chore: net60/ZString related housekeeping (#385)

* Directory.Build.props: Remove duplicate entries from Demo and Performance projects
* Enable NRT for Demo and Performance projects
* Remove folder SmartFormat.ZString from former projects SmartFormat.ZString
* Remove obsolete entries from SmartFormat.sln
* Remove reference to former SmartFormat.ZString.dll from SmartFormat.csproj

src/Demo/Demo.csproj

@@ -5,9 +5,7 @@
     <TargetFrameworks>net6.0-windows</TargetFrameworks>
     <UseWindowsForms>true</UseWindowsForms>
     <ApplicationIcon>SmartFormat.Demo.ico</ApplicationIcon>
-    <LangVersion>8.0</LangVersion>
-    <Nullable>disable</Nullable>
-    <NoWarn>1591,1573</NoWarn>
+    <NoWarn>$(NoWarn);1591,1573</NoWarn>
   </PropertyGroup>
 
   <ItemGroup>

src/Demo/Program.cs

@@ -1,19 +1,18 @@
 using System;
 using System.Windows.Forms;
 
-namespace SmartFormat.Demo
+namespace SmartFormat.Demo;
+
+internal static class Program
 {
-    static class Program
+    /// <summary>
+    /// The main entry point for the application.
+    /// </summary>
+    [STAThread]
+    public static void Main()
     {
-        /// <summary>
-        /// The main entry point for the application.
-        /// </summary>
-        [STAThread]
-        static void Main()
-        {
-            Application.EnableVisualStyles();
-            Application.SetCompatibleTextRenderingDefault(false);
-            Application.Run(new SmartFormatDemo());
-        }
+        Application.EnableVisualStyles();
+        Application.SetCompatibleTextRenderingDefault(false);
+        Application.Run(new SmartFormatDemo());
     }
 }

src/Demo/Sample Extensions/ArgumentValidator.cs

@@ -1,27 +1,27 @@
-using System;
+#nullable enable
+using System;
 using System.Collections;
-#nullable enable
-namespace SmartFormat.Demo.Sample_Extensions
+
+namespace Demo.Sample_Extensions;
+
+public class ArgumentValidator
 {
-    public class ArgumentValidator
+    public static void CheckForNullReference(object? argument, string argumentName)
     {
-        public static void CheckForNullReference(object? argument, string argumentName)
-        {
-            if (argument != null) return;
-            throw new ArgumentNullException(argumentName);
-        }
+        if (argument != null) return;
+        throw new ArgumentNullException(argumentName);
+    }
 
-        public static void CheckForZeroValue(int argument, string argumentName)
-        {
-            if (argument != 0) return;
-            throw new ArgumentOutOfRangeException(argumentName, argument, argumentName + " cannot be zero");
-        }
+    public static void CheckForZeroValue(int argument, string argumentName)
+    {
+        if (argument != 0) return;
+        throw new ArgumentOutOfRangeException(argumentName, argument, argumentName + " cannot be zero");
+    }
 
-        public static void CheckForEmpty(IEnumerable argument, string argumentName)
-        {
-            var enumerator = argument.GetEnumerator();
-            if (enumerator.MoveNext()) return;
-            throw new ArgumentException(argumentName + " cannot be empty", argumentName);
-        }
+    public static void CheckForEmpty(IEnumerable argument, string argumentName)
+    {
+        var enumerator = argument.GetEnumerator();
+        if (enumerator.MoveNext()) return;
+        throw new ArgumentException(argumentName + " cannot be empty", argumentName);
     }
 }