**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

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);
        }
    }


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);
        }
    }


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::

	1. 下载内容也可以存储到文件中
	2. 注意下载的区间为闭区间


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::

	1. 下载内容也可以存储到文件中