[C#] Looping all keys of Dictionary

void Main()
{
// define a dictionary                  
Dictionary<string, bool> selectedLayers = new Dictionary<string, bool>();
       
// add items to dictionary
for (int i = 0; i < 10; ++i)
{
   selectedLayers.Add(i.ToString(), true);
}

// looping all items of dictionary
foreach(var num in selectedLayers.Keys)
{
   Console.WriteLine(num);
}
}