1 files changed, 51 insertions, 0 deletions
diff --git a/Xamarin.Forms.Core/Interactivity/Condition.cs b/Xamarin.Forms.Core/Interactivity/Condition.cs
new file mode 100644
index 00000000..aad921cf
--- /dev/null
+++ b/Xamarin.Forms.Core/Interactivity/Condition.cs
@@ -0,0 +1,51 @@
+using System;
+
+namespace Xamarin.Forms
+{
+	public abstract class Condition
+	{
+		Action<BindableObject, bool, bool> _conditionChanged;
+
+		bool _isSealed;
+
+		internal Condition()
+		{
+		}
+
+		internal Action<BindableObject, bool, bool> ConditionChanged
+		{
+			get { return _conditionChanged; }
+			set
+			{
+				if (_conditionChanged == value)
+					return;
+				if (_conditionChanged != null)
+					throw new InvalidOperationException("The same condition instance can not be reused");
+				_conditionChanged = value;
+			}
+		}
+
+		internal bool IsSealed
+		{
+			get { return _isSealed; }
+			set
+			{
+				if (_isSealed == value)
+					return;
+				if (!value)
+					throw new InvalidOperationException("What is sealed can not be unsealed.");
+				_isSealed = value;
+				OnSealed();
+			}
+		}
+
+		internal abstract bool GetState(BindableObject bindable);
+
+		internal virtual void OnSealed()
+		{
+		}
+
+		internal abstract void SetUp(BindableObject bindable);
+		internal abstract void TearDown(BindableObject bindable);
+	}
+}
+\ No newline at end of file