How Can I Efficiently Unload an Assembly Loaded with Assembly.LoadFrom()?

Unloading Assembly Loaded with Assembly.LoadFrom()

To test the time taken by GetTypes() after loading a DLL, let's explore the process of unloading and reloading the DLL.

Unloading the Assembly

When an assembly is loaded using Assembly.LoadFrom(), it is added to the AppDomain's list of assemblies. To unload it, there is no explicit method in Assembly or AppDomain for unloading. However, you can create a new AppDomain to load the assembly and then unload the AppDomain to release the resources.

Reload and Time Comparison

To reload the DLL, follow these steps:

1. Create a new AppDomain with a different name.
2. Load the assembly into the new AppDomain using AppDomain.Load().
3. Get the time taken by GetTypes() for the reloaded assembly.
4. Unload the AppDomain to release resources.

Example:

string file = "path/to/assembly.dll";

// First AppDomain
AppDomain dom1 = AppDomain.CreateDomain("domain1");
Assembly assem1 = dom1.Load(file);
Stopwatch sw1 = Stopwatch.StartNew();
var types1 = assem1.GetTypes();
sw1.Stop();
double time1 = sw1.Elapsed.TotalMilliseconds;
AppDomain.Unload(dom1);

// Second AppDomain
AppDomain dom2 = AppDomain.CreateDomain("domain2");
Assembly assem2 = dom2.Load(file);
Stopwatch sw2 = Stopwatch.StartNew();
var types2 = assem2.GetTypes();
sw2.Stop();
double time2 = sw2.Elapsed.TotalMilliseconds;
AppDomain.Unload(dom2);

Console.WriteLine($"First Load: {time1} milliseconds");
Console.WriteLine($"Second Load: {time2} milliseconds");

This example creates two AppDomains and loads the DLL into each. It then measures the time taken by GetTypes() for both instances. The difference in timings can indicate the overhead incurred by reloading the DLL.

Explicit Garbage Collection

assem = null is not sufficient to release resources allocated to an Assembly. Explicitly calling the garbage collector will not help either, as AppDomain-specific resources are not managed by it. Using a new AppDomain is the recommended approach for unloading assemblies and releasing their associated resources.

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