WPF字節數組映射到ImageSource而不使用MemoryStream

Question

我有一個應用程序可以即時創建WPF圖像控件以顯示來自SQL Server數據庫表的圖像。顯示控件的面板經常被更換。我使用MemoryStreams來允許控件訪問從數據庫加載的字節數組。只要顯示圖像控件並且仍然顯示圖像，我就無法關閉這些流。我擔心的是，這些流將保持開放狀態，直到垃圾收集器開始處理圖像控件並希望關閉流。我可能會最終確定在更換面板之前關閉了流或丟棄了圖像控件，但是想知道是否存在將這些流打開以及是否存在解決方法的問題。

下面是我使用的代碼。

public class ImageToSql 
{ 
    private static OpenFileDialog _openFileDialog = new OpenFileDialog(); 

    static ImageToSql() 
    { 
     _openFileDialog = new OpenFileDialog(); 
     _openFileDialog.AddExtension = true; 
     _openFileDialog.CheckFileExists = true; 
     _openFileDialog.DefaultExt = ".jpg"; 
     _openFileDialog.Filter = "JPEG files (*.jpg)|*.jpg|All files (*.*)|*.*"; 
     _openFileDialog.FilterIndex = 1; 
     _openFileDialog.Multiselect = false; 
    } 

    public static BitmapImage LoadImageFromFile(string caption) 
    { 
     BitmapImage bi = new BitmapImage(); 

     _openFileDialog.Title = caption; 
     if (_openFileDialog.ShowDialog() == true) 
     { 
      bi.BeginInit(); 
      bi.StreamSource = File.OpenRead(_openFileDialog.FileName); 
      bi.EndInit(); 
     } 

     return bi; 
    } 

    public static int StoreImage(string connectionString, string sql, string imageParameterName, BitmapImage bitmapImage) 
    { 
     SqlConnection conn = new SqlConnection(connectionString); 
     try 
     { 
      conn.Open(); 
      sql += ";SELECT @@IDENTITY"; 
      using (SqlCommand cmd = new SqlCommand(sql, conn)) 
      { 
       byte[] data = new byte[bitmapImage.StreamSource.Length]; 
       bitmapImage.StreamSource.Seek(0, SeekOrigin.Begin); 
       bitmapImage.StreamSource.Read(data, 0, data.Length); 

       cmd.Parameters.Add(imageParameterName, System.Data.SqlDbType.VarBinary, -1).Value = data; 
       object obj = cmd.ExecuteScalar(); 
       return Int32.Parse(obj.ToString()); 
      } 
     } 
     finally 
     { 
      conn.Close();     
     } 
    } 

    public static BitmapImage RetrieveImage(string connectionString, string sql, string imageIDParameterName, int imageID) 
    { 
     BitmapImage bi = new BitmapImage(); 
     SqlConnection conn = new SqlConnection(connectionString); 
     try 
     { 
      conn.Open(); 
      using (SqlCommand cmd = new SqlCommand(sql, conn)) 
      { 
       cmd.Parameters.Add(imageIDParameterName, System.Data.SqlDbType.Int).Value = imageID; 
       byte[] data = (byte[])cmd.ExecuteScalar(); 

       MemoryStream ms = new MemoryStream(data); 
       ms.Seek(0, SeekOrigin.Begin); 
       bi.BeginInit(); 
       bi.StreamSource = ms; 
       bi.EndInit(); 
      } 
     } 
     finally 
     { 
      conn.Close(); 
     } 

     return bi; 
    } 
} 

下面是如何調用這段代碼。 「_fileImage」和「_sqlImage」是我測試窗口上的圖像控件。有一次，我使用流在「LoadImageFromFile」中從磁盤讀取文件，並認爲我能夠關閉該流，同時仍然在Image控件中顯示圖像。所以，MemoryStream似乎很特別。

 BitmapImage bi = ImageToSql.LoadImageFromFile("Select Image to Save"); 
     _fileImage.Source = bi; 

     int imageID = ImageToSql.StoreImage(connString, 
      "INSERT INTO PV_Image (Description, Image) VALUES ('Some Image', @pImage)", 
      "@pImage", bi); 

     _sqlImage.Source = ImageToSql.RetrieveImage(connString, 
      "SELECT Image FROM PV_Image WHERE ImageID = @pImageID", 
      "@pImageID", imageID); 

Answer 1

可以處理存儲流一旦使用使用模式中使用：

using (Stream stream = new MemoryStream(data)) 
{ 
    BitmapImage image = new BitmapImage(): 
    stream.Position = 0; 
    image.BeginInit(); 
    image.CacheOption = BitmapCacheOption.OnLoad; 
    image.StreamSource = stream; 
    image.EndInit(); 
    image.Freeze(); 
    return image; 
}