更新Azure存储表检索实体时遇“指定资源不存在”错误求助

查询Azure存储表获取实体集合，将实体传入业务方法修改属性后，调用UpdateEntityAsync存回表时抛出异常："The specified resource does not exist"；调用AddEntityAsync则返回409异常："The specified entity already exists"。未修改ETag，无法理解问题原因。

检索实体代码 #

public async Task<IReadOnlyCollection<Message>> GetUndeliveredAsync()
{
    const int maxResultsPerPage = 100;
    IEnumerable<string>? selectProps = null;
    var results = new List<Message>();

    var tableClient = _tableService.GetTableClient();

    var queryResults = tableClient.QueryAsync<Message>($"{nameof(Message.IsDelivered)} eq false and {nameof(Message.FailureCount)} lt {MaxFailureCount}",
                                                           maxResultsPerPage,
                                                           selectProps,
                                                           CancellationToken.None);

    await foreach (var queryResult in queryResults)
    {
        results.Add(queryResult);
    }

    return results;
}

处理并更新实体的方法 #

public async Task AttemptDeliveryAndRecordAsync(Message message)
{
    // ... some business logic...

    // Dispatch the message.
    var dispatchResponse = await _dispatcher.AttemptDeliveryAsync(message, remoteUri);

    // Record whether successful.
    message.IsDelivered = dispatchResponse.IsSuccessful;
    message.LastFailureReason = dispatchResponse.FailureReason;

    // If unsuccessful, update the FailureCount property.
    if (!message.IsDelivered)
    {
        message.IncrementFailureCount(); // Increases an int property by 1.
    }

    // Store the updated Message object.
    await _tableService.UpdateTableEntityAsync(message);
}

更新存储表代码 #

public async Task UpdateTableEntityAsync(ITableEntity tableEntity)
{
    var tableClient = GetTableClient();

    try
    {
        await tableClient.UpdateEntityAsync(tableEntity, ETag.All, TableUpdateMode.Replace);
    }
    catch (Exception exception)
    {
        throw new Exception($"Unable to update {tableEntity.GetType().Name}: {exception.Message}");
    }
}

更新补充：实体类定义 #

实际存储和待更新的是继承自Message的InternalMessage类（实现ITableEntity接口），初始存储成功，但更新失败：

public class InternalMessage : Message, ITableEntity
{
    // Default constructor, required for JSON deserialisation.
    public InternalMessage()
    {
    }

    public InternalMessage(Message message, string remoteUri)
    {
        foreach (var propInfo in message.GetType().GetProperties(System.Reflection.BindingFlags.Instance|System.Reflection.BindingFlags.Public))
        {
            propInfo.SetValue(this, propInfo.GetValue(message));
        }

        RemoteUri = remoteUri;
    }

    public ETag ETag { get; set; }

    public int FailureCount { get; set; } = default;

    public bool IsDelivered { get; set; } = default;

    public string? LastFailureReason { get; set; } = default;

    public string PartitionKey
    {
        get => ProjectId.ToString();
        set
        {
            if (!Guid.TryParse(value, out var projectId))
            {
                throw new ArgumentException($"Invalid value for {nameof(InternalMessage)}.{nameof(PartitionKey)}: {value}.");
            }

            ProjectId = projectId;
        }
    }

    public string? RemoteUri { get; set; }

    public string RowKey
    {
        get => HttpUtility.UrlEncode(Status);
        set => Status = value;
    }

    public DateTimeOffset? Timestamp { get; set; } = default!;

    public void IncrementFailureCount()
    {
        FailureCount++;
    }

    public Message ToMessage()
    {
        var message = new Message();

        foreach (var propInfo in message.GetType().GetProperties(System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.Public))
        {
            propInfo.SetValue(message, propInfo.GetValue(this));
        }

        return message;
    }
}

public class Message
{
    public Message()
    {
        OccurredOn = DateTime.UtcNow;
    }

    public Guid ProjectId { get; set; }

    public string Status { get; set; }

    public DateTime OccurredOn { get; set; }

    public string Username { get; set; }
}

问题根源 #

1. 类型不匹配导致键值不一致：
   检索时使用QueryAsync<Message>，但实际存储的是InternalMessage。Message未实现ITableEntity，查询返回的对象不会包含InternalMessage中RowKey的UrlEncode处理逻辑——表中存储的RowKey是编码后的Status值，但更新时传递的Message对象的RowKey（转换后）是原始未编码值，导致Azure找不到对应实体。

2. 实体转换丢失关键属性：
   InternalMessage转换为Message时，丢失了ETag、PartitionKey、RowKey等ITableEntity接口必需的属性，即使强制转换为ITableEntity，这些属性也无正确值，更新请求自然失败。

解决方案 #

1. 统一实体类型：
   检索时直接查询InternalMessage类型，确保返回实体包含完整的ITableEntity属性：

   public async Task<IReadOnlyCollection<InternalMessage>> GetUndeliveredAsync()
   {
       const int maxResultsPerPage = 100;
       IEnumerable<string>? selectProps = null;
       var results = new List<InternalMessage>();
   
       var tableClient = _tableService.GetTableClient();
   
       var queryResults = tableClient.QueryAsync<InternalMessage>($"{nameof(InternalMessage.IsDelivered)} eq false and {nameof(InternalMessage.FailureCount)} lt {MaxFailureCount}",
                                                               maxResultsPerPage,
                                                               selectProps,
                                                               CancellationToken.None);
   
       await foreach (var queryResult in queryResults)
       {
           results.Add(queryResult);
       }
   
       return results;
   }
   

   同时修改业务方法参数类型为InternalMessage，避免类型转换：

   public async Task AttemptDeliveryAndRecordAsync(InternalMessage message)
   {
       // ... 业务逻辑直接修改message属性
       await _tableService.UpdateTableEntityAsync(message);
   }
   

2. 保留键值处理一致性：
   确保更新时使用的实体，其PartitionKey和RowKey的生成逻辑与存储时完全一致（特别是RowKey的UrlEncode处理）。

3. 维护ETag完整性：
   若需乐观并发控制，更新时传递实体自身的ETag而非ETag.All：

   await tableClient.UpdateEntityAsync(tableEntity, tableEntity.ETag, TableUpdateMode.Replace);
   

内容的提问来源于stack exchange，提问作者awj