如何从C#中的文件中删除所有字符实例？

Question

我正在处理来自第三方的XML文件.这些文件偶尔会在其中包含无效字符,从而导致XMLTextReader.Read()异常.

我目前使用以下函数处理此问题:

XmlTextReader GetCharSafeXMLTextReader(string fileName)
{
    try
    {
        MemoryStream ms = new MemoryStream();
        StreamReader sr = new StreamReader(fileName);
        StreamWriter sw = new StreamWriter(ms);
        string temp;
        while ((temp = sr.ReadLine()) != null)
            sw.WriteLine(temp.Replace(((char)4).ToString(), "").Replace(((char)0x14).ToString(), ""));

        sw.Flush();
        sr.Close();
        ms.Seek(0, SeekOrigin.Begin);
        return new XmlTextReader(ms);
    }
    catch (Exception exp)
    {
        throw new Exception("Error parsing file: " + fileName + " " + exp.Message, exp.InnerException);
    }
}

我的直觉是说应该有一个更好/更快的方法来做到这一点.(是的,让第三方修复他们的XML会很棒,但目前还没有发生.)

编辑:这是最终解决方案,基于cfeduke的答案:

    public class SanitizedStreamReader : StreamReader
    {
        public SanitizedStreamReader(string filename) : base(filename) { }
        /* other ctors as needed */
        // this is the only one that XmlTextReader appears to use but
        // it is unclear from the documentation which methods call each other
        // so best bet is to override all of the Read* methods and Peek
        public override string ReadLine()
        {
            return Sanitize(base.ReadLine());
        }

        public override int Read()
        {
            int temp = base.Read();
            while (temp == 0x4 || temp == 0x14)
                temp = base.Read();
            return temp;
        }

        public override int Peek()
        {
            int temp = base.Peek();
            while (temp == 0x4 || temp == 0x14)
            {
                temp = base.Read();
                temp = base.Peek();
            }
            return temp;
        }

        public override int Read(char[] buffer, int index, int count)
        {
            int temp = base.Read(buffer, index, count);
            for (int x = index; x < buffer.Length; x++)
            {
                if (buffer[x] == 0x4 || buffer[x] == 0x14)
                {
                    for (int a = x; a < buffer.Length - 1; a++)
                        buffer[a] = buffer[a + 1];
                    temp--; //decrement the number of characters read
                }  
            }
            return temp;
        }

        private static string Sanitize(string unclean)
        {
            if (unclean == null)
                return null;
            if (String.IsNullOrEmpty(unclean))
                return "";
            return unclean.Replace(((char)4).ToString(), "").Replace(((char)0x14).ToString(), "");
        }
    }

Answer 1

消毒数据很重要.有时边缘情况 - "XML"中的无效字符 - 确实发生.你的解决方案是对的.如果你想要一个适合.NET框架的解决方案来重新构建你的代码以适应它自己的Stream:

public class SanitizedStreamReader : StreamReader {
  public SanitizedStreamReader(string filename) : base(filename) { }
  /* other ctors as needed */

  // it is unclear from the documentation which methods call each other
  // so best bet is to override all of the Read* methods and Peak
  public override string ReadLine() {
    return Sanitize(base.ReadLine());
  }

  // TODO override Read*, Peak with a similar logic as this.ReadLine()
  // remember Read(Char[], Int32, Int32) to modify the return value by
  // the number of removed characters

  private static string Sanitize(string unclean) {
    if (String.IsNullOrEmpty(unclean)
      return "";
    return unclean.Replace(((char)4).ToString(), "").Replace(((char)0x14);
  }
}

有了这个新的,SanitizedStreamReader你就可以根据需要将它链接到处理流中,而不是依靠一个神奇的方法来清理东西并为你呈现一个XmlTextReader:

return new XmlTextReader(new SanitizedStreamReader("filename.xml"));

不可否认,这可能比必要的工作更多,但您将从这种方法中获得灵活性.