5. 文件下载¶

NOS C# SDK提供了丰富的文件下载接口，用户可以通过以下方式从NOS获取文件:

下载文件到内存
下载到本地文件
分段下载
条件下载

5.1. 下载文件到内存¶

以下源代码实现下载文件到内存中:

// 初始化NosClient
var nosClient = new NosClient(endpoint, accessKeyId, accessKeySecret);

/// <summary>
/// 下载文件到内存
/// </summary>
/// <param name="bucket">桶名</param>
/// <param name="bucket">对象名</param>
public void GetObject(string bucket, string key)
{
    try
    {
        var result = nosClient.GetObject(bucket, key);
        Console.WriteLine(result.Content);

        Console.WriteLine("Get object succeeded");
    }
    catch (NosException ex)
    {
        Console.WriteLine("Failed with HTTPStatus: {0}; \nErrorCode: {1}; \nErrorMessage: {2}; \nRequestID:{3}; \nResource:{4}",
                ex.StatusCode, ex.ErrorCode, ex.Message, ex.RequestId, ex.Resource);
    }
    catch (Exception ex)
    {
        Console.WriteLine("Failed with error info: {0}", ex.Message);
    }
}

5.2. 下载文件到本地文件¶

以下源代码实现将NOS文件下载到本地文件:

// 初始化NosClient
var nosClient = new NosClient(endpoint, accessKeyId, accessKeySecret);

/// <summary>
/// 下载文件到本地
/// </summary>
/// <param name="bucket">桶名</param>
/// <param name="bucket">对象名</param>
/// <param name="bucket">下载到的本地文件</param>
public void GetObject(string bucket, string key, string fileToDownload)
{
    try
    {
        nosClient.GetObject(bucket, key, fileToDownload);

        Console.WriteLine("Get object succeeded");
    }
    catch (NosException ex)
    {
        Console.WriteLine("Failed with HTTPStatus: {0}; \nErrorCode: {1}; \nErrorMessage: {2}; \nRequestID:{3}; \nResource:{4}",
                ex.StatusCode, ex.ErrorCode, ex.Message, ex.RequestId, ex.Resource);
    }
    catch (Exception ex)
    {
        Console.WriteLine("Failed with error info: {0}", ex.Message);
    }
}

5.3. 指定范围下载¶

如果存储在NOS中的文件较大，并且您只需要其中的一部分内容，您可以使用范围下载，下载指定范围的数据，如果指定的下载范围为”0-100”，则返回结果为第0字节到第100字节的数据，返回的数据包含第100字节，即range=0-100，如果指定的范围无效则下载整个文件，以下源代码获取range=0-100字节的内容:

// 初始化NosClient
var nosClient = new NosClient(endpoint, accessKeyId, accessKeySecret);

/// <summary>
/// 指定范围下载
/// </summary>
/// <param name="bucket">桶名</param>
/// <param name="bucket">对象名</param>
/// <param name="bucket">下载到的本地文件</param>
public void GetObject(string bucketName, string key, string fileToDownload)
{
    try
    {
        var request = new GetObjectRequest(bucketName, key);
        request.Range = "bytes=0-100";
        var result = nosClient.GetObject(request,fileToDownload);

        Console.WriteLine("Get object succeeded");
    }
    catch (NosException ex)
    {
        Console.WriteLine("Failed with HTTPStatus: {0}; \nErrorCode: {1}; \nErrorMessage: {2}; \nRequestID:{3}; \nResource:{4}",
                ex.StatusCode, ex.ErrorCode, ex.Message, ex.RequestId, ex.Resource);
    }
    catch (Exception ex)
    {
        Console.WriteLine("Failed with error info: {0}", ex.Message);
    }
}

Attention

下载内容也可以存储到文件中
注意下载的区间为闭区间

5.4. 条件下载¶

下载文件时，可以指定限定条件，满足限定条件时下载，不满足时报错，不下载文件。可以使用的限定条件如下：

参数	说明	GetObjectRequest对应值
If-Modified-Since	如果指定的时间早于实际修改时间，则正常传送。否则返回错误	GetObjectRequest.IfModifiedSince

// 初始化NosClient
var nosClient = new NosClient(endpoint, accessKeyId, accessKeySecret);

/// <summary>
/// 指定条件下载
/// </summary>
/// <param name="bucket">桶名</param>
/// <param name="bucket">对象名</param>
/// <param name="bucket">下载到的本地文件</param>
public void GetObject(string bucketName, string key, string fileToDownload)
{
    try
    {
        var request = new GetObjectRequest(bucketName, key);
        request.If-Modified-Since = "Fri, 13 Nov 2016 14:47:53 GMT";
        var result = nosClient.GetObject(request,fileToDownload);

        Console.WriteLine("Get object succeeded");
    }
    catch (NosException ex)
    {
        Console.WriteLine("Failed with HTTPStatus: {0}; \nErrorCode: {1}; \nErrorMessage: {2}; \nRequestID:{3}; \nResource:{4}",
                ex.StatusCode, ex.ErrorCode, ex.Message, ex.RequestId, ex.Resource);
    }
    catch (Exception ex)
    {
        Console.WriteLine("Failed with error info: {0}", ex.Message);
    }
}

Attention

下载内容也可以存储到文件中