如何避免两次使用lambda表达式 [英] How to avoid using lambda expressions twice

问题描述

在下面的代码中，我必须调用两次相同的表达式以获得与STRING匹配的First Item。有没有更好的方法呢？

Hi, In code below I have to call same expression twice to get First Item that matches STRING. Is there any better way of doing this?

if (InvoiceDetails.Where(x => x.IMEINumber == boostReconcile.BoostSheetLine.BoostImei).Count() > 0)
                   {
                       boostReconcile.InvoiceDetail = InvoiceDetails.Where(x => x.IMEINumber == boostReconcile.BoostSheetLine.BoostImei).First();
                   }

我尝试过：



没有任何关于代码的描述。

What I have tried:

There is nothing to describe about the code.

推荐答案

如果可以设置 boostReconcile.InvoiceDetail 到默认值（ null ，如果它是引用类型），当没有带有匹配IMEINumber的InvoiceDetail时，你可以这样做：

If it's ok to set boostReconcile.InvoiceDetail to its default value (null if it's a reference type) when there is no InvoiceDetail with a matching IMEINumber then you can do this instead:

boostReconcile.InvoiceDetail = InvoiceDetails.FirstOrDefault(x => x.IMEINumber == boostReconcile.BoostSheetLine.BoostImei);

如果只有0或1个InvoiceDetail符合此标准，则应使用SingleOrDefault（）代替：

If there should ever be only 0 or 1 InvoiceDetail that matches this criterion, you should use SingleOrDefault() instead:

boostReconcile.InvoiceDetail = InvoiceDetails.SingleOrDefault(x => x.IMEINumber == boostReconcile.BoostSheetLine.BoostImei);

尝试：

Try:

boostReconcile.InvoiceDetail = InvoiceDetails.FirstOrDefault(x => x.IMEINumber == boostReconcile.BoostSheetLine.BoostImei);

Enumerable.FirstOrDefault （TSource）方法（IEnumerable（TSource），Func（TSource，Boolean））（System.Linq） [ ^ ]



注意：如果没有匹配的记录，那将用 null 覆盖该属性。如果您已在该属性中有值，并且您不想覆盖它，请尝试：

Enumerable.FirstOrDefault(TSource) Method (IEnumerable(TSource), Func(TSource, Boolean)) (System.Linq)[^]

NB: That will overwrite the property with null if there are no matching records. If you already have a value in the property, and you don't want to overwrite it, then try:

boostReconcile.InvoiceDetail = InvoiceDetails.FirstOrDefault(x => x.IMEINumber == boostReconcile.BoostSheetLine.BoostImei) ?? boostReconcile.InvoiceDetail;

尝试

var g = InvoiceDetails.Where(x => x.IMEINumber == boostReconcile.BoostSheetLine.BoostImei);
if (g.Count() > 0)
                   {
                       boostReconcile.InvoiceDetail = g.First();
                   }

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