关闭c#应用程序后删除DLL

Question

I Have ac# application that include various esternal DLL. When the application start, dlls are exctracted in the .exe folder to grant the correct execution. here the code:

var executingAssembly = Assembly.GetExecutingAssembly();

string folderName = string.Format("{0}.Resources.DLLs", executingAssembly.GetName().Name);
var list = executingAssembly
.GetManifestResourceNames()
.ToArray();
foreach (var item in list)
{
    File.WriteAllBytes(item.Replace("myapp.DLLs.", ""), 
    ReadAllBytes(executingAssembly.GetManifestResourceStream(item)));
}

when i close the form, i want to delete those files with this code, associated to the form closing event:

private void CleanFiles(Object sender, FormClosingEventArgs e)
{
    var executingAssembly = Assembly.GetExecutingAssembly();
    string folderName = string.Format("{0}.Resources.DLLs", executingAssembly.GetName().Name);
    string folder = System.IO.Path.GetDirectoryName(System.Reflection.Assembly.GetEntryAssembly().Location);
    var list = executingAssembly
    .GetManifestResourceNames()
    .ToArray();
    foreach (var item in list)
    {

        File.Delete(folder + @"\" + item.Replace("myapp.DLLs.", ""));
    }
}

If I open and then close the form, it works perfectly. But, if I open the form, do some operations, it throw an exception during the closing operations because access to dlls is denied. How can I release all dlls/resources?

Answer 1

I assume that if you copy these DLLs, you load and use them afterwards.

There's a slight issue with dynamically loading DLLs, being that you can't just unload them. Once loaded into your application domain, they're here to stay.

The solution is thus to simply create a new application domain, load the DLL inside of it, and when you're done, unload this new application domain.

Something like:

var dynamicDomain = AppDomain.CreateDomain("YourDomainName");
var dynamicallyLoadedAssembly = dynamicDomain.Load("YourAssembly");

// do stuff with your dynamically loaded assembly

AppDomain.Unload(dynamicDomain);

For more information on the topic: MSDN "How to: Load and unload assemblies" .

Answer 2

You can (and should) implement exception handling around the parts where you manipulate files on the system:

try
{
  // Manipulate your files here.
}
catch (Exception ex)
{
  // Handle exceptions here. you can also delete the dlls here if you wish.
  // Remember to check in CleanFiles if the files are already deleted.
}
finally
{
  // You could also get rid of the files here.
  // Finally-block is executed regardless if an exception was thrown or not.
}

Usefull links: Microsoft: Exception Handling , Microsoft: Best Ractices for exceptions