/// <summary>
/// Read a single table entry from the storage table.
/// </summary>
/// <param name="partitionKey">The partition key for the entry.</param>
/// <param name="rowKey">The row key for the entry.</param>
/// <returns>Value promise for tuple containing the data entry and its corresponding etag.</returns>
public async Task <Tuple <T, string> > ReadSingleTableEntryAsync(string partitionKey, string rowKey)
{
const string operation = "ReadSingleTableEntryAsync";
var startTime = DateTime.UtcNow;
if (Logger.IsVerbose2)
{
Logger.Verbose2("{0} table {1} partitionKey {2} rowKey = {3}", operation, TableName, partitionKey, rowKey);
}
try
{
TableResult retrievedResult = await Task <TableResult> .Factory.FromAsync(
tableReference.BeginExecute,
tableReference.EndExecute,
TableOperation.Retrieve <T>(partitionKey, rowKey),
null);
if (retrievedResult == null || retrievedResult.Result == null || AzureStorageUtils.IsNotFoundError((HttpStatusCode)retrievedResult.HttpStatusCode))
{
if (Logger.IsVerbose)
{
Logger.Verbose("Could not find table entry for PartitionKey={0} RowKey={1}", partitionKey, rowKey);
}
return(null); // No data
}
//The ETag of data is needed in further operations.
return(new Tuple <T, string>(retrievedResult.Result as T, retrievedResult.Etag));
}
finally
{
CheckAlertSlowAccess(startTime, operation);
}
}
/// <summary>
/// Inspect an exception returned from Azure storage libraries to check whether it means that attempt was made to read some data that does not exist in storage table.
/// </summary>
/// <param name="exc">Exception that was returned by Azure storage library operation</param>
/// <returns><c>True</c> if this exception means the data being read was not present in Azure table storage</returns>
public static bool TableStorageDataNotFound(Exception exc)
{
HttpStatusCode httpStatusCode;
string restStatus;
if (AzureStorageUtils.EvaluateException(exc, out httpStatusCode, out restStatus, true))
{
if (AzureStorageUtils.IsNotFoundError(httpStatusCode)
/* New table: Azure table schema not yet initialized, so need to do first create */)
{
return(true);
}
return(StorageErrorCodeStrings.ResourceNotFound.Equals(restStatus));
}
return(false);
}
