C# 在指定字符串中间插入换行符

public class StringUtility {

	public static string BreakLongString(string SubjectString, int lineLength)
	{
        StringBuilder sb = new StringBuilder(SubjectString);
		int offset = 0;
		ArrayList indexList = buildInsertIndexList(SubjectString, lineLength);
		for(int i=0;i<indexList.Count;i++){
			sb.Insert((int)indexList[i]+offset,'\n');
			offset++;
		}
        return sb.ToString();
	}
	
	public static bool IsChinese(char c){
	  return (int)c>=0x4E00 && (int)c<=0x9FA5;
	}
	
	private static ArrayList buildInsertIndexList(string str, int maxLen){
		int nowLen = 0;
		ArrayList list = new ArrayList();
		for(int i=1;i<str.Length;i++){
			if(IsChinese(str[i])){
				nowLen += 2;
			}else{
				nowLen ++;
			}
			if(nowLen > maxLen){
				nowLen = 0;
				list.Add(i);
			}
		}
		return list;
	}
}