Question

我有以下代码，我尝试重构此代码以删除重复的代码。然而，每当我尝试重构它时，我都会陷入困境。是否有人可以帮我解决这个问题。

    public static IOrderedQueryable<T> ObjectSort<T>(this IQueryable<T> entities, Expression<Func<T, object>> expression, string order = "asc")
    {
        var sortOrder = order == "asc" ? SortOrder.Ascending : SortOrder.Descending;
        return entities.ObjectSort(expression, sortOrder);
    }

    public static IOrderedQueryable<T> ObjectThenBy<T>(this IOrderedQueryable<T> entities, Expression<Func<T, object>> expression, string order = "asc")
    {
        var sortOrder = order == "asc" ? SortOrder.Ascending : SortOrder.Descending;
        return entities.ObjectThenBy(expression, sortOrder);
    }

    public static IOrderedQueryable<T> ObjectSort<T>(this IQueryable<T> entities, Expression<Func<T, object>> expression, SortOrder order = SortOrder.Ascending)
    {
        var unaryExpression = expression.Body as UnaryExpression;
        if (unaryExpression != null)
        {
            var propertyExpression = (MemberExpression)unaryExpression.Operand;
            var parameters = expression.Parameters;

            if (propertyExpression.Type == typeof(DateTime))
            {
                var newExpression = Expression.Lambda<Func<T, DateTime>>(propertyExpression, parameters);
                return order == SortOrder.Ascending ? entities.OrderBy(newExpression) : entities.OrderByDescending(newExpression);
            }

            if (propertyExpression.Type == typeof(DateTime?))
            {
                var newExpression = Expression.Lambda<Func<T, DateTime?>>(propertyExpression, parameters);
                return order == SortOrder.Ascending ? entities.OrderBy(newExpression) : entities.OrderByDescending(newExpression);
            }

            if (propertyExpression.Type == typeof(int))
            {
                var newExpression = Expression.Lambda<Func<T, int>>(propertyExpression, parameters);
                return order == SortOrder.Ascending ? entities.OrderBy(newExpression) : entities.OrderByDescending(newExpression);
            }

            if (propertyExpression.Type == typeof(int?))
            {
                var newExpression = Expression.Lambda<Func<T, int?>>(propertyExpression, parameters);
                return order == SortOrder.Ascending ? entities.OrderBy(newExpression) : entities.OrderByDescending(newExpression);
            }

            if (propertyExpression.Type == typeof(bool))
            {
                var newExpression = Expression.Lambda<Func<T, bool>>(propertyExpression, parameters);
                return order == SortOrder.Ascending ? entities.OrderBy(newExpression) : entities.OrderByDescending(newExpression);
            }

            throw new NotSupportedException("Object type resolution not implemented for this type");
        }
        return order == SortOrder.Ascending ? entities.OrderBy(expression) : entities.OrderByDescending(expression);
    }

    public static IOrderedQueryable<T> ObjectThenBy<T>(this IOrderedQueryable<T> entities, Expression<Func<T, object>> expression, SortOrder order = SortOrder.Ascending)
    {
        var unaryExpression = expression.Body as UnaryExpression;
        if (unaryExpression != null)
        {
            var propertyExpression = (MemberExpression)unaryExpression.Operand;
            var parameters = expression.Parameters;

            if (propertyExpression.Type == typeof(DateTime))
            {
                var newExpression = Expression.Lambda<Func<T, DateTime>>(propertyExpression, parameters);
                return order == SortOrder.Ascending ? entities.ThenBy(newExpression) : entities.ThenByDescending(newExpression);
            }

            if (propertyExpression.Type == typeof(DateTime?))
            {
                var newExpression = Expression.Lambda<Func<T, DateTime?>>(propertyExpression, parameters);
                return order == SortOrder.Ascending ? entities.ThenBy(newExpression) : entities.ThenByDescending(newExpression);
            }

            if (propertyExpression.Type == typeof(int))
            {
                var newExpression = Expression.Lambda<Func<T, int>>(propertyExpression, parameters);
                return order == SortOrder.Ascending ? entities.ThenBy(newExpression) : entities.ThenByDescending(newExpression);
            }

            if (propertyExpression.Type == typeof(int?))
            {
                var newExpression = Expression.Lambda<Func<T, int?>>(propertyExpression, parameters);
                return order == SortOrder.Ascending ? entities.ThenBy(newExpression) : entities.ThenByDescending(newExpression);
            }

            if (propertyExpression.Type == typeof(bool))
            {
                var newExpression = Expression.Lambda<Func<T, bool>>(propertyExpression, parameters);
                return order == SortOrder.Ascending ? entities.ThenBy(newExpression) : entities.ThenByDescending(newExpression);
            }

            throw new NotSupportedException("Object type resolution not implemented for this type");
        }
        return order == SortOrder.Ascending ? entities.ThenBy(expression) : entities.ThenByDescending(expression);
    }

请注意区别在于OrderBy和ThenBy ......其余的完全一样。希望有人知道重构这个的方法。我试图创建一个Func参数来传递OrderBy或ThenBy方法。然而，我尝试的一切都被卡住了。

Answer 1

OrderBy和ThenBy之间的区别在于OrderBy期望IQueryable，而ThenBy期望IOrderedqueryAble。

现在要使用OrderBy或ThenBy，您需要确定该集合是IQueryable还是IOrderedQueryAble。

之后，如果它是IQueryable，请调用OrderBy。如果它是IOrderedQueryable，则调用ThenBy（在转换为IOrderedQueryable之后。

重构的代码段变为

    public static IOrderedQueryable<T> ObjectSortRefactored<T>(this IQueryable<T> entities, Expression<Func<T, object>> expression, SortOrder order = SortOrder.Ascending)
    {
        var unaryExpression = expression.Body as UnaryExpression;
        if (unaryExpression != null)
        {
            var propertyExpression = (MemberExpression)unaryExpression.Operand;
            var parameters = expression.Parameters;

            if (propertyExpression.Type == typeof(DateTime))
            {
                var newExpression = Expression.Lambda<Func<T, DateTime>>(propertyExpression, parameters);
                return order == SortOrder.Ascending ? entities.OrderBy(newExpression) : entities.OrderByDescending(newExpression);
            }

            if (propertyExpression.Type == typeof(DateTime?))
            {
                var newExpression = Expression.Lambda<Func<T, DateTime?>>(propertyExpression, parameters);
                return order == SortOrder.Ascending ? entities.OrderBy(newExpression) : entities.OrderByDescending(newExpression);
            }

            if (propertyExpression.Type == typeof(int))
            {
                var newExpression = Expression.Lambda<Func<T, int>>(propertyExpression, parameters);
                return order == SortOrder.Ascending ? entities.OrderBy(newExpression) : entities.OrderByDescending(newExpression);
            }

            if (propertyExpression.Type == typeof(int?))
            {
                var newExpression = Expression.Lambda<Func<T, int?>>(propertyExpression, parameters);
                return order == SortOrder.Ascending ? entities.OrderBy(newExpression) : entities.OrderByDescending(newExpression);
            }

            if (propertyExpression.Type == typeof(bool))
            {
                var newExpression = Expression.Lambda<Func<T, bool>>(propertyExpression, parameters);
                return order == SortOrder.Ascending ? entities.OrderBy(newExpression) : entities.OrderByDescending(newExpression);
            }

            throw new NotSupportedException("Object type resolution not implemented for this type");
        }
        if(entities.GetType().IsAssignableFrom(typeof(IOrderedQueryable<T>)))
                return order == SortOrder.Ascending ? (entities as IOrderedQueryable<T>).ThenBy(expression) : (entities as IOrderedQueryable<T>).ThenByDescending(expression);

        return order == SortOrder.Ascending ? entities.OrderBy(expression) : entities.OrderByDescending(expression);
    }

我还没有测试过上面的代码片段。

重构linq表达式删除重复的代码

1 个答案: