1 files changed, 97 insertions, 0 deletions
diff --git a/src/DotNetOpenAuth.Core/Assumes.cs b/src/DotNetOpenAuth.Core/Assumes.cs
new file mode 100644
index 0000000..67205a2
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+++ b/src/DotNetOpenAuth.Core/Assumes.cs
@@ -0,0 +1,97 @@
+//-----------------------------------------------------------------------
+// <copyright file="Assumes.cs" company="Andrew Arnott">
+//     Copyright (c) Andrew Arnott. All rights reserved.
+// </copyright>
+//-----------------------------------------------------------------------
+
+namespace DotNetOpenAuth {
+	using System;
+	using System.Collections.Generic;
+	using System.Diagnostics;
+	using System.Diagnostics.Contracts;
+	using System.Linq;
+	using System.Text;
+
+	/// <summary>
+	/// Internal state consistency checks that throw an internal error exception when they fail.
+	/// </summary>
+	internal static class Assumes {
+		/// <summary>
+		/// Validates some expression describing the acceptable condition evaluates to true.
+		/// </summary>
+		/// <param name="condition">The expression that must evaluate to true to avoid an internal error exception.</param>
+		/// <param name="message">The message to include with the exception.</param>
+		[Pure, DebuggerStepThrough]
+		internal static void True(bool condition, string message = null) {
+			if (!condition) {
+				Fail(message);
+			}
+		}
+
+		/// <summary>
+		/// Validates some expression describing the acceptable condition evaluates to true.
+		/// </summary>
+		/// <param name="condition">The expression that must evaluate to true to avoid an internal error exception.</param>
+		/// <param name="unformattedMessage">The unformatted message.</param>
+		/// <param name="args">Formatting arguments.</param>
+		[Pure, DebuggerStepThrough]
+		internal static void True(bool condition, string unformattedMessage, params object[] args) {
+			if (!condition) {
+				Fail(String.Format(unformattedMessage, args));
+			}
+		}
+
+		/// <summary>
+		/// Throws an internal error exception.
+		/// </summary>
+		/// <param name="message">The message.</param>
+		[Pure, DebuggerStepThrough]
+		internal static void Fail(string message = null) {
+			if (message != null) {
+				throw new InternalErrorException(message);
+			} else {
+				throw new InternalErrorException();
+			}
+		}
+
+		/// <summary>
+		/// An internal error exception that should never be caught.
+		/// </summary>
+		[Serializable]
+		private class InternalErrorException : Exception {
+			/// <summary>
+			/// Initializes a new instance of the <see cref="InternalErrorException"/> class.
+			/// </summary>
+			internal InternalErrorException() {
+			}
+
+			/// <summary>
+			/// Initializes a new instance of the <see cref="InternalErrorException"/> class.
+			/// </summary>
+			/// <param name="message">The message.</param>
+			internal InternalErrorException(string message) : base(message) {
+			}
+
+			/// <summary>
+			/// Initializes a new instance of the <see cref="InternalErrorException"/> class.
+			/// </summary>
+			/// <param name="message">The message.</param>
+			/// <param name="inner">The inner exception.</param>
+			internal InternalErrorException(string message, Exception inner) : base(message, inner) {
+			}
+
+			/// <summary>
+			/// Initializes a new instance of the <see cref="InternalErrorException"/> class.
+			/// </summary>
+			/// <param name="info">The <see cref="T:System.Runtime.Serialization.SerializationInfo"/> that holds the serialized object data about the exception being thrown.</param>
+			/// <param name="context">The <see cref="T:System.Runtime.Serialization.StreamingContext"/> that contains contextual information about the source or destination.</param>
+			/// <exception cref="T:System.ArgumentNullException">The <paramref name="info"/> parameter is null. </exception>
+			/// <exception cref="T:System.Runtime.Serialization.SerializationException">The class name is null or <see cref="P:System.Exception.HResult"/> is zero (0). </exception>
+			protected InternalErrorException(
+			  System.Runtime.Serialization.SerializationInfo info,
+			  System.Runtime.Serialization.StreamingContext context)
+				: base(info, context) {
+			}
+		}
+	}
+}