AbstractCriterion.cs

using System;
using NHibernate.Engine;
using NHibernate.SqlCommand;

namespace NHibernate.Criterion
{
	/// <summary>
	/// Base class for <see cref="ICriterion"/> implementations.
	/// </summary>
	[Serializable]
	public abstract class AbstractCriterion : ICriterion
	{
		/// <summary>
		/// Gets a string representation of the <see cref="AbstractCriterion"/>.  
		/// </summary>
		/// <returns>
		/// A String that shows the contents of the <see cref="AbstractCriterion"/>.
		/// </returns>
		/// <remarks>
		/// This is not a well formed Sql fragment.  It is useful for logging what the <see cref="AbstractCriterion"/>
		/// looks like.
		/// </remarks>
		public abstract override string ToString();

		#region ICriterion Members

		/// <summary>
		/// Render a SqlString for the expression.
		/// </summary>
		/// <returns>A SqlString that contains a valid Sql fragment.</returns>
		public abstract SqlString ToSqlString(ICriteria criteria, ICriteriaQuery criteriaQuery);

		/// <summary>
		/// Return typed values for all parameters in the rendered SQL fragment
		/// </summary>
		/// <returns>An array of TypedValues for the Expression.</returns>
		public abstract TypedValue[] GetTypedValues(ICriteria criteria, ICriteriaQuery criteriaQuery);

		/// <summary>
		/// Return all projections used in this criterion
		/// </summary>
		/// <returns>An array of IProjection used by the Expression.</returns>
		public abstract IProjection[] GetProjections();

		#endregion

		#region Operator Overloading

		public static AbstractCriterion operator &(AbstractCriterion lhs, AbstractCriterion rhs)
		{
			return new AndExpression(lhs, rhs);
		}

		public static AbstractCriterion operator |(AbstractCriterion lhs, AbstractCriterion rhs)
		{
			return new OrExpression(lhs, rhs);
		}

		public static AbstractCriterion operator &(AbstractCriterion lhs, AbstractEmptinessExpression rhs)
		{
			return new AndExpression(lhs, rhs);
		}

		public static AbstractCriterion operator |(AbstractCriterion lhs, AbstractEmptinessExpression rhs)
		{
			return new OrExpression(lhs, rhs);
		}

		public static AbstractCriterion operator !(AbstractCriterion crit)
		{
			return new NotExpression(crit);
		}

		/// <summary>
		/// See here for details:
		/// http://steve.emxsoftware.com/NET/Overloading+the++and++operators
		/// </summary>
		public static bool operator false(AbstractCriterion criteria)
		{
			return false;
		}

		/// <summary>
		/// See here for details:
		/// http://steve.emxsoftware.com/NET/Overloading+the++and++operators
		/// </summary>
		public static bool operator true(AbstractCriterion criteria)
		{
			return false;
		}

		#endregion
	}
}