1 files changed, 250 insertions, 0 deletions
diff --git a/src/DotNetOpenAuth.Core/Requires.cs b/src/DotNetOpenAuth.Core/Requires.cs
new file mode 100644
index 0000000..4be6da0
--- /dev/null
+++ b/src/DotNetOpenAuth.Core/Requires.cs
@@ -0,0 +1,250 @@
+//-----------------------------------------------------------------------
+// <copyright file="Requires.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.Globalization;
+	using System.Linq;
+	using System.Text;
+	using DotNetOpenAuth.Messaging;
+
+	/// <summary>
+	/// Argument validation checks that throw some kind of ArgumentException when they fail (unless otherwise noted).
+	/// </summary>
+	internal static class Requires {
+		/// <summary>
+		/// Validates that a given parameter is not null.
+		/// </summary>
+		/// <typeparam name="T">The type of the parameter</typeparam>
+		/// <param name="value">The value.</param>
+		/// <param name="parameterName">Name of the parameter.</param>
+#if !CLR4
+		[ContractArgumentValidator]
+#endif
+		[Pure, DebuggerStepThrough]
+		internal static void NotNull<T>(T value, string parameterName) where T : class {
+			if (value == null) {
+				throw new ArgumentNullException(parameterName);
+			}
+
+			Contract.EndContractBlock();
+		}
+
+		/// <summary>
+		/// Validates that a parameter is not null or empty.
+		/// </summary>
+		/// <param name="value">The value.</param>
+		/// <param name="parameterName">Name of the parameter.</param>
+#if !CLR4
+		[ContractArgumentValidator]
+#endif
+		[Pure, DebuggerStepThrough]
+		internal static void NotNullOrEmpty(string value, string parameterName) {
+			NotNull(value, parameterName);
+			True(value.Length > 0, parameterName, Strings.EmptyStringNotAllowed);
+			Contract.EndContractBlock();
+		}
+
+		/// <summary>
+		/// Validates that an array is not null or empty.
+		/// </summary>
+		/// <typeparam name="T">The type of the elements in the sequence.</typeparam>
+		/// <param name="value">The value.</param>
+		/// <param name="parameterName">Name of the parameter.</param>
+#if !CLR4
+		[ContractArgumentValidator]
+#endif
+		[Pure, DebuggerStepThrough]
+		internal static void NotNullOrEmpty<T>(IEnumerable<T> value, string parameterName) {
+			NotNull(value, parameterName);
+			True(value.Any(), parameterName, Strings.InvalidArgument);
+			Contract.EndContractBlock();
+		}
+
+		/// <summary>
+		/// Validates that an argument is either null or is a sequence with no null elements.
+		/// </summary>
+		/// <typeparam name="T">The type of elements in the sequence.</typeparam>
+		/// <param name="sequence">The sequence.</param>
+		/// <param name="parameterName">Name of the parameter.</param>
+#if !CLR4
+		[ContractArgumentValidator]
+#endif
+		[Pure, DebuggerStepThrough]
+		internal static void NullOrWithNoNullElements<T>(IEnumerable<T> sequence, string parameterName) where T : class {
+			if (sequence != null) {
+				if (sequence.Any(e => e == null)) {
+					throw new ArgumentException(MessagingStrings.SequenceContainsNullElement, parameterName);
+				}
+			}
+		}
+
+		/// <summary>
+		/// Validates some expression describing the acceptable range for an argument evaluates to true.
+		/// </summary>
+		/// <param name="condition">The expression that must evaluate to true to avoid an <see cref="ArgumentOutOfRangeException"/>.</param>
+		/// <param name="parameterName">Name of the parameter.</param>
+		/// <param name="message">The message to include with the exception.</param>
+#if !CLR4
+		[ContractArgumentValidator]
+#endif
+		[Pure, DebuggerStepThrough]
+		internal static void InRange(bool condition, string parameterName, string message = null) {
+			if (!condition) {
+				throw new ArgumentOutOfRangeException(parameterName, message);
+			}
+
+			Contract.EndContractBlock();
+		}
+
+		/// <summary>
+		/// Validates some expression describing the acceptable condition for an argument evaluates to true.
+		/// </summary>
+		/// <param name="condition">The expression that must evaluate to true to avoid an <see cref="ArgumentException"/>.</param>
+		/// <param name="parameterName">Name of the parameter.</param>
+		/// <param name="message">The message to include with the exception.</param>
+#if !CLR4
+		[ContractArgumentValidator]
+#endif
+		[Pure, DebuggerStepThrough]
+		internal static void True(bool condition, string parameterName = null, string message = null) {
+			if (!condition) {
+				throw new ArgumentException(message ?? Strings.InvalidArgument, parameterName);
+			}
+
+			Contract.EndContractBlock();
+		}
+
+		/// <summary>
+		/// Validates some expression describing the acceptable condition for an argument evaluates to true.
+		/// </summary>
+		/// <param name="condition">The expression that must evaluate to true to avoid an <see cref="ArgumentException"/>.</param>
+		/// <param name="parameterName">Name of the parameter.</param>
+		/// <param name="unformattedMessage">The unformatted message.</param>
+		/// <param name="args">Formatting arguments.</param>
+#if !CLR4
+		[ContractArgumentValidator]
+#endif
+		[Pure, DebuggerStepThrough]
+		internal static void True(bool condition, string parameterName, string unformattedMessage, params object[] args) {
+			if (!condition) {
+				throw new ArgumentException(String.Format(unformattedMessage, args), parameterName);
+			}
+
+			Contract.EndContractBlock();
+		}
+
+		/// <summary>
+		/// Validates some expression describing the acceptable condition for an argument evaluates to true.
+		/// </summary>
+		/// <param name="condition">The expression that must evaluate to true to avoid an <see cref="InvalidOperationException"/>.</param>
+#if !CLR4
+		[ContractArgumentValidator]
+#endif
+		[Pure, DebuggerStepThrough]
+		internal static void ValidState(bool condition) {
+			if (!condition) {
+				throw new InvalidOperationException();
+			}
+
+			Contract.EndContractBlock();
+		}
+
+		/// <summary>
+		/// Validates some expression describing the acceptable condition for an argument evaluates to true.
+		/// </summary>
+		/// <param name="condition">The expression that must evaluate to true to avoid an <see cref="InvalidOperationException"/>.</param>
+		/// <param name="message">The message to include with the exception.</param>
+#if !CLR4
+		[ContractArgumentValidator]
+#endif
+		[Pure, DebuggerStepThrough]
+		internal static void ValidState(bool condition, string message) {
+			if (!condition) {
+				throw new InvalidOperationException(message);
+			}
+
+			Contract.EndContractBlock();
+		}
+
+		/// <summary>
+		/// Validates some expression describing the acceptable condition for an argument evaluates to true.
+		/// </summary>
+		/// <param name="condition">The expression that must evaluate to true to avoid an <see cref="InvalidOperationException"/>.</param>
+		/// <param name="unformattedMessage">The unformatted message.</param>
+		/// <param name="args">Formatting arguments.</param>
+#if !CLR4
+		[ContractArgumentValidator]
+#endif
+		[Pure, DebuggerStepThrough]
+		internal static void ValidState(bool condition, string unformattedMessage, params object[] args) {
+			if (!condition) {
+				throw new InvalidOperationException(String.Format(CultureInfo.CurrentCulture, unformattedMessage, args));
+			}
+
+			Contract.EndContractBlock();
+		}
+
+		/// <summary>
+		/// Validates that some argument describes a type that is or derives from a required type.
+		/// </summary>
+		/// <typeparam name="T">The type that the argument must be or derive from.</typeparam>
+		/// <param name="type">The type given in the argument.</param>
+		/// <param name="parameterName">Name of the parameter.</param>
+#if !CLR4
+		[ContractArgumentValidator]
+#endif
+		[Pure, DebuggerStepThrough]
+		internal static void NotNullSubtype<T>(Type type, string parameterName) {
+			NotNull(type, parameterName);
+			True(typeof(T).IsAssignableFrom(type), parameterName, MessagingStrings.UnexpectedType, typeof(T).FullName, type.FullName);
+
+			Contract.EndContractBlock();
+		}
+
+		/// <summary>
+		/// Validates some expression describing the acceptable condition for an argument evaluates to true.
+		/// </summary>
+		/// <param name="condition">The expression that must evaluate to true to avoid an <see cref="FormatException"/>.</param>
+		/// <param name="message">The message.</param>
+#if !CLR4
+		[ContractArgumentValidator]
+#endif
+		[Pure, DebuggerStepThrough]
+		internal static void Format(bool condition, string message) {
+			if (!condition) {
+				throw new FormatException(message);
+			}
+
+			Contract.EndContractBlock();
+		}
+
+		/// <summary>
+		/// Throws an <see cref="NotSupportedException"/> if a condition does not evaluate to <c>true</c>.
+		/// </summary>
+		/// <param name="condition">The expression that must evaluate to true to avoid an <see cref="NotSupportedException"/>.</param>
+		/// <param name="message">The message.</param>
+		[Pure, DebuggerStepThrough]
+		internal static void Support(bool condition, string message) {
+			if (!condition) {
+				throw new NotSupportedException(message);
+			}
+		}
+
+		/// <summary>
+		/// Throws an <see cref="ArgumentException"/>
+		/// </summary>
+		/// <param name="parameterName">Name of the parameter.</param>
+		/// <param name="message">The message.</param>
+		[Pure, DebuggerStepThrough]
+		internal static void Fail(string parameterName, string message) {
+			throw new ArgumentException(message, parameterName);
+		}
+	}
+}