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.Net輕量級ORM-NPoco的使用方法

阿新 • • 發佈：2019-01-19

文章引用自NPoco官方Wiki，地址：https://github.com/schotime/NPoco/wiki，因公司網路不穩定，有時無法訪問，特將其摘抄。

Home

Adam Schroder edited this page on 1 Jul 2016 · 49 revisions

Welcome to the NPoco wiki! NPoco is a fork of PetaPoco with a handful of extra features.

Getting Started: Your first query

  1. publicclassUser
  2. {
  3. public
     
    intUserId{get;set;}
  4. publicstringEmail{get;set;}
  5. }
  6. using(IDatabase db =newDatabase("connStringName"))
  7. {
  8. List<User> users = db.Fetch<User>("select userId, email from users");
  9. }

Note: Database needs to be disposed to close the connection (think of it as your connection object).

This works by mapping the column names to the property names on the User

 object. This is a case-insensitive match.
There is no mapping setup needed for this (query only) scenario.

Available on NuGet: 
Also checkout the JabbR room if you have a question. Here are the release notes.

Mapping

Adam Schroder edited this page on 21 Apr 2016 · 10 revisions

By default no mapping is required. It will be assumed that the table name will be the class name and the primary key will be 'Id' if its not specified with the attributes below.

Basic mapping is done via attributes. The most used ones are:

  1. [TableName] This takes a "name" parameter which indicates the table for which the Poco class will be mapped to.

  2. [PrimaryKey] This has a "columnName" parameter which takes the column name of the primary key for the table. Multiple primary keys can be specified by separating the columns with a comma. There is also an "autoIncrement" property which is used to indicate whether the primary key column is auto incremented e.g. identity column in Sql Server. By default this is true. For Oracle there is also a "sequenceName" property which will be used when inserting data with Oracle.

  3. [Column] This is used if the column name does not match the property name.

  4. [Ignore] This property will be ignored and cannot be mapped to.

  5. [ResultColumn] Properties marked with the Result column can be mapped into, however these properties will not be included in inserts or updates. Note: These columns will need to be explicitly specified in the SQL. It will not be included in the auto generated SQL.

  6. [ComputedColumn] Properties with the Computed column attribute work the same way as the Result column attributes however they will be auto selected in the SQL.

  7. [SerializedColumn] (v3+ only) Properties with the Serialized column attribute will serialize their data with the default serializer unless changed by implementing a IColumnSerializer. There is a NPoco.JsonNet library which allows you to use the JsonNetColumnSerializer. These are configured once by:

  1. DatabaseFactory.ColumnSerializer=newJsonNetColumnSerializer();

Example

  1. [TableName("Users")]
  2. [PrimaryKey("UserId")]
  3. publicclassUser
  4. {
  5. publicintUserId{get;set;}
  6. [Column("emailAddress")]
  7. publicstringEmail{get;set;}
  8. [ResultColumn]
  9. publicstringExtraInfo{get;set;}
  10. [Ignore]
  11. publicintTemp{get;set;}
  12. }

If you don't like attribute based mapping, the take a look at fluent / convention based mapping

Query Single Object

schotime edited this page on 27 Apr 2012 · 3 revisions

Selecting an object from the database can be done in a few different ways.

By Id

The easiest way to load an object from the database is by passing the primary key to the SingleById<T>() method.

  1. IDatabase db =newDatabase("connStringName");
  2. User u = db.SingleById<User>(3);

Via SQL

Below you can see that only the where is specified. If you don't explicitly supply the select clause it will be automatically generated for you and the where will then be appended.

  1. User u = db.Single<User>("where emailaddress = @0","[email protected]");
  2. or
  3. User u = db.Single<User>("select u.* from users u where emailaddress = @0","[email protected]");

Both these methods have a 'OrDefault' method if you are unsure that the object will exist. If it doesn't exist and you don't use the 'OrDefault' override it will throw an exception.

There are also First<T> and FirstOfDefault<T> which will not throw an exception if more than 1 record is returned.

Create Read Update Delete

Ryan Gates edited this page on 28 Jun 2016 · 5 revisions

This wiki page refers to the User class found here.

Inserting a new record

  1. IDatabase db =newDatabase("connStringName");
  2. User u =newUser()
  3. {
  4. Email="[email protected]",
  5. LastLoggedIn=DateTime.UtcNow
  6. };
  7. db.Insert(u);

This will insert the User object into the users table generating a new identity value. This value will be populated back into the object after the insert statement. For example, the following would be true.

Reading the new record

  1. var user = db.SingleById(u.UserId);
  2. Assert.AreEqual(u.Email, user.Email);

Updating the record

Once I have the object, I can update its properties. After calling the Update method, those changes will be persisted to the database.

  1. var user = db.SingleById(1);
  2. user.Email="[email protected]";
  3. db.Update(user);

Deleting the record

If I decide I no longer need the record I can delete it in a very similar fashion to Insert and Update. That is by passing the object to the Delete method. Just the primary key value can also be passed to the Delete method, however the generic type parameter will need to be specified.

  1. var user = db.SingleById(1);
  2. db.Delete(user);

or

  1. db.Delete<User>(1);

Upsert the record

This will insert a record if it is new or update an existing record if it already exists. Its existence is determined by its primary key.

  1. IDatabase db =newDatabase("connStringName");
  2. User u =newUser()
  3. {
  4. Email="[email protected]",
  5. LastLoggedIn=DateTime.UtcNow
  6. };
  7. db.Save(u);

Query List

schotime edited this page on 27 Apr 2012 · 1 revision

Here are some of the ways to fetch multiple rows from the database.

Eager

1: Fetch all

  1. List<User> users = db.Fetch<User>();

2: Fetch with criteria

  1. List<User> users = db.Fetch<User>("where isActive = 1");

3: Fetch with raw SQL

  1. List<User> users = db.Fetch<User>("select u.* from users where u.isActive = 1");

Lazy

Warning: The following method Query<T> uses the yield keyword. It will only run the query when the results are being iterated over. Please use the Fetch<T> method if you don't fully understand this concept.

  1. List<User> users = db.Query<User>("select u.* from users where u.isActive = 1");

Query Paging

schotime edited this page on 23 Mar 2013 · 3 revisions

There are two main methods used for paging.

Page<T>

  1. IDatabase db =newDatabase("connStringName");
  2. Page<T> pagedUsers = db.Page<User>(2,10,"select u.* from users u order by userid");

where Page<T> is defined by:

  1. publicclassPage<T>
  2. {
  3. publiclongCurrentPage{get;set;}
  4. publiclongTotalPages{get;set;}
  5. publiclongTotalItems{get;set;}
  6. publiclongItemsPerPage{get;set;}
  7. publicList<T>Items{get;set;}
  8. }

Note: You must provide an order by statement in your SQL statement so that the query knows in which order you want your data to be paged.

The first parameter to the Page<T> method is the page number. This number begins at 1 for the first page. The second parameter is the size of the page. In the example above, the second page with 10 users in it will be returned.

SkipTake<T>

The SkipTake<T> method is very similar to the Skip and Take methods in LINQ. It has the same number of parameters as the Page<T> method, but instead of the first parameter being the page number, it is the number of records to skip. The second parameter is the number of records to return after x number of records have been skipped. To return the same results as the Page<T>method, the query would be as follows:

            
  

           

              
              

            

            
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.Net輕量級ORM-NPoco的使用方法

     
 
                

文章引用自NPoco官方Wiki，地址：https://github.com/schotime/NPoco/wiki，因公司網路不穩定，有時無法訪問，特將其摘抄。

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Adam Schroder edited this page on 1 Jul 201 



  
 

    


    
    
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