user>(u, new string[] { "title" });//删除记录//通过主键删除db.Delete(a);//自定义删除db.Delete<article>("WHERE article_id=@0", 123);//事务,而且事物可以嵌套哦using(var scope = db.GetTransaction()){    //todo: Do transacted updates here    // Commit    scope.Complete();}//支持存储过程,还不支持out 参数？db.Query<type>("CALL storedproc")     // MySQL stored procdb.Query<type>("EXECUTE stmt")        // MySQL prepared statementdb.Query<type>("EXECUTE storedproc")  // SQL Server//执行SqldatabaseQuery.Execute("insert into temp1 (t) values (@0)",                 new SqlParameter() { SqlDbType = SqlDbType.VarBinary, Value = DbNull.Value });//组装Sqlvar id=123;var a=db.Query<article>(PetaPoco.Sql.Builder    .Append("SELECT * FROM articles")    .Append("WHERE article_id=@0", id)    .Append("AND date_created<@0", DateTime.UtcNow))//动态组装Sqlvar id=123;var sql=PetaPoco.Sql.Builder    .Append("SELECT * FROM articles")    .Append("WHERE article_id=@0", id);if (start_date.HasValue)    sql.Append("AND date_created>=@0", start_date.Value);if (end_date.HasValue)    sql.Append("AND date_created<=@0", end_date.Value);var a=db.Query<article>(sql)//通过命名的参数来组装Sqlsql.Append("AND date_created>=@start AND date_created<=@end",                 new                 {                     start=DateTime.UtcNow.AddDays(-2),                     end=DateTime.UtcNow                 }            );//组装Sql还可以这样var sql=PetaPoco.Sql.Builder()            .Select("*")            .From("articles")            .Where("date_created < @0", DateTime.UtcNow)            .OrderBy("date_created DESC");//还可以更复杂var sql = Sql.Builder    .Select("*")    .From("articles")    .LeftJoin("comments").On("articles.article_id=comments.article_id");
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