重构指南 - 尽快返回（Return ASAP ）

尽快返回就是如果方法中的条件判断可以得到结果，则尽快返回该结果。

1. 检查条件，如果不满足就立即返回，不执行下面的逻辑。

2. 当包含大量的if else嵌套，代码可读性变差，也容易出现异常。

3. 在重构时， 尽量使简单判断优先执行，尽快返回，提高性能。

代码重构前

using System.Collections.Generic;
using System.Linq;
using LosTechies.DaysOfRefactoring.SampleCode.BreakMethod.After;
using Customer = LosTechies.DaysOfRefactoring.BreakResponsibilities.After.Customer;

namespace LosTechies.DaysOfRefactoring.SampleCode.ReturnASAP.Before
{
    public class Order
    {
        public Customer Customer { get; private set; }

        public decimal CalculateOrder(Customer customer, IEnumerable<Product> products, decimal discounts)
        {
            Customer = customer;
            decimal orderTotal = 0m;

            if (products.Count() > )
            {
                orderTotal = products.Sum(p => p.Price);
                if (discounts > )
                {
                    orderTotal -= discounts;
                }
            }

            return orderTotal;
        }
    }
}

代码重构后

using System.Collections.Generic;
using System.Linq;
using LosTechies.DaysOfRefactoring.SampleCode.BreakMethod.After;
using Customer = LosTechies.DaysOfRefactoring.BreakResponsibilities.After.Customer;

namespace LosTechies.DaysOfRefactoring.SampleCode.ReturnASAP.After
{
    public class Order
    {
        public Customer Customer { get; private set; }

        public decimal CalculateOrder(Customer customer, IEnumerable<Product> products, decimal discounts)
        {
            if (products.Count() == )
                return ;

            Customer = customer;
            decimal orderTotal = products.Sum(p => p.Price);

            if (discounts == )
                return orderTotal;

            orderTotal -= discounts;

            return orderTotal;
        }
    }
}

代码重构后， 可读性提高，逻辑清晰。