c# DirectoryInfo和Except

Question

我执行以下代码，结果令我费解

System.IO.DirectoryInfo rootDir = 
      new System.IO.DirectoryInfo(@"\\share\data");

// AllDir  == 10 folders

System.IO.DirectoryInfo[] AllDir = 
      rootDir.GetDirectories("*.*", SearchOption.AllDirectories);

// JackDir  == 2 folders

System.IO.DirectoryInfo[] JackDir = 
      rootDir.GetDirectories("Jack*.*", SearchOption.AllDirectories);

// MaryDir == 3 folders

System.IO.DirectoryInfo[] MaryDir = 
      rootDir.GetDirectories("Mary*.*", SearchOption.AllDirectories);

System.IO.DirectoryInfo[] otherDirectory = 
      AllDir.Except<DirectoryInfo>(MaryDir).Except(JackDir).ToArray();

而otherDirectory到底还有10 folders...why不是5？我怎样才能做到这一点？

Answer 1

您正在比较DirectoryInfo实例。它们与对GetDirectories的不同调用返回的不一样。

您可以为DirectoryInfo比较FullName定义自己的比较器，并在调用Except时使用它。

public class DirectoryInfoComparer : IEqualityComparer<System.IO.DirectoryInfo>
{
  public bool Equals(System.IO.DirectoryInfo x, System.IO.DirectoryInfo y)
  {
    if (object.ReferenceEquals(x, y))
      return true;
    if (x == null || y == null)
      return false;
    return x.FullName == y.FullName;
  }

  public int GetHashCode(System.IO.DirectoryInfo obj)
  {
    if (obj == null)
      return 0;
    return obj.FullName.GetHashCode();
  }
}


System.IO.DirectoryInfo[] otherDirectory = 
      AllDir.Except<DirectoryInfo>(MaryDir, new DirectoryInfoComparer()).Except(JackDir, new DirectoryInfoComparer()).ToArray();

Answer 2

您需要提供一个自定义比较器，您可以看到这种行为，因为它被测试为与“引用比较”相等，当然它们是不同的引用。

使用除方法过载外，该方法以IEqualityComparer为参数来实现所需的输出。