add

app2/Program.cs

@@ -0,0 +1,20 @@
+internal class Program
+{
+    private static void Main(string[] args)
+    {
+        Console.Write("light: ");
+        var light = Console.ReadLine();
+
+        if (light is not null) {
+            if (light.ToLower().Equals("red")) {
+                Console.WriteLine("stop");
+            } else if (light.ToLower().Equals("yellow")) {
+                Console.WriteLine("slow");
+            } else if (light.ToLower().Equals("green")) {
+                Console.WriteLine("go");
+            } else {
+                Console.WriteLine($"I don't know the color {light}");
+            }
+        }
+    }
+}

app2/app2.csproj

@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net7.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

app3/Program.cs

@@ -0,0 +1,23 @@
+internal class Program
+{
+    private static void Main(string[] args)
+    {
+        Console.Write("height: ");
+        var height = Console.ReadLine();
+
+        Console.Write("width: ");
+        var width = Console.ReadLine();
+
+        if (height is not null && width is not null) {
+            try {
+                int h = Int32.Parse(height);
+                int w = Int32.Parse(width);
+                int a = h * w;
+
+                Console.WriteLine($"h={h}, w={w}, a={a}");
+            } catch (Exception e) {
+                Console.WriteLine(e);
+            }
+        }
+    }
+}

app3/app3.csproj

@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net7.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

app4/Program.cs

@@ -0,0 +1,36 @@
+internal class Program
+{
+    private static void Main(string[] args)
+    {
+        while (true)
+        {
+            Console.Write("height: ");
+            var height = Console.ReadLine();
+
+            Console.Write("width: ");
+            var width = Console.ReadLine();
+
+            if (height is not null && width is not null)
+            {
+                if (height.ToLower().Equals("q") || width.ToLower().Equals("q")) {
+                    break;
+                }
+
+                try
+                {
+                    int h = Int32.Parse(height);
+                    int w = Int32.Parse(width);
+                    int a = h * w;
+
+                    Console.WriteLine($"h={h}, w={w}, a={a}");
+                }
+                catch (Exception e)
+                {
+                    Console.WriteLine(e);
+                }
+            }
+        }
+
+        Console.WriteLine("bye, see you later");
+    }
+}

app4/app4.csproj

@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net7.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

app5/Program.cs

@@ -0,0 +1,29 @@
+internal class Program
+{
+    private static void Main(string[] args)
+    {
+        Random random = new Random();
+
+        while (true) {
+            Console.Write("guess: ");
+            var guess = Console.ReadLine();
+
+            if (guess is not null) {
+                if (guess.ToLower().Equals("q")) {
+                    break;
+                }
+
+                var num = random.Next(0, 2);
+                var g = Int32.Parse(guess);
+
+                if (num == g) {
+                    Console.WriteLine("correct!");
+                } else {
+                    Console.WriteLine($"incorrect! guess={guess}, number={num}");
+                }
+            }
+        }
+
+        Console.WriteLine("bye, please play again!");
+    }
+}

app5/app5.csproj

@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net7.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>