public async Task <AccountResult> GetAccount(string provider, string subject,
CancellationToken cancellationToken)
{
Ensure.String.IsNotNullOrWhiteSpace(provider, nameof(provider));
Ensure.String.IsNotNullOrWhiteSpace(subject, nameof(subject));
var operation = TableOperation.Retrieve <AccountAdapter>(provider, subject);
var table = GetTable(TableName);
var account = await RetrieveAccount(cancellationToken, table, operation).ConfigureAwait(false);
if (account != null)
{
return(account);
}
try
{
// This account does not yet exist Attempt to create it
var newAccount = new Account
{
Id = Guid.NewGuid(),
Provider = provider,
Subject = subject
};
await RegisterAccount(newAccount, cancellationToken).ConfigureAwait(false);
account = new AccountResult(newAccount)
{
IsNewAccount = true
};
}
catch (StorageException ex)
{
// The account already exists between us trying to get it and create it This logic
// avoids us writing a synchronisation lock here which would slow down the code here
// for a situation which will only happen up to once per account
if (ex.RequestInformation.ExtendedErrorInformation.ErrorCode == "EntityAlreadyExists")
{
// The account already exists from another operation, probably concurrent
// asynchronous calls
return(await RetrieveAccount(cancellationToken, table, operation).ConfigureAwait(false));
}
throw;
}
return(account);
}
protected virtual async Task <AccountResult> RetrieveAccount(CancellationToken cancellationToken,
CloudTable table,
TableOperation operation)
{
var result = await table.ExecuteAsync(operation, null, null, cancellationToken).ConfigureAwait(false);
if (result.HttpStatusCode == 404)
{
return(null);
}
var entity = (AccountAdapter)result.Result;
var account = new AccountResult(entity.Value)
{
IsNewAccount = false
};
return(account);
}
