c＃Linq表达式用多个等待替换foreach答案

【问题标题】：c# Linq expression to replace foreach with multiple awaitsc＃Linq表达式用多个等待替换foreach
【发布时间】：2023-02-03 14:12:27
【问题描述】：

我试图确定是否存在与下面的 foreach 语句等效的 linq 表达式？

我尝试过的几种解决方案中有两种在循环下方对其结果进行了评论。我认为第一个示例或变体会起作用，但类型始终是 IEnumerable<Task> 除非我同步调用它，这让人感到担忧。

public async Task<IEnumerable<CompanySettings>> GetClientSettingsAsync()
{
    foreach(var company in await GetParticipatingCompaniesAsync())
    {
        settings.Add(new CompanySettings(company, await GetSyncDataAsync(company)));
    }

    // a's Type is IEnumerable<Task<CompanySetting>> and not IEnumerable<CompanySetting>
    // var a = (await GetParticipatingCompaniesAsync()).Select(async x => new CompanySettings(x, await GetSyncDataAsync(x)));
    // return a;


    // b's Type is correct it's also synchronous.  Does that matter?
    // var b = (GetParticipatingCompaniesAsync()).Result.Select(x => new CompanySettings(x, GetSyncDataAsync(x).Result));
    //return b;

    return settings;
}

【问题讨论】：

标签： c# linq async-await

【解决方案1】：

您的第一次尝试已经接近尾声，您只需要等待返回的任务

async Task<IEnumerable<CompanySettings>> GetClientSettingsAsync() {

    var companies = await GetParticipatingCompaniesAsync();
    var companySettings = companies.Select(async company =>
        new CompanySettings(company, await GetSyncDataAsync(company))
    );

    return await Task.WhenAll(companySettings);
}

【讨论】：