Question

当我尝试清除可观察的收藏集时，它崩溃了。另一种清除它的方法？

ObservableCollection<Group> _groupList = new ObservableCollection<Group>();
public ObservableCollection<Group> GroupList
{
    get
    {
        return _groupList;
    }

    set
    {
        _groupList = value;
        RaisePropertyChanged("GroupList"); 
    }
}

Answer 1

您可以简单地创建一个新集合：

// for the purpose of this question i've reduced the array to 5 files!
$uris = array /
  "https://cdn.enchufix.com/media/catalog/product/u/n/unix-48120.jpg",
  "https://cdn.enchufix.com/media/catalog/product/u/n/unix-48120-01.jpg",
  "https://cdn.enchufix.com/media/catalog/product/u/n/unix-48120-02.jpg",
  "https://cdn.enchufix.com/media/catalog/product/u/n/unix-48120-03.jpg",
  "https://cdn.enchufix.com/media/catalog/product/u/n/unix-48120-04.jpg",
);

function downloadFilesAsync2(array $uris, string $dir, $overwrite=true) {
    $client   = new \GuzzleHttp\Client();
    $requests = array();
    foreach ($uris as $i => $uri) {
        $loc = $dir . DIRECTORY_SEPARATOR . basename($uri);
        if ($overwrite && file_exists($loc)) unlink($loc);
        $requests[] = new GuzzleHttp\Psr7\Request('GET', $uri, ['sink' => $loc]);
        echo "Downloading $uri to $loc" . PHP_EOL;
    }
    $pool = new \GuzzleHttp\Pool($client, $requests, [
        'concurrency' => 10,
        'fulfilled' => function (\Psr\Http\Message\ResponseInterface $response, $index) {
            // this is delivered each successful response
            echo 'success: '.$response->getStatusCode().PHP_EOL;
        },
        'rejected' => function ($reason, $index) {
            // this is delivered each failed request
            echo 'failed: '.$reason.PHP_EOL;
        },
    ]);
    $promise = $pool->promise();  // Start transfers and create a promise
    $promise->wait();   // Force the pool of requests to complete.
}

function downloadFilesAsync1(array $uris, string $dir, $overwrite=true) {
    $client = new \GuzzleHttp\Client();
    $promises = (function () use ($client, $uris, $dir, $overwrite) {
        foreach ($uris as $uri) {
            $loc = $dir . DIRECTORY_SEPARATOR . basename($uri);
            if ($overwrite && file_exists($loc)) unlink($loc);
            yield $client->requestAsync('GET', $uri, ['sink' => $loc]);
            echo "Downloading $uri to $loc" . PHP_EOL;
        }
    })();
    (new \GuzzleHttp\Promise\EachPromise(
        $promises, [
        'concurrency' => 10,
        'fulfilled'   => function (\Psr\Http\Message\ResponseInterface $response) {
            //            echo "\t=>\tDONE! status:" . $response->getStatusCode() . PHP_EOL;
        },
        'rejected'    => function ($reason, $index) {
            echo 'ERROR => ' . strtok($reason->getMessage(), "\n") . PHP_EOL;
        },
    ])
    )->promise()->wait();
}

Answer 2

有一个清晰的功能

GroupList.Clear();

或

 GroupList = new ObservableCollection<Group>();

也可以尝试声明您以这种方式列出：

ObservableCollection<Group> _groupList;
public ObservableCollection<Group> GroupList
{
    get { return _groupList; }
    set { SetValue(ref _groupList, value); }
}

如何在不使用清除方法的情况下清除可观察的集合

2 个答案: