support for .NET framework 3.5

Still have bugs

Net35/HandyControl_Net35/Data/SystemVersionInfo.cs

@@ -0,0 +1,76 @@
+// reference from https://github.com/sourcechord/FluentWPF/blob/master/FluentWPF/Utility/VersionInfo.cs
+// LICENSE: https://github.com/sourcechord/FluentWPF/blob/master/LICENSE
+
+using System;
+
+namespace HandyControl.Data
+{
+    public struct SystemVersionInfo
+    {
+        public static SystemVersionInfo Windows10 => new SystemVersionInfo(10, 0, 10240);
+        public static SystemVersionInfo Windows10_1809 => new SystemVersionInfo(10, 0, 17763);
+
+        public SystemVersionInfo(int major, int minor, int build)
+        {
+            Major = major;
+            Minor = minor;
+            Build = build;
+        }
+
+        public int Major { get; }
+
+        public int Minor { get; }
+
+        public int Build { get; }
+
+        public bool Equals(SystemVersionInfo other) => Major == other.Major && Minor == other.Minor && Build == other.Build;
+
+        public override bool Equals(object obj) => obj is SystemVersionInfo other && Equals(other);
+
+        public override int GetHashCode() => Major.GetHashCode() ^ Minor.GetHashCode() ^ Build.GetHashCode();
+
+        public static bool operator ==(SystemVersionInfo left, SystemVersionInfo right) => left.Equals(right);
+
+        public static bool operator !=(SystemVersionInfo left, SystemVersionInfo right) => !(left == right);
+        
+        public int CompareTo(SystemVersionInfo other)
+        {
+            if (Major != other.Major)
+            {
+                return Major.CompareTo(other.Major);
+            }
+
+            if (Minor != other.Minor)
+            {
+                return Minor.CompareTo(other.Minor);
+            }
+
+            if (Build != other.Build)
+            {
+                return Build.CompareTo(other.Build);
+            }
+
+            return 0;
+        }
+
+        public int CompareTo(object obj)
+        {
+            if (!(obj is SystemVersionInfo other))
+            {
+                throw new ArgumentException();
+            }
+
+            return CompareTo(other);
+        }
+
+        public static bool operator <(SystemVersionInfo left, SystemVersionInfo right) => left.CompareTo(right) < 0;
+
+        public static bool operator <=(SystemVersionInfo left, SystemVersionInfo right) => left.CompareTo(right) <= 0;
+
+        public static bool operator >(SystemVersionInfo left, SystemVersionInfo right) => left.CompareTo(right) > 0;
+
+        public static bool operator >=(SystemVersionInfo left, SystemVersionInfo right) => left.CompareTo(right) >= 0;
+
+        public override string ToString() => $"{Major}.{Minor}.{Build}";
+    }
+}