IDisposable 接口

提供一种用于释放非托管资源的机制。

地址：https://docs.microsoft.com/zh-cn/dotnet/api/system.idisposable?view=netframework-4.8

标题：IDisposable 接口

using System;
using System.IO;
using System.Text.RegularExpressions;

public class WordCount
{
   private String filename = String.Empty;
   private int nWords = 0;
   private String pattern = @"w+"; 

   public WordCount(string filename)
   {
      if (! File.Exists(filename))
         throw new FileNotFoundException("The file does not exist.");
      
      this.filename = filename;
      string txt = String.Empty;
      using (StreamReader sr = new StreamReader(filename)) {
         txt = sr.ReadToEnd();
      }
      nWords = Regex.Matches(txt, pattern).Count;
   }
   
   public string FullName
   { get { return filename; } }
   
   public string Name
   { get { return Path.GetFileName(filename); } }
   
   public int Count 
   { get { return nWords; } }
}

using语句实际上是语法上的便利。 在编译时, 语言编译器将为try / finally块实现中间语言 (IL)。

有关using语句的详细信息, 请参阅using 语句或using 语句主题。

Try/Finally 块

如果编程语言不支持像或using Visual Basic 中C#的语句这样的构造, 或者不想使用它, IDisposable.Dispose则可以从finally try /语句。 finally 下面的示例将上using一示例try / finally中的块替换为块。

using System;
using System.IO;
using System.Text.RegularExpressions;

public class WordCount
{
   private String filename = String.Empty;
   private int nWords = 0;
   private String pattern = @"w+"; 

   public WordCount(string filename)
   {
      if (! File.Exists(filename))
         throw new FileNotFoundException("The file does not exist.");
      
      this.filename = filename;
      string txt = String.Empty;
      StreamReader sr = null;
      try {
         sr = new StreamReader(filename);
         txt = sr.ReadToEnd();
      }
      finally {
         if (sr != null) sr.Dispose();     
      }
      nWords = Regex.Matches(txt, pattern).Count;
   }
   
   public string FullName
   { get { return filename; } }
   
   public string Name
   { get { return Path.GetFileName(filename); } }
   
   public int Count 
   { get { return nWords; } }
}