support for .NET framework 3.5

Still have bugs

Net35/HandyControl_Net35/Interactivity/DefaultTriggerAttribute.cs

@@ -0,0 +1,49 @@
+using System;
+using System.Collections;
+using System.Globalization;
+
+namespace HandyControl.Interactivity
+{
+    [AttributeUsage(AttributeTargets.Property | AttributeTargets.Class, AllowMultiple = true)]
+    public sealed class DefaultTriggerAttribute : Attribute
+    {
+        private readonly object[] _parameters;
+
+        public DefaultTriggerAttribute(Type targetType, Type triggerType, object parameter) : this(targetType,
+            triggerType, new[] {parameter})
+        {
+        }
+
+        public DefaultTriggerAttribute(Type targetType, Type triggerType, params object[] parameters)
+        {
+            if (!typeof(TriggerBase).IsAssignableFrom(triggerType))
+                throw new ArgumentException(string.Format(CultureInfo.CurrentCulture,
+                    ExceptionStringTable.DefaultTriggerAttributeInvalidTriggerTypeSpecifiedExceptionMessage,
+                    new object[] {triggerType.Name}));
+            TargetType = targetType;
+            TriggerType = triggerType;
+            _parameters = parameters;
+        }
+
+        public IEnumerable Parameters =>
+            _parameters;
+
+        public Type TargetType { get; }
+
+        public Type TriggerType { get; }
+
+        public TriggerBase Instantiate()
+        {
+            object obj2 = null;
+            try
+            {
+                obj2 = Activator.CreateInstance(TriggerType, _parameters);
+            }
+            catch
+            {
+                // ignored
+            }
+            return (TriggerBase) obj2;
+        }
+    }
+}