如何将正常的foreach循环转换为c＃中的lambda表达式？ [英] How to convert normal foreach loop into lambda expression in c# ?

问题描述

•public static Collection <   SalesPlan  >  GetCurrentPlan（PurchasePlanRequest purchasePlanRequest）
 {
 SalesCustomerManager salesCustomerManager = new SalesCustomerManager（）; 
 SalesCustomer salesCustomer = new SalesCustomer（）; 
 
 salesCustomer.ReportingCustomerNumber = purchasePlanRequest.ReportingCustomerId; 
集合<   SalesPlan  >  salesPlanCollection = new Collection <   SalesPlan  > < /跨度>（）; 
 salesCustomer = salesCustomerManager.GetCustomerLinesPlansCoverages（salesCustomer）; 
集合<   SalesPlan  >  renewalPlan = new Collection <   SalesPlan  > < /跨度>（）; 
集合<   SalesPlan  >  currentPlan = new Collection <   SalesPlan  > < /跨度>（）; 
  foreach（SalesLineOfBusiness lob in salesCustomer.SalesLineOfBusinessCollection）
 {
 if（lob.LineOfBusinessCode == purchasePlanRequest.LOBCode）
 {
 foreach（SalesPlan salepln in lob.SalesPlanCollection）
 {
 //比较PlanEffectiveDate等于CurrentRenewalDate。 
 if（purchasePlanRequest.PlanEffectiveDate == currentRenewalDate）
 {
 if（salepln.IsRenewalPlan == true）
 {
 currentPlan.Add（salepln）; 
} 
} 
其他
 {
 if（salepln.IsCurrentPlan == true）
 {
 currentPlan.Add（salepln）; 
} 
} 
} 
} 
}  return currentPlan; 
} 
在粗体代码foreach循环中，我想使用Lambda表达式而不是Foreach循环。 
任何人都可以建议我这样做...。

解决方案

你可以使用LINQ在集合上运行循环，如下所示 -

lob.SalesPlanCollection.ForEach（i => i.DoStuff（））;

我的第一个问题是为什么？你想把它转换成Lambda吗？因为我个人没有看到代码有什么问题



但要回答你的问题;

 lob.SalesPLanCollection.ForEach（i = >  
 {
  / /  比较PlanEffectiveDate等于CurrentRenewalDate。 
  if （purchasePlanRequest.PlanEffectiveDate = = currentRenewalDate）
 {
  if （salepln.IsRenewalPlan ==  true ）
 {
 currentPlan.Add（salepln）; 
} 
  else  
 {
  if （salepln.IsCurrentPlan ==  true ）
 {
 currentPlan.Add（salepln） ; 
} 
} 
} 
 
}）; 
 

您可以在表达式中添加Where子句，以限制迭代的数据量...

 public static Collection< salesplan> GetCurrentPlan（PurchasePlanRequest purchasePlanRequest）
 {
 SalesCustomerManager salesCustomerManager = new SalesCustomerManager（）; 
 SalesCustomer salesCustomer = new SalesCustomer（）; 
 
 salesCustomer.ReportingCustomerNumber = purchasePlanRequest.ReportingCustomerId; 
 Collection< salesplan> salesPlanCollection = new Collection< salesplan>（）; 
 salesCustomer = salesCustomerManager.GetCustomerLinesPlansCoverages（salesCustomer）; 
 Collection< salesplan> renewalPlan = new Collection< salesplan>（）; 
 Collection< salesplan> currentPlan = new Collection< salesplan>（）; 
 foreach（SalesLineOfBusiness lob in salesCustomer.SalesLineOfBusinessCollection.Where（o => o.LineOfBusinessCode == purchasePlanRequest.LOBCode））
 {
 
 lob.SalesPLanCollection.ForEach（i = > 
 {
 //比较PlanEffectiveDate等于CurrentRenewalDate。
 if（purchasePlanRequest.PlanEffectiveDate == currentRenewalDate）
 {
 if（salepln.IsRenewalPlan == true） ）
 {
 currentPlan.Add（salepln）; 
} 
 else 
 {
 if（salepln.IsCurrentPlan == true）
 { 
 currentPlan.Add（salepln）; 
} 
} 
} 
 
}）; 
 
} 
 
 return currentPlan; 
}< / salesplan>< / salesplan>< / salesplan>< / salesplan>< / salesplan>< / salesplan>< / salesplan> 

•   public static Collection<SalesPlan> GetCurrentPlan(PurchasePlanRequest purchasePlanRequest)
        {
            SalesCustomerManager salesCustomerManager = new SalesCustomerManager();
            SalesCustomer salesCustomer = new SalesCustomer();

            salesCustomer.ReportingCustomerNumber = purchasePlanRequest.ReportingCustomerId;
            Collection<SalesPlan> salesPlanCollection = new Collection<SalesPlan>();
            salesCustomer = salesCustomerManager.GetCustomerLinesPlansCoverages(salesCustomer);
            Collection<SalesPlan> renewalPlan = new Collection<SalesPlan>();
            Collection<SalesPlan> currentPlan = new Collection<SalesPlan>();
            foreach (SalesLineOfBusiness lob in salesCustomer.SalesLineOfBusinessCollection)
            {
                if (lob.LineOfBusinessCode == purchasePlanRequest.LOBCode)
                {
                    foreach (SalesPlan salepln in lob.SalesPlanCollection)
                    {
                        //Compare PlanEffectiveDate is equal to CurrentRenewalDate.
                        if (purchasePlanRequest.PlanEffectiveDate == currentRenewalDate)
                        {
                            if (salepln.IsRenewalPlan == true)
                            {
                                currentPlan.Add(salepln);
                            }
                        }
                        else
                        {
                            if (salepln.IsCurrentPlan == true)
                            {
                                currentPlan.Add(salepln);
                            }
                        }
                    }
                }
            }            return currentPlan;
        }
In the bold code foreach loop, I want to use Lambda expression instead of Foreach loop.
Can anybody suggest me approach of doing so….

解决方案

You can run a loop over a collection using LINQ as below -
lob.SalesPlanCollection.ForEach(i => i.DoStuff());

My first question would be WHY? would you want to convert it too Lambda? As I personally dont see anything wrong with the code

but to answer your question;

lob.SalesPLanCollection.ForEach(i =>
{
  //Compare PlanEffectiveDate is equal to CurrentRenewalDate.
  if (purchasePlanRequest.PlanEffectiveDate == currentRenewalDate)
  {
    if (salepln.IsRenewalPlan == true)
    {
      currentPlan.Add(salepln);
    }
    else
    {
      if (salepln.IsCurrentPlan == true)
      {
        currentPlan.Add(salepln);
      }
    }
  }

});

You can add a Where clause to your expression to limit the amount of data being iterated over as well...

public static Collection<salesplan> GetCurrentPlan(PurchasePlanRequest purchasePlanRequest)
        {
            SalesCustomerManager salesCustomerManager = new SalesCustomerManager();
            SalesCustomer salesCustomer = new SalesCustomer();
 
            salesCustomer.ReportingCustomerNumber = purchasePlanRequest.ReportingCustomerId;
            Collection<salesplan> salesPlanCollection = new Collection<salesplan>();
            salesCustomer = salesCustomerManager.GetCustomerLinesPlansCoverages(salesCustomer);
            Collection<salesplan> renewalPlan = new Collection<salesplan>();
            Collection<salesplan> currentPlan = new Collection<salesplan>();
            foreach (SalesLineOfBusiness lob in salesCustomer.SalesLineOfBusinessCollection.Where(o => o.LineOfBusinessCode == purchasePlanRequest.LOBCode))
            {
                
                lob.SalesPLanCollection.ForEach(i =>
                {
                  //Compare PlanEffectiveDate is equal to CurrentRenewalDate.
                  if (purchasePlanRequest.PlanEffectiveDate == currentRenewalDate)
                  {
                    if (salepln.IsRenewalPlan == true)
                    {
                      currentPlan.Add(salepln);
                    }
                    else
                    {
                      if (salepln.IsCurrentPlan == true)
                      {
                        currentPlan.Add(salepln);
                      }
                    }
                  }
                 
                });
                
            }            

            return currentPlan;
        }</salesplan></salesplan></salesplan></salesplan></salesplan></salesplan></salesplan>

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