进行并行api调用并在c＃中异步处理每个响应

Question

我有一个场景，我需要在c＃（Xamarin iOS和Xamarin Android）中并行地进行多个api调用（具有不同参数的相同api）。而且我不想等待所有任务完成，相反，无论何时响应，我都应该处理它并相应地更新UI。

需要多次调用的方法

public  async Task<Response> GetProductsAsync(int categoryId, int pageNo = -1, int pageSize = -1)
        {
            try
            {
                string url = "";
                if (pageNo == -1 || pageSize == -1)
                    url = $"catalog/v1/categories/{categoryId}/products";
                else
                    url = $"catalog/v1/categories/{categoryId}/products?page-number={pageNo}&page-size={pageSize}";
                var response = await client.GetAsync(url);
                string responseString = await response.Content.ReadAsStringAsync();
                GetParsedData(response.IsSuccessStatusCode, responseString);
            }
            catch (Exception e)
            {
                apiResponse.status = "internalError";
                apiResponse.data = e.Message;
            }
            return apiResponse;
        }

Answer 1

从调用函数您可以编写如下代码

    public void CallingFunctionToGetProductsAsync() {
        Task.Run(async () =>
        {
            var response = await GetProductsAsync(1);
            ProcessResponse(response);
        });

        Task.Run(async () =>
        {
            var response = await GetProductsAsync(2);
            ProcessResponse(response);
        });
    }

Answer 2

这就是您可以等待多个任务异步并在任何一个完成时更新UI的方法。

async Task GetSomeProductsAsync( IEnumerable<int> categoryIds )
{
    List<Task<Response>> tasks = categoryIds
        .Select( catId => GetProductsAsync( catId ) )
        .ToList();

    while ( tasks.Any() )
    {
        var completed = await Task.WhenAny( tasks );
        tasks.Remove( completed );
        var response = completed.Result;
        // update the ui from this response
    }
}

作为旁注：

您应该将ConfigureAwait(false)添加到GetProducsAsync中等待代码中，以避免与调用者线程无法同步（这将是UI）

public  async Task<Response> GetProductsAsync(int categoryId, int pageNo = -1, int pageSize = -1)
{
    try
    {
        string url = "";
        if (pageNo == -1 || pageSize == -1)
            url = $"catalog/v1/categories/{categoryId}/products";
        else
            url = $"catalog/v1/categories/{categoryId}/products?page-number={pageNo}&page-size={pageSize}";
        var response = await client.GetAsync(url).ConfigureAwait(false);
        string responseString = await response.Content.ReadAsStringAsync().ConfigureAwait(false);
        GetParsedData(response.IsSuccessStatusCode, responseString);
    }
    catch (Exception e)
    {
        apiResponse.status = "internalError";
        apiResponse.data = e.Message;
    }
    return apiResponse;
}

您可以在Stephen Cleary的博客文章：Don't block on Async Code中阅读更多相关信息