using MongoDB.Driver; using System;  /// <summary> /// The result of a delete operation. /// </summary> public abstract class DeleteResult {  /// <summary>  /// The result of an acknowledged delete operation.  /// </summary>  public class Acknowledged : DeleteResult  {   private readonly long _deletedCount;    /// <inheritdoc />   public override long DeletedCount => _deletedCount;    /// <inheritdoc />   public override bool IsAcknowledged => true;    /// <summary>   /// Initializes a new instance of the <see cref="T:MongoDB.Driver.DeleteResult.Acknowledged" /> class.   /// </summary>   /// <param name="deletedCount">The deleted count.</param>   public Acknowledged (long deletedCount);  }   /// <summary>  /// The result of an unacknowledged delete operation.  /// </summary>  public class Unacknowledged : DeleteResult  {   private static Unacknowledged __instance = new Unacknowledged ();    /// <summary>   /// Gets the instance.   /// </summary>   public static Unacknowledged Instance => __instance;    /// <inheritdoc />   public override long DeletedCount {    get;   }    /// <inheritdoc />   public override bool IsAcknowledged => false;    private Unacknowledged ();  }   /// <summary>  /// Gets the deleted count. If IsAcknowledged is false, this will throw an exception.  /// </summary>  public abstract long DeletedCount {   get;  }   /// <summary>  /// Gets a value indicating whether the result is acknowledged.  /// </summary>  public abstract bool IsAcknowledged {   get;  }   internal static DeleteResult FromCore (BulkWriteResult result); }  

上面的 Acknowleged 继承于 DeleteResult 可以是为啥要写到 DeleteResult 之中？岂不是造成循环了？