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copied!<p>To take the example literally, you could perform the combination in the question by building an <code>Expression</code> on the fly:</p> <pre><code> static IQueryable<T> WhereXElseY<T>( this IQueryable<T> query, Expression<Func<T, bool>> predicateA, Expression<Func<T, bool>> predicateB) { var condA = predicateA.Body; var param = predicateA.Parameters[0]; var body = Expression.OrElse( condA, Expression.AndAlso( Expression.Not(condA), Expression.Invoke( predicateB, param))); var lambda = Expression.Lambda<Func<T, bool>>( body, param); return query.Where(lambda); } </code></pre> <p>However, while this may work with LINQ-to-SQL, it won't work with EF since EF sadly hates <code>Expression.Invoke</code>. But as Jon notes; if you are sending this down to a database backend, the priority is irrelevant and you might as well go with the logically equivalent <code>condition1 || condition2</code>. You can combine expressions something like:</p> <pre><code> static IQueryable<T> WhereAny<T>( this IQueryable<T> query, params Expression<Func<T, bool>>[] predicates) { if (predicates == null) throw new ArgumentNullException("predicates"); if (predicates.Length == 0) return query.Where(x => false); if (predicates.Length == 1) return query.Where(predicates[0]); var param = predicates[0].Parameters[0]; var body = predicates[0].Body; for (int i = 1; i < predicates.Length; i++) { body = Expression.OrElse( body, Expression.Invoke(predicates[i], param)); } var lambda = Expression.Lambda<Func<T, bool>>(body, param); return query.Where(lambda); } </code></pre> <p>If I've missed the point, please clarify...</p>

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