Converting String to DateTime

 public void SetDate()
    {
 txt_FromDate.Text = "25/05/2013";
            string TodaysDate = System.DateTime.Now.ToString("dd/MM/yyyy");
            string[] dateArray = TodaysDate.Split(' ');
            txt_ToDate.Text = dateArray[0].ToString();
        DateTime FromDate = DateTime.ParseExact(txt_FromDate.Text, "dd/MM/yyyy", CultureInfo.InvariantCulture);
        string ModifiedFromDate = FromDate.AddDays(-1).ToString();
        string[] ModifiedFromDateArray = ModifiedFromDate.Split(' ');
        ModifiedFromDate = ModifiedFromDateArray[0].ToString();
        //Session["FromDate_Chart"] = ChangeDateFormat(ModifiedFromDate);
        Session["FromDate_Chart"] = ModifiedFromDate;

        DateTime ToDate = DateTime.ParseExact(txt_ToDate.Text, "dd/MM/yyyy", CultureInfo.InvariantCulture);
        string ModifiedToDate = ToDate.AddDays(1).ToString();
        string[] ModifiedToDateArray = ModifiedToDate.Split(' ');
        ModifiedToDate = ModifiedToDateArray[0].ToString();
        //Session["ToDate_Chart"] = ChangeDateFormat(ModifiedToDate);
        Session["ToDate_Chart"] = ModifiedToDate;
    }

    public string ChangeDateFormat(string Date)
    {
        try
        {
            string[] dateArray = Date.Split('/');
            Date = dateArray[1] + "/" + dateArray[0] + "/" + dateArray[2];
        }
        catch (Exception ex)
        {

        }
        return Date;


    }