String was not recognized in valid datetime

Question

I tried with diffrent formats but still giving this exception.

I am trying to show datatable in gridview using select command.

I used Expense_Date column in sql server table as a date datatype.

My code is here.

  using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

using System.Data;
using System.Data.SqlClient;

public partial class ConsolidateByMonth : System.Web.UI.Page
{
    double grdTotal = 0;
    protected void Page_Load(object sender, EventArgs e)
    {

    }
protected void btnShowExpenses_Click(object sender, EventArgs e)
{
    string month = DropDownList1.Text;
    string NoOfMonth="";
    string days="";
    switch(month){
        case "January":
            NoOfMonth = "01";
            days = "31";
            break;
        case "Febuary":
            NoOfMonth = "02";
            days = "28";
            break;
        case "March":
            NoOfMonth = "03";
            days = "31";
            break;
        case "April":
            NoOfMonth = "04";
            days = "30";
            break;
         case "May":
            NoOfMonth = "05";
            days = "31";
            break;
        case "June":
            NoOfMonth = "06";
            days = "30";
            break;
        case "July":
            NoOfMonth = "07";
            days = "31";
            break;
        case "August":
            NoOfMonth = "08";
            days = "31";
            break;
         case "September":
            NoOfMonth = "09";
            days = "30";
            break;
        case "October":
            NoOfMonth = "10";
            days = "31";
            break;
        case "November":
            NoOfMonth = "11";
            days = "30";
            break;
        case "December":
            NoOfMonth = "12";
            days = "31";
            break;
    }
    string str1 = (NoOfMonth + "01" + DropDownList2.Text).ToString(); //04012014
    string str2 = (NoOfMonth + days + DropDownList2.Text).ToString();

    DateTime date1 = DateTime.ParseExact(str1, "yyyy-MM-dd", null);
    DateTime date2 = DateTime.ParseExact(str2, "yyyy-MM-dd", null);


    string con_string = "@data source=10.10.10.5; initial catalog= testAzhar; user=xx; password=xxxxx;";
    SqlConnection con = new SqlConnection(con_string);
    string qry = "Select Expense_Category, Expense_Description, Amount from CompanyExpenses3 where Expense_Date>=" + date1 + "and <=" + date2;
    SqlCommand cmd = new SqlCommand(qry, con);
    con.Open();
    SqlDataAdapter da = new SqlDataAdapter(cmd);
    DataTable dt = new DataTable();
    da.Fill(dt);
    GridView1.DataSource = dt;
    con.Close();

}

Please correct me.

Answer 1

Write something like this...

string str1 = (NoOfMonth + "/01/" + DropDownList2.Text).ToString(); //04012014
string str2 = (NoOfMonth +"/"+ days+"/" + DropDownList2.Text).ToString();

DateTime date1 = DateTime.ParseExact(str1, "MM/dd/yyyy", System.Globalization.CultureInfo.InvariantCulture);
DateTime date2 = DateTime.ParseExact(str2, "MM/dd/yyyy", System.Globalization.CultureInfo.InvariantCulture);