1 files changed, 22 insertions, 0 deletions
diff --git a/src/DotNetOpenAuth.Core/PureAttribute.cs b/src/DotNetOpenAuth.Core/PureAttribute.cs
new file mode 100644
index 0000000..04f7ead
--- /dev/null
+++ b/src/DotNetOpenAuth.Core/PureAttribute.cs
@@ -0,0 +1,22 @@
+//-----------------------------------------------------------------------
+// <copyright file="PureAttribute.cs" company="Andrew Arnott">
+//     Copyright (c) Andrew Arnott. All rights reserved.
+// </copyright>
+//-----------------------------------------------------------------------
+
+namespace System.Diagnostics.Contracts {
+	using System;
+	using System.Collections.Generic;
+	using System.Linq;
+	using System.Text;
+
+#if !CLR4
+	/// <summary>
+	/// Designates a type or member as one that does not mutate any objects that were allocated
+	/// before the invocation of the member.
+	/// </summary>
+	[AttributeUsage(AttributeTargets.All, Inherited = false, AllowMultiple = false)]
+	internal sealed class PureAttribute : Attribute {
+	}
+#endif
+}