c＃-在Web API中返回JPEG，无法删除文件，因为该文件正在被另一个进程使用

Question

I am trying to retrieve a image from the file system and pass it's content through a HttpResponseMessage and then delete the image after. I can get the response to pass the image succesfully but cannot delete it because of the error:

The process cannot access the file 'C:...\\Temp\\c8530aae-ae92-49f3-8f62-cd1f5467fe8a1.jpeg' because it is being used by another process.

My controller code:

 {
   Image returnImg = Image.FromFile(@"C:\...\Temp\" + id + "1" + ".jpeg");
   MemoryStream memoryStream = new MemoryStream();
   returnImg.Save(memoryStream, ImageFormat.Jpeg);

   var message = new HttpResponseMessage(HttpStatusCode.OK)
   {
      Content = new ByteArrayContent(memoryStream.ToArray())
   };
   message.Content.Headers.ContentType = new MediaTypeHeaderValue("image/jpeg");
   File.Delete(@"C:\...\Temp\" + id + "1" + ".jpeg"); //error is on this line execution
   return message
 }

I figure it has something to do with the memory stream, is there a close operation I am missing?

Answer 1

The Image object returnImg implements the IDisposable interface. You will have to place it in a using {} block. Also, MemoryStream is not closed properly.

When a class implements IDisposable class and you are creating an instance of the class you are supposed to wrap it in a using block, so the class can destroy the object properly.Try:

  {
       using(Image returnImg = Image.FromFile(@"C:\...\Temp\" + id + "1" + ".jpeg"))
       {
       using(MemoryStream memoryStream = new MemoryStream())
       {
       returnImg.Save(memoryStream, ImageFormat.Jpeg);

       var message = new HttpResponseMessage(HttpStatusCode.OK)
       {
          Content = new ByteArrayContent(memoryStream.ToArray())
       };
}
       message.Content.Headers.ContentType = new MediaTypeHeaderValue("image/jpeg");
}
       File.Delete(@"C:\...\Temp\" + id + "1" + ".jpeg"); //error is on this line execution
       return message
     }