[dotnet] Add dotnet projects and examples

+ Sitemap generator I created while learning the dispose pattern
+ Testing project for learning general C#

dotnet/testing/KlipsLibrary/Animal.cs

@@ -0,0 +1,70 @@
+using System.Collections;
+using KlipsLibrary;
+namespace KlipsLibrary;
+public class Solution {
+    public int NumUniqueEmails(string[] emails)
+    {
+      HashSet<string> sent = new();
+      foreach (var email in emails)
+      {
+        var domain = email.Substring(email.IndexOf("@"), email.Length);
+        var to = email.Substring(0, email.IndexOf("@"));
+        if (to.Contains(".")) to = to.Replace(".", "");
+        to = to.Remove(to.IndexOf("+"));
+        Console.Write("{0} at {1}", to, domain);
+        sent.Add(to + "@" + domain);
+      }
+
+      return sent.Count;
+    }
+}
+public abstract class Animal
+{
+  public Animal(string n, string p)
+  {
+    this.Name = n;
+    this.Phrase = p;
+  }
+
+  public abstract void Speak();
+
+  private string name;
+  public string Name { get; set; }
+  private string phrase;
+  public string Phrase { get; set; }
+}
+
+public class Dog : Animal
+{
+  public Dog(string n, string p) : base(n, p) { }
+
+  public override void Speak()
+  {
+    Console.WriteLine("{0} (Dog): {1}", Name, Phrase);
+  }
+}
+
+public class Human : Animal
+{
+  public Human(string n, string p) : base(n, p) { }
+
+  public override void Speak()
+  {
+    Console.WriteLine("{0} (Human): {1}", Name, Phrase);
+  }
+}
+
+public class Teacher : Human, IComparable, ICloneable
+{
+  public Teacher(string n, string p) : base(n, p) { }
+
+  public int CompareTo(object? obj)
+  {
+    throw new NotImplementedException();
+  }
+
+  public object Clone()
+  {
+    throw new NotImplementedException();
+  }
+}