C#实现根据字节数截取字符串并加上省略号的方法

程序员文章站 2023-12-18 15:54:28

本文实例讲述了c#按字节数截取字符串并在后面加上省略号...的方法，这是一个自定义的c#函数，函数的使用说明如下：

<param name="origstr">原始字符串</param>
<param name="endindex">提取前endidex个字节</param>
<returns></returns>

函数代码如下：

public static string getsubstring(string origstr, int endindex)
{
  if (origstr == null || origstr.length == 0 || endindex < 0)
    return "";
  int bytescount = system.text.encoding.getencoding("gb2312").getbytecount(origstr);
  if (bytescount > endindex)
  {
    int readylength = 0;
    int bytelength;
    for (int i = 0; i < origstr.length; i++)
    {
      bytelength = system.text.encoding.getencoding("gb2312").getbytecount(new char[] { origstr[i] });
      readylength += bytelength;
      if (readylength == endindex)
      {
        origstr = origstr.substring(0, i + 1) + "...";
        break;
      }
      else if (readylength > endindex)
      {
        origstr = origstr.substring(0, i) + "...";
        break;
      }
    }
  }
  return origstr;
}

以下所示示例也是根据字节数截取字符串的，只是这个函数后面不加省略号……

/// 按字节数截取字符串(不带省略号)
/// </summary>
/// <param name="origstr">原始字符串</param>
/// <param name="endindex">提取前endidex个字节</param>
/// <returns></returns>
public static string getsub1string(string origstr, int endindex)
{
  if (origstr == null || origstr.length == 0 || endindex < 0)
    return "";
  int bytescount = system.text.encoding.getencoding("gb2312").getbytecount(origstr);
  if (bytescount > endindex)
  {
    int readylength = 0;
    int bytelength;
    for (int i = 0; i < origstr.length; i++)
    {
      bytelength = system.text.encoding.getencoding("gb2312").getbytecount(new char[] { origstr[i] });
      readylength += bytelength;
      if (readylength == endindex)
      {
        origstr = origstr.substring(0, i + 1);
        break;
      }
      else if (readylength > endindex)
      {
        origstr = origstr.substring(0, i);
        break;
      }
    }
  }
  return origstr;
}