OR together LINQ expressions for Where clauses etc

LINQOrExpressionCombiner.cs

class Or
{
    public static Expression<Func<T, bool>> Combine<T>(Expression<Func<T, bool>> left, Expression<Func<T, bool>> right)
    {
        var parameter = Expression.Parameter(typeof(T), "p");
        var combined = new ParameterReplacer(parameter).Visit(Expression.OrElse(left.Body, right.Body));
        return Expression.Lambda<Func<T, bool>>(combined, parameter);
    }

    class ParameterReplacer : ExpressionVisitor
    {
        readonly ParameterExpression parameter;

        internal ParameterReplacer(ParameterExpression parameter)
        {
            this.parameter = parameter;
        }

        protected override Expression VisitParameter(ParameterExpression node)
        {
            return parameter;
        }
    }
}