DBShadow.net之化繁为简

一、简化查询

1. 先看一下查询的例子

/// <summary>
/// 账户获取服务
/// </summary>
/// <param name="table"></param>
/// <param name="builder"></param>
public class AccountGetService(AccountTable table, IShadowBuilder builder)
{
    private readonly SqlSource _source = new(builder.DataSource);
    private readonly IParamQuery<Account, Account> _accountQuery
        = builder.BuildResult<Account, Account>(
            table.ToQuery()
                .And(account => account.Id.Equal())
                .ToSelect()
                .SelectSelfColumns()
        );
    /// <summary>
    /// 获取账户
    /// </summary>
    /// <param name="param"></param>
    /// <param name="token"></param>
    /// <returns></returns>
    public Task<Account?> GetAsync(Account param, CancellationToken token = default)
        => _accountQuery.GetFirstAsync(_source, param, token);
}

2. 调用方式如下

var account = await accountGetService.GetAsync(new Account { Id = 1L });

3. 这个例子我们可以简化一下

• 参数直接使用Id(类型由Account简化为long)
• 很大一部分数据库操作都只有一个参数(GetById、GetByName等)
• 为此定义一个含单个属性类有点浪费
• 按上面的例子使用实体类作为参数也感觉怪怪的
• DBShadow.net支持这种简化操作
• 单个参数无需封装,直接使用参数类型即可

public class AccountGetService(AccountTable table, IShadowBuilder builder)
{
    private readonly SqlSource _source = new(builder.DataSource);
    private readonly IParamQuery<long, Account> _accountQuery
        = builder.BuildResult<long, Account>(
            table.ToQuery()
                .And(account => account.Id.Equal())
                .ToSelect()
                .SelectSelfColumns()
        );
    public Task<Account?> GetAsync(long accountId, CancellationToken token = default)
        => _accountQuery.GetFirstAsync(_source, param, token);
}
var account = await accountGetService.GetAsync(1L);

4. 特别注意不要在Dapper中这样使用

• Dapper是不支持这种简化操作
• 以下Dapper错误示例会抛出异常
• System.InvalidOperationException:“Must add values for the following parameters: @Id”

await using var conn = _dataSource.CreateConnection();
var sql = "SELECT \"Id\",\"Title\",\"Content\",\"Done\",\"LastTime\" FROM \"Todo\" WHERE \"Id\"=@Id";
var first = await conn.QueryFirstOrDefaultAsync<Todo>(sql, 1L);

二、 集合参数也支持简化操作

1. IN查询简化的例子

• In的参数名是可选和前面例子的Equal是一样的,默认字段名
• In查询的实参支持数组、集合及字典
• 只有In一个集合参数时支持直接传数组、集合或字典
• 这时参数名(eg: AccountIds)就无所谓取什么名了
• 因为不需要按参数名反射获取属性了

/// <summary>
/// 批量账户获取服务
/// </summary>
/// <param name="table"></param>
/// <param name="builder"></param>
public class AccountBatchService(AccountTable table, IShadowBuilder builder)
{
    private readonly SqlSource _source = new(builder.DataSource);
    private readonly IParamQuery<long[], Account> _accountQuery
        = builder.BuildResult<long[], Account>(
            table.ToQuery()
                .And(account => account.Id.In("AccountIds"))
                .ToSelect()
                .SelectSelfColumns()
        );
    /// <summary>
    /// 批量获取账户
    /// </summary>
    /// <param name="accountIds"></param>
    /// <param name="token"></param>
    /// <returns></returns>
    public IAsyncEnumerable<Account> GetAsync(long[] accountIds, CancellationToken token = default)
        => _accountQuery.QueryAsync(_source, accountIds, token);
}

2. 以上调用的例子如下

[Fact]
public async Task Batch()
{
    var count = 0;
    var service = new AccountBatchService(table, builder);
    var list = service.GetAsync([1L, 2L, 3L]);
    await foreach (var item in list)
    {
        _output.WriteLine($"{item.Id}:{item.Amount}");
        count++;
    }
    Assert.Equal(3, count);
}
// 1:100
// 2:200
// 3:300

三、泛型查询

1. 泛型服务类代码

• 该服务用来按字段Id查询表Account
• 参数TParam是泛型,这样可以直接使用DTO参数来查询,减少类型转化的开销
• 返回值TAccount也是泛型,这样就可以直接返回视图模型或者领域模型
• 这样的泛型服务类就非常的通用

/// <summary>
/// 账户获取泛型服务
/// </summary>
/// <param name="table"></param>
/// <param name="builder"></param>
public class AccountGetService<TParam, TAccount>(AccountTable table, IShadowBuilder builder)
{
    private readonly SqlSource _source = new(builder.DataSource);
    private readonly IParamQuery<TParam, TAccount> _accountQuery
        = builder.BuildResult<TParam, TAccount>(
            table.ToQuery()
                .And(account => account.Id.Equal())
                .ToSelect()
                .SelectSelfColumns()
        );
    /// <summary>
    /// 获取账户
    /// </summary>
    /// <param name="param"></param>
    /// <param name="token"></param>
    /// <returns></returns>
    public Task<TAccount?> GetAsync(TParam param, CancellationToken token = default)
        => _accountQuery.GetFirstAsync(_source, param, token);
}

2. 中规中矩的调用方式

var service = new AccountGetService<Account, Account>(_table, _builder);
var account = await service.GetAsync(new Account { Id = 1L });
Assert.NotNull(account);

3. 支持简单调用方式

var service = new AccountGetService<long, Account>(_table, _builder);
var account = await service.GetAsync(1L);
Assert.NotNull(account);

四、总结

• DBShadow.net预编译比较智能
• 只有1个参数时支持化繁为简,支持直接传值做为参数值
• 这样可以节约定义只有一个属性的参数类
• 参数和返回值类型还可以定义为泛型,可以做到更加灵活

另外源码托管地址: https://github.com/donetsoftwork/DBShadow.net ，欢迎大家直接查看源码。
gitee同步更新:https://gitee.com/donetsoftwork/DBShadow.net

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