CreateFileAsync將寫入文件寫入磁盤寫入訪問被拒絕或容量不足時會發生什麼

Question

我編寫了一個提供下載文件功能的類，我使用CreateFileAsync創建文件，然後使用WriteBytesAsync寫入下載的每個字節。如果目標磁盤寫入被拒絕或容量不足，WriteBytesAsync或CreateFileAsync是否會引發異常？

謝謝。

Answer 1

如果磁盤被寫保護，則可以在創建文件時生成UnauthorizedAccessException。我建議你檢查磁盤驅動器中是否有空閒空間。使用下面給出的方法來獲得磁盤驅動器的空閒容量&。

public static class StorageItemExtensions 
{ 
    public static async Task<IDictionary<string, object>> GetSpace(this IStorageItem sf) 
    { 
     var properties = await sf.GetBasicPropertiesAsync(); 
     return await properties.RetrievePropertiesAsync(new[] { "System.FreeSpace", "System.Capacity" }); 
    } 

    public static string GetSizeString(this ulong sizeInB, double promoteLimit = 1024, double decimalLimit = 10, string separator = " ") 
    { 
     if (sizeInB < promoteLimit) 
      return string.Format("{0}{1}B", sizeInB, separator); 

     var sizeInKB = sizeInB/1024.0; 

     if (sizeInKB < decimalLimit) 
      return string.Format("{0:F2}{1}KB", sizeInKB, separator); 

     if (sizeInKB < promoteLimit) 
      return string.Format("{0:F2}{1}KB", sizeInKB, separator); 

     var sizeInMB = sizeInKB/1024.0; 

     if (sizeInMB < decimalLimit) 
      return string.Format("{0:F2}{1}MB", sizeInMB, separator); 

     if (sizeInMB < promoteLimit) 
      return string.Format("{0:F2}{1}MB", sizeInMB, separator); 

     var sizeInGB = sizeInMB/1024.0; 

     if (sizeInGB < decimalLimit) 
      return string.Format("{0:F2}{1}GB", sizeInGB, separator); 

     if (sizeInGB < promoteLimit) 
      return string.Format("{0:F2}{1}GB", sizeInGB, separator); 

     var sizeInTB = sizeInGB/1024.0; 

     if (sizeInTB < decimalLimit) 
      return string.Format("{0:F2}{1}TB", sizeInTB, separator); 

     return string.Format("{0:F2}{1}TB", sizeInTB, separator); 
    } 
} 

用法：

var filteredProperties = await ApplicationData.Current.LocalFolder.GetSpace(); 
var diskSpace = ((UInt64)filteredProperties["System.FreeSpace"]).GetSizeString() + "/" + ((UInt64)filteredProperties["System.Capacity"]).GetSizeString();