Exception Details: System.FormatException: String was not recognized as a valid DateTime.

Question

Hi, i am getting above error, i am new to asp.net pls help

protected void btnSubmit_Click(object sender, EventArgs e)
    {
        double dstartcnt = 0; //string dstartcnt = string.Emptydouble dstartcnt = 0;
        string strStartDate = "03/22";
        string strbeforeDate = "03/21";
        string strStartCurrentyear = string.Empty;
        string strEndCurrentyear = string.Empty;
        string strStartCurrentMonth = string.Empty;
        string strEndCurrentMonth = string.Empty;
        double dEndCount = 0;
        DateTime SelectedDate;
        DateTime EndDate;
        DataTable objGridTable = new DataTable();
        double iResult = 0;
        double iMoreCnt = 0;
        double tempval = 0;

        try
        {
            if (!string.IsNullOrEmpty(this.ddlLocation.SelectedItem.Text))
            {
                if (!string.IsNullOrEmpty(this.StartDate.Text.ToString()) && Convert.ToDateTime(this.StartDate.Text).ToString("MM-dd").Equals("03-22"))
                {
                    dstartcnt = 1;
                    SelectedDate = Convert.ToDateTime(this.StartDate.Text);
                    EndDate = Convert.ToDateTime(this.EndDate.Text);
                    strEndCurrentyear = Convert.ToDateTime(this.EndDate.Text).Year.ToString();
                    dEndCount = EndDate.Subtract(Convert.ToDateTime(strStartDate + "/" + strEndCurrentyear)).TotalDays;

                }
                else if (!string.IsNullOrEmpty(this.StartDate.Text.ToString()))
                {
                    strStartCurrentyear = Convert.ToDateTime(this.StartDate.Text).Year.ToString();
                    strEndCurrentyear = Convert.ToDateTime(this.EndDate.Text).Year.ToString();
                    strStartCurrentMonth = Convert.ToDateTime(this.StartDate.Text).Month.ToString();
                    strEndCurrentMonth = Convert.ToDateTime(this.EndDate.Text).Month.ToString();

                    SelectedDate = Convert.ToDateTime(this.StartDate.Text);
                    EndDate = Convert.ToDateTime(this.EndDate.Text);
                    //SelectedDate = DateTime.Parse(this.StartDate.Text);
                    //EndDate = DateTime.Parse(this.EndDate.Text);
                    //if (Convert.ToDateTime(strStartDate + "/" + strStartCurrentyear) < )
                  // Here starting is -365 through if condition
                    //dstartcnt = SelectedDate.Subtract(Convert.ToDateTime(strStartDate + "/" + strStartCurrentyear)).TotalDays;
                    if (int.Parse(strStartCurrentMonth) >= 3 && SelectedDate.Day > 21)
                        dstartcnt = SelectedDate.Subtract(Convert.ToDateTime(strStartDate + "/" + strStartCurrentyear)).TotalDays + 1;
                    else if (int.Parse(strStartCurrentMonth) >= 3 && SelectedDate.Day < 22) // lessthan 22 madhu
                        dstartcnt = SelectedDate.Subtract(Convert.ToDateTime(strStartDate + "/" + strStartCurrentyear)).TotalDays + 365; // madhu
                    else if (int.Parse(strStartCurrentMonth) <= 3 && SelectedDate.Day < 22)
                    {
                        dstartcnt = SelectedDate.Subtract(Convert.ToDateTime(strStartDate + "/" + strStartCurrentyear)).TotalDays + 365;
                    }
                 //   else if (int.Parse(strStartCurrentMonth)
                   // dstartcnt = SelectedDate.Subtract(Convert.ToDateTime(this.StartDate.Text + "/" + strStartCurrentyear)).TotalDays;
                    if (int.Parse(strEndCurrentMonth) <=3 && EndDate.Day < 22)
                        dEndCount = EndDate.Subtract(Convert.ToDateTime(strStartDate + "/" + (int.Parse(strEndCurrentyear)-1).ToString())).TotalDays;
                    else if (int.Parse(strEndCurrentMonth) > 3)
                    {
                        dEndCount = -SelectedDate.Subtract(Convert.ToDateTime(strbeforeDate + "/" + strEndCurrentyear)).TotalDays + dstartcnt;
                        iMoreCnt = EndDate.Subtract(Convert.ToDateTime(strStartDate + "/" + strEndCurrentyear)).TotalDays + 1;
                    }
                }
                objGridTable.Columns.Add("Location", typeof(string));
                objGridTable.Columns.Add("Seleced Date", typeof(string));
                objGridTable.Columns.Add("Degree days", typeof(string));
                objGridTable.Columns.Add("Cumulative DD", typeof(double));
                objGridTable.Columns.Add("value", typeof(string));
        //        objGridTable.Columns.Add("NPP", typeof(double));

                int iDay = 0;
                tempval = 0;
                for (double i = dstartcnt; i <= dEndCount; i++)
                {
                    iResult = CalculateResult(i);
                    objGridTable.Rows.Add(this.ddlLocation.SelectedItem.Text, Convert.ToDateTime(this.StartDate.Text).AddDays(iDay).ToString("dd-M-yyyy"), iResult.ToString("0.###"), tempval + iResult, i);//hrs - iResult
                    tempval = iResult + tempval;
                    iDay++;
                }


                if (iMoreCnt > 0)
                {
                    //  tempval = 0;
                    for (double i = dstartcnt; i <= iMoreCnt; i++)
                    {
                        iResult = CalculateResult(i);
                        //  objGridTable.Rows.Add(this.ddlLocation.SelectedItem.Text, Convert.ToDateTime(strStartDate + "/" + strEndCurrentyear).AddDays(i - 1).ToString("dd-M-yyyy"), iResult, iResult + tempval);
                        objGridTable.Rows.Add(this.ddlLocation.SelectedItem.Text, Convert.ToDateTime(strStartDate + "/" + strEndCurrentyear).AddDays(i - 1).ToString("dd-M-yyyy"), iResult.ToString("0.###"), tempval + iResult, i); //, hrs - iResult
                        tempval = iResult + tempval;
                    }
                }
                    if (dstartcnt < 365.0) //madhu
                    {
                        for (double i = 0; i <= iMoreCnt; i++) // i = 0
                        {
                            iResult = CalculateResult(i);
                            //  objGridTable.Rows.Add(this.ddlLocation.SelectedItem.Text, Convert.ToDateTime(strStartDate + "/" + strEndCurrentyear).AddDays(i - 1).ToString("dd-M-yyyy"), iResult, iResult + tempval);
                            objGridTable.Rows.Add(this.ddlLocation.SelectedItem.Text, Convert.ToDateTime(strStartDate + "/" + strEndCurrentyear).AddDays(i - 1).ToString("dd-M-yyyy"), iResult.ToString("0.###"), tempval + iResult, i); //, hrs - iResult
                            tempval = iResult + tempval;
                        }
                    }// madhu
                if (objGridTable.Rows.Count > 0)
                {
                    GridDataResult.DataSource = objGridTable;
                    GridDataResult.DataBind();
                }
            }
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }

Answer 1

Please tell us which line is generating the error..

---

João Antonio Marques

Answer 2

Your sample dates are not DTs but month-year combinations.  If you try to convert any of them or if you enter the same values in a textbox (which it looks like StartDate is) then conversion will fail.  Dates must be a full month-day-year format. 

Your code is overly complex which is making it harder to figure out what is going on.  Here's my recommendation for simplifying it:

• Avoid Convert as it is a 1.x feature.  As of v2 you should be using the type-specific Parse or TryParse methods.
• Use DateTime.TryParse to convert from a string to a DateTime (or any primitive) when you are not sure if the conversion is allowed.  Never trust user input so any user input should be assumed to be wrong.
• Conversion is expensive compared to other operations so do it only once.  You are continually converting StartDate.Text to a DT just so you can access one of the fields.  Early in your method call DateTime.TryParse on StartDate.Text and then store the result in a local variable (i.e. startDate).  Reference the (converted) local variable's properties instead of doing the conversion each time.
• Stop converting everything to a string.  This is also expensive compared to simply comparing against real values.  For example you are getting the year and month properties but converting them to a string.  Later you want to do a comparison so you use Int32.Parse to convert them back.  You can just reference the properties directly without any need for storing them or converting them: 

protected void btnSubmit_Click(object sender, EventArgs e)
{
   if (ddlLocation....) 
   {    
      DateTime startDate, endDate;
      if (!DateTime.TryParse(StartDate.Text, out startDate) || !DateTime.TryParse(EndDate.Text, out endDate))
         //Error
      
      //Not sure why you have these hard coded values or 
      //what they mean 
      if (startDate.Month == 3 && startDate.Day = 22)
      {
         var endCount = //Get total days since???
         ...

Michael Taylor
http://msmvps.com/blogs/p3net