string字符串20110725 asp.net里面怎么转换为2011-07-25这种格式？

[lj419300010]

string字符串20110725 asp.net里面怎么转换为2011-07-25这种格式？

[huangwenquan123]

str.Insert(4, "-").Insert(str.Length - 1, "-")

[ASPNETCHENGXU]

或者先转换成日期类型的在，改变格式

[threenewbee]

string dt = "20110725";
st = string.Format("{0}-{1}-{2}", dt.SubString(0, 4), dt.SubString(4, 2), dt.SubString(6));

[子夜__]

 protected void Page_Load(object sender, EventArgs e)
    {
        string str = "20110725";
        Response.Write(ConvertDate(str).ToString("yyyy-MM-dd"));
    }
    public DateTime ConvertDate(string strDate)
    {
        char[] dates = strDate.ToCharArray();
        string strresult = "";
        for (int i = 0; i < dates.Length; i++)
        {
            strresult += dates[i];
            if ((i + 1) % 2 == 0 && i != 1 && i != 0 && i != dates.Length - 1)
            {
                strresult += "-";
            }
        }
       return  Convert.ToDateTime(strresult);
      
    }