Question

创建新的cosmos DB时，Azure中会显示一些代码示例。大多数代码都能正常工作。但是我有一个单一的函数，它在执行时会冻结/挂起。有什么想法如何解决或排除故障吗？

代码：

public async Task<IEnumerable<T>> GetItemsAsync(Expression<Func<T, bool>> predicate, string collection)
{
    IDocumentQuery<T> query = Client.CreateDocumentQuery<T>(
        UriFactory.CreateDocumentCollectionUri(DatabaseId, collection),
        new FeedOptions { MaxItemCount = -1, EnableCrossPartitionQuery = true })
        .Where(predicate)
        .AsDocumentQuery();

    List<T> results = new List<T>();
    while (query.HasMoreResults)
    {
        try
        {
            var result = await query.ExecuteNextAsync<T>();
            results.AddRange(result);
        }
        catch(Exception ex)
        {

        }
    }

    return results;
}

调用函数：

return await ItemsRepo.GetItemsAsync(p=>p.RunId == runId, "files-and-folders-with-unique-permissions");

最后是Windows应用：

var items = _db.GetFilesAndFoldersWithUniquePermissions(txtRunId.Text).Result;

完整代码：

存储库：

public async Task<IEnumerable<Item>> GetFilesAndFoldersWithUniquePermissions(string runId)
    {
        var collectionLink = UriFactory.CreateDocumentCollectionUri("kk-governance-reporting", "files-and-folders-with-unique-permissions");
        return await ItemsRepo.GetItemsAsync(p=>p.RunId == runId, "files-and-folders-with-unique-permissions");
    }

应用程序：

private void BtnGenerateReport_Click(object sender, EventArgs e)
    {
        var items = _db.GetFilesAndFoldersWithUniquePermissions(txtRunId.Text).Result;

        string json = JsonConvert.SerializeObject(items.ToArray());
        json = JToken.Parse(json).ToString(Formatting.Indented);

        //write string to file
        System.IO.File.WriteAllText(@"c:\temp\unique-files-and-folders.txt", json);

        MessageBox.Show("Completed");
    }

Answer 1

混合 async-await 和.Result阻止调用会导致死锁。

在这种情况下，事件处理程序允许使用async void。

引用Async/Await - Best Practices in Asynchronous Programming

所以我建议您将应用重构以在事件处理程序中等待

private async void BtnGenerateReport_Click(object sender, EventArgs e) {
    var items = await _db.GetFilesAndFoldersWithUniquePermissions(txtRunId.Text); //<-- 

    string json = JsonConvert.SerializeObject(items.ToArray());
    json = JToken.Parse(json).ToString(Formatting.Indented);

    //write string to file
    System.IO.File.WriteAllText(@"c:\temp\unique-files-and-folders.txt", json);

    MessageBox.Show("Completed");
}

以使代码按预期方式流动。

ExecuteNextAsync冻结/挂起Azure Cosmos DB

1 个答案: