/// <summary> 
/// 截取文本，区分中英文字符，中文算两个长度，英文算一个长度
/// </summary>
/// <param name="str">待截取的字符串</param>
/// <param name="length">需计算长度的字符串</param>
/// <returns>string</returns>
public static string GetSubString(string str, int length)
{
  string temp = str;
  int j = 0;
  int k = 0;
  for (int i = 0; i < temp.Length; i++)
  {
 if (Regex.IsMatch(temp.Substring(i, 1), @"[\u4e00-\u9fa5]+"))
 {
   j += 2;
 }
 else
 {
   j += 1;
 }
 if (j <= length)
 {
   k += 1;
 }
 if (j > length)
 {
   return temp.Substring(0, k) + "..";
 }
  }
  return temp;
}