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MyCode.Project.Infrastructure/Specifications/Specification.cs

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+
+using System;
+using System.Linq.Expressions;
+
+namespace MyCode.Project.Infrastructure
+{
+    /// <summary>
+    /// Represents the base class for specifications.
+    /// </summary>
+    /// <typeparam name="T">The type of the object to which the specification is applied.</typeparam>
+    public abstract class Specification<T> : ISpecification<T>
+    {
+        #region Public Methods
+        /// <summary>
+        /// Evaluates a LINQ expression to its corresponding specification.
+        /// </summary>
+        /// <param name="expression">The LINQ expression to be evaluated.</param>
+        /// <returns>The specification which represents the same semantics as the given LINQ expression.</returns>
+        public static Specification<T> Eval(Expression<Func<T, bool>> expression)
+        {
+            return new ExpressionSpecification<T>(expression);
+        }
+        #endregion
+
+        #region ISpecification<T> Members
+        /// <summary>
+        /// Returns a <see cref="System.Boolean"/> value which indicates whether the specification
+        /// is satisfied by the given object.
+        /// </summary>
+        /// <param name="obj">The object to which the specification is applied.</param>
+        /// <returns>True if the specification is satisfied, otherwise false.</returns>
+        public virtual bool IsSatisfiedBy(T obj)
+        {
+            return this.GetExpression().Compile()(obj);
+        }
+        /// <summary>
+        /// Combines the current specification instance with another specification instance
+        /// and returns the combined specification which represents that both the current and
+        /// the given specification must be satisfied by the given object.
+        /// </summary>
+        /// <param name="other">The specification instance with which the current specification
+        /// is combined.</param>
+        /// <returns>The combined specification instance.</returns>
+        public ISpecification<T> And(ISpecification<T> other)
+        {
+            return new AndSpecification<T>(this, other);
+        }
+        /// <summary>
+        /// Combines the current specification instance with another specification instance
+        /// and returns the combined specification which represents that either the current or
+        /// the given specification should be satisfied by the given object.
+        /// </summary>
+        /// <param name="other">The specification instance with which the current specification
+        /// is combined.</param>
+        /// <returns>The combined specification instance.</returns>
+        public ISpecification<T> Or(ISpecification<T> other)
+        {
+            return new OrSpecification<T>(this, other);
+        }
+        /// <summary>
+        /// Combines the current specification instance with another specification instance
+        /// and returns the combined specification which represents that the current specification
+        /// should be satisfied by the given object but the specified specification should not.
+        /// </summary>
+        /// <param name="other">The specification instance with which the current specification
+        /// is combined.</param>
+        /// <returns>The combined specification instance.</returns>
+        public ISpecification<T> AndNot(ISpecification<T> other)
+        {
+            return new AndNotSpecification<T>(this, other);
+        }
+        /// <summary>
+        /// Reverses the current specification instance and returns a specification which represents
+        /// the semantics opposite to the current specification.
+        /// </summary>
+        /// <returns>The reversed specification instance.</returns>
+        public ISpecification<T> Not()
+        {
+            return new NotSpecification<T>(this);
+        }
+        /// <summary>
+        /// Gets the LINQ expression which represents the current specification.
+        /// </summary>
+        /// <returns>The LINQ expression.</returns>
+        public abstract Expression<Func<T, bool>> GetExpression();
+        #endregion
+    }
+}