Why do files I have opened remain open unless I Dispose() them?

In my application, I am using OpenFileDialog and then assign the loaded file to LoadedFile field. I have found out that if I open 3 files, all remained open (access denied when trying to do anything with them) and I am not sure why? However when doing this, it wo开发者_JAVA百科rks fine:

if(LoadedFile!=null)
{
  LoadedFile.Dispose();
  LoadedFile=null;
}

LoadedFile=openFileDialog.GetFile() //pseudo code

Is it enough? Why all files remained "open" if I do not do that?

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If you don't explicitly close an open file, it remains open and you get the access violation exception.

You should open the file within a using statement in order to ensure that it is disposed of correctly (which is what your code does, manually).

using(File aFile = File.Open("path to file"))
{
 // use the file
}

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Note:

This has nothing to do with memory (which you don't control yourself, as .NET is garbage collected). It is about resource management, in this case open file handles.

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Until you call Dispose() (i.e., stating that you don't need it any more), the file will be locked.

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You must close a file once you're done with it. Dispose does that.