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[ASP.net教程]Win10 UWP 开发系列:支持异步的SQLite


上篇文章已经实现了在UWP中使用SQLite作为本地存储,作为移动端的程序,及时响应用户的操作是提高用户体验的重要途径,因此UWP的很多api都是异步的。那么如何使SQLite支持异步呢?

参考SQLite.Net-PCL的github页面:https://github.com/oysteinkrog/SQLite.Net-PCL

可以看到SQLite.Net-PCL是支持异步的,在创建数据库链接的时候,可以创建同步的SQLiteConnection,也可以创建异步的SQliteAsyncConnection:

SQliteAsyncConnection

The SQLiteAsyncConnection class now takes a Func in the constructor instead of a path. This is done because the async classes are now just meant to be wrappers around the normal sqlite connection.

To use SQLiteAsyncConnection just create an instance of a SQLiteConnectionWithLock and pass in that through a func, e.g.: new SQLiteAsyncConnection(()=>_sqliteConnectionWithLock);

Please be aware that the Task.Run pattern used in SQLiteAsyncConnection can be considered an anti-pattern (libraries should not provide async methods unless they are truly async). This class is maintained for backwards compatability and for use-cases where async-isolation is handy.


 

在之前的版本中,创建SQLiteAsyncConnection和SQLiteConnection的写法是类似的,都是传入一个数据库文件地址即可,但新版本中异步的构造函数有点变化,需要传入一个Func。

接下来我们看一下如何使用异步的方式来使用SQLite。

一、添加SQLite.Net.Async-PCL支持

还是在上个例子里直接改吧,首先我们之前添加的SQLite.Net-PCL是不支持异步的,需要添加另一个nuget包:

装了这个就可以使用异步的了。

二、创建异步的数据库链接

 
public SQLiteAsyncConnection GetDbConnectionAsync(){var connectionFactory = new Func<SQLiteConnectionWithLock>(() => new SQLiteConnectionWithLock(new SQLitePlatformWinRT(), new SQLiteConnectionString(DbFilePath, storeDateTimeAsTicks: false)));var asyncConnection = new SQLiteAsyncConnection(connectionFactory);return asyncConnection;

 

 

把初始化方法改为:

public async Task InitAsync(){DbFilePath = Path.Combine(Windows.Storage.ApplicationData.Current.LocalFolder.Path, DbFileName);var db = GetDbConnectionAsync();await db.CreateTableAsync<UserItem>();}

 


 

注意要在StartupFunctions.cs文件里调用这个异步的,把原来那个Init方法注释掉。

三、异步访问数据库

其实之后就没有太多可说的了,就是把原来的同步方法改成异步的就可以了,比如插入数据:

public async Task<int> InsertUserAsync(UserItem item){int result = 0;var conn = DbContext.Instance.GetDbConnectionAsync();result = await conn.InsertAsync(item);return result;}

 


 

获取全部数据:

public async Task<List<UserItem>> GetAllUserAsync(){List<UserItem> result = new List<UserItem>();var conn = DbContext.Instance.GetDbConnectionAsync();result = await conn.Table<UserItem>().ToListAsync();return result;}

 


 

查询的话可以这样:

public async Task<List<UserItem>> GetUserListAsync(string key){List<UserItem> result = new List<UserItem>();var conn = DbContext.Instance.GetDbConnectionAsync();result = await conn.Table<UserItem>().Where(x => x.UserName.Contains(key)).ToListAsync();return result;}

 


 

其他几个Update和Delete也有相应的异步方法,就不写了。

还有几个方法是QueryAsync、ExecuteAsync、ExecuteScalarAsync等等,都可以直接执行sql语句,例如:

public async Task<int> GetUserCount(){var conn = DbContext.Instance.GetDbConnectionAsync();return await conn.ExecuteScalarAsync<int>("select count(*) from UserItem");}

 


 

建议使用异步的方式以获得更好的性能。