Change Command abstract class to an interface.

Author: ivandrofly

Command/Command.csproj

@@ -44,7 +44,7 @@
   <ItemGroup>
     <Compile Include="Calculator.cs" />
     <Compile Include="Command\CalculatorCommand.cs" />
-    <Compile Include="Command\Command.cs" />
+    <Compile Include="Command\ICommand.cs" />
     <Compile Include="Program.RealWordCode.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="User.cs" />

Command/Command/CalculatorCommand.cs

@@ -11,7 +11,7 @@ namespace DoFactory.GangOfFour.Command.RealWorld
     /// <summary>
     /// The 'ConcreteCommand' class
     /// </summary>
-    class CalculatorCommand : Command
+    class CalculatorCommand : ICommand
     {
         private char _operator;
         private int _operand;
@@ -39,13 +39,13 @@ public int Operand
         }
 
         // Execute new command
-        public override void Execute()
+        public void Execute()
         {
             _calculator.Operation(_operator, _operand);
         }
 
         // Unexecute last command
-        public override void UnExecute()
+        public void UnExecute()
         {
             _calculator.Operation(Undo(_operator), _operand);
         }

Command/Command/Command.cs Command/Command/ICommand.cs

@@ -8,11 +8,11 @@ namespace DoFactory.GangOfFour.Command.RealWorld
 {
 
     /// <summary>
-    /// The 'Command' abstract class
+    /// The 'Command' Interface
     /// </summary>
-    abstract class Command
+    interface ICommand
     {
-        public abstract void Execute();
-        public abstract void UnExecute();
+        void Execute();
+        void UnExecute();
     }
 }

Command/User.cs

@@ -13,7 +13,7 @@ class User
     {
         // Initializers
         private Calculator _calculator = new Calculator();
-        private List<Command> _commands = new List<Command>();
+        private List<ICommand> _commands = new List<ICommand>();
         private int _current = 0;
 
         public void Redo(int levels)
@@ -24,7 +24,7 @@ public void Redo(int levels)
             {
                 if (_current < _commands.Count - 1)
                 {
-                    Command command = _commands[_current++];
+                    ICommand command = _commands[_current++];
                     command.Execute();
                 }
             }
@@ -38,7 +38,7 @@ public void Undo(int levels)
             {
                 if (_current > 0)
                 {
-                    Command command = _commands[--_current] as Command;
+                    ICommand command = _commands[--_current] as ICommand;
                     command.UnExecute();
                 }
             }
@@ -47,7 +47,7 @@ public void Undo(int levels)
         public void Compute(char @operator, int operand)
         {
             // Create command operation and execute it
-            Command command = new CalculatorCommand(
+            ICommand command = new CalculatorCommand(
               _calculator, @operator, operand);
             command.Execute();