Question

我问自己如何简化这样的事情

var myList = new List<MyObject>
pulic MyObject FindBestMatching(int Prop1Value, int Prop2Value, int Prop3Value)
{
    MyObject item = null;
    item = myList.Find(x => x.Prop1 == Prop1Value && x.Prop2 == Prop2Value && x.Prop3 == Prop3Value);
    if(item != null)
    {
         return item;
    }
    item = myList.Find(x => x.Prop1 == Prop1Value && x.Prop2 == Prop2Value);
    if(item != null)
    {
         return item;
    }
    item = myList.Find(x => x.Prop1 == Prop1Value);
    // Doesn't matter if its null
    return item;
}

我确信LINQ提供了一个解决方案，但我无法找到它：）

谢谢。

Answer 1

从技术上讲，您可以将当前代码简化为

  pulic MyObject FindBestMatching(int Prop1Value, int Prop2Value, int Prop3Value) {
    return 
         myList.Find(x => x.Prop1 == Prop1Value && x.Prop2 == Prop2Value && x.Prop3 == Prop3Value)
      ?? myList.Find(x => x.Prop1 == Prop1Value && x.Prop2 == Prop2Value)
      ?? myList.Find(x => x.Prop1 == Prop1Value);    
  }

但是Find（扫描整个列表）可能是一项代价高昂的操作，如果是这种情况，您只能在一个循环中找到最佳匹配：

  public MyObject FindBestMatching(int Prop1Value, int Prop2Value, int Prop3Value) {
    MyObject result1 = null;
    MyObject result2 = null;

    foreach (MyObject item in myList) {
      if (item.Prop1 == Prop1Value) {
        result1 = item;

        if (item.Prop2 == Prop2Value) {
          result2 = item;

          if (item.Prop3 == Prop3Value) 
            return item; 
        }
      }  
    }

    return result2 ?? result1; 
  }

Answer 2

试试这个：

public MyObject FindBestMatching(int Prop1Value, int Prop2Value, int Prop3Value)
{
    return myList.FirstOrDefault(x => (x.Prop1 == Prop1Value && x.Prop2 == Prop2Value && x.Prop3 == Prop3Value)
    || (x.Prop1 == Prop1Value && x.Prop2 == Prop2Value)
    || (x => x.Prop1 == Prop1Value));
}

C＃查找最佳匹配元素/简化查询到列表

2 个答案: