question

I created files as per

 string[] names = {
     "Name001.product",
     "Name002.product",
     "Name003.product",
     "Name101.product.prototype",
     "Name102.product.prototype",
     "Name103.product.prototype",
 };
    
 foreach (var name in names)
 {
     File.WriteAllText(name,"");
 }

Then in another event

 Directory.GetFiles(
     AppDomain.CurrentDomain.BaseDirectory,"*.product")
     .ToList()
     .ForEach(Console.WriteLine);
    
 Console.WriteLine();
    
 Directory.GetFiles(
     AppDomain.CurrentDomain.BaseDirectory, 
     "*.product.prototype")
     .ToList()
     .ForEach(Console.WriteLine);

Outputs

C:\Dotnetland\VS2019\ForumQuestion\Demo\bin\Debug\Name001.product
C:\Dotnetland\VS2019\ForumQuestion\Demo\bin\Debug\Name002.product
C:\Dotnetland\VS2019\ForumQuestion\Demo\bin\Debug\Name003.product

C:\Dotnetland\VS2019\ForumQuestion\Demo\bin\Debug\Name101.product.prototype
C:\Dotnetland\VS2019\ForumQuestion\Demo\bin\Debug\Name102.product.prototype
C:\Dotnetland\VS2019\ForumQuestion\Demo\bin\Debug\Name103.product.prototype

I ran the above code with .NET Core 5 and .NET Framework 4.8, both yield the same output.

Another example with a different pattern and predicate.

 Directory.GetFiles(
         AppDomain.CurrentDomain.BaseDirectory, "Name*.*")
     .Where(fileName => !fileName.EndsWith("prototype"))
     .ToList()
     .ForEach(Console.WriteLine);