c# - 无法从表存储中获取记录

Question

我有一个表存储表，我想从中获取一些数据。插入和更新查询工作正常，但当我尝试选择一些记录时遇到问题。下面是我到目前为止所做的代码:

class TransactionEntity : TableEntity
{
    public String s{ get; set; }
    public Int32 r { get; set; }
    public String e{ get; set; }
    public String t{ get; set; }
    public String l{ get; set; }
    public TransactionEntity(String id, String s, String e, String t)
    {
        this.r= 0;
        this.s= s;
        this.RowKey = id;
        this.PartitionKey = Guid.NewGuid().ToString();
        this.e= e == null ? "" : e;
        this.t= t== null ? "" : t;
    }
}

管理表的代码:

class TableStorageManager
{
    public Boolean AddTransaction(TransactionEntity dto)
    {
        try
        {
            // Create the table client.
            CloudTableClient tableClient = new CloudTableClient(new System.Uri(ConfigurationManager.AppSettings.Get("TableStorageURI")), new StorageCredentials(ConfigurationManager.AppSettings.Get("TableStorageUser"), ConfigurationManager.AppSettings.Get("TableStoragePassword")));
            CloudTable table = tableClient.GetTableReference(ConfigurationManager.AppSettings.Get("TableStorageName"));
            table.CreateIfNotExists();
            TableOperation op = TableOperation.Insert(dto);    
            table.Execute(op);    
            return true;
        }
        catch (Exception ex)
        {
            return false;
        }
    }

    public List<TransactionEntity> RetrieveAllFailedTransactions()
    {
        try
        {
            CloudTableClient tableClient = new CloudTableClient(new System.Uri(ConfigurationManager.AppSettings.Get("TableStorageURI")), new StorageCredentials(ConfigurationManager.AppSettings.Get("TableStorageUser"), ConfigurationManager.AppSettings.Get("TableStoragePassword")));
            CloudTable table = tableClient.GetTableReference(ConfigurationManager.AppSettings.Get("TableStorageName"));         
            TableQuery<TransactionEntity> query = new TableQuery<TransactionEntity>().Where("s eq '" + ConfigurationManager.AppSettings.Get("E") + "' and r lt " + ConfigurationManager.AppSettings.Get("M") + "");
            query.Take(ConfigurationTasks.GetResultLength());  
            return table.ExecuteQuery(query).ToList();
        }
        catch (Exception ex)
        {
            return null;
        }
    }

    public Boolean UpdateTransactionStatus(TransactionEntity dto)
    {
        try
        {                    
            CloudTableClient tableClient = new CloudTableClient(new System.Uri(ConfigurationManager.AppSettings.Get("TableStorageURI")), new StorageCredentials(ConfigurationManager.AppSettings.Get("TableStorageUser"), ConfigurationManager.AppSettings.Get("TableStoragePassword")));                   
            CloudTable table = tableClient.GetTableReference(ConfigurationManager.AppSettings.Get("TableStorageName"));
            dto.ETag = "*";
            TableOperation op = TableOperation.Replace(dto);
            table.Execute(op);    
            return true;
        }
        catch (Exception ex)
        {
            return false;
        }
    }
}

此外，我还更改了变量名称，如果你们在阅读它们时遇到一些麻烦，我很抱歉。

Answer 1

我相信继承 TableEntity 的类中可能缺少默认/无参数构造函数。当从 TableStorage 接收对象时，非常需要无参数构造函数来反序列化对象。

因此，将您的 TableEntity 代码更改为:

class TransactionEntity : TableEntity
{
    public String s{ get; set; }
    public Int32 r { get; set; }
    public String e{ get; set; }
    public String t{ get; set; }
    public String l{ get; set; }
    public TransactionEntity(){//do nothing}
    public TransactionEntity(String id, String s, String e, String t)
    {
        this.r= 0;
        this.s= s;
        this.RowKey = id;
        this.PartitionKey = Guid.NewGuid().ToString();
        this.e= e == null ? "" : e;
        this.t= t== null ? "" : t;
    }
}

尽管我仍然相信，如果您能分享有关运行代码时遇到的任何异常的更多详细信息，那就太好了。 另请参阅this link更好地解释如何使用 TableStorage。