'String was not recognized as a valid DateTime.' in asmx.cs file of asp.net c#

Question

I have Two Input Type = "Date" and one Input Type = "Button"

<input type="date" runat="server" id="dtp_from" />
<input type="date" runat="server" id="dtp_to" />
<input type="button" id="btnSubmit" CssClass="custom-btn" value="Submit" />

One GridView Table

<table id="gv_Datatable" class="table table-responsive table-hover">
    <thead>
        <tr>
            <th>Id</th>
            <th>Date</th>
            <th>Name</th>
            <th>Description</th>
            <th>Receipt</th>
            <th>Payment</th>                            
            <th>Balance</th>
            <th>Actions</th>
        </tr>
    </thead>
    <tfoot>
        <tr>
            <th>Id</th>
            <th>Date</th>
            <th>Name</th>
            <th>Description</th>
            <th>Receipt</th>
            <th>Payment</th>
            <th>Balance</th>                            
        </tr>
    </tfoot>
</table>                

Now, here when click on button ajax method is called and through parameter two date are passing to the asmx.cs file.

$("#btnSubmit").click(function (e) {                
    var dataToSend = {
        param1: JSON.stringify(document.getElementById("<%=dtp_from.ClientID%>").value),
        param2: JSON.stringify(document.getElementById("<%=dtp_to.ClientID%>").value)
    };
    $.ajax({
        type: "POST",
        url: "FillGridMethod.asmx/CashBookList",
        data: dataToSend,
        dataType: "json",
        success: function (data) {                        
            var datatableVariable = $('#gv_Datatable').DataTable({
                dom: 'Bfrtip',
                data: data,
                columns: [
                    { 'data': 'Id', visible: false },
                    {
                        'data': 'cashbookdate', 'render': function (date) {
                            var date = new Date(parseInt(date.substr(6)));
                            var month = date.getMonth() + 1;
                            return date.getDate() + "/" + month + "/" + date.getFullYear();
                        }
                    },
                    { 'data': 'cashbookaccname' },
                    { 'data': 'cashbookdescription' },
                    { 'data': 'cashbookreceipt' },
                    { 'data': 'cashbookpayment' },
                    { 'data': 'Balance' },
                    {
                        "render": function (data, type, row) { return "<a href='#' class='btn btn-success' onclick=DeleteCustomer('" + row.Id + "');>View</>"; }
                    },
                    {
                        "render": function (data, row) { return "<a href='#' class='btn btn-danger'>Delete</a>"; }
                    }]
            });
        }
    });
});

Here is the asmx.cs file code

[WebMethod(enableSession: true)]
public void CashBookList(string param1, string param2)
{
    DateTime fromDate = DateTime.ParseExact(param1, "dd/MM/yyyy", CultureInfo.InvariantCulture);

    var cashBook = new List<CashBookModel>();
    string constr = cn.ConnectionString;
    using (SqlConnection con = new SqlConnection(constr))
    {
        qryFillGrid = " select cashbookid, cashbookdate, cashbookaccname, cashbookdescription, cashbookreceipt, cashbookpayment, Balance from tbl_cashbook " + System.Environment.NewLine;
        qryFillGrid += " where BranchID = " + HttpContext.Current.Session["BranchID"] + " " + System.Environment.NewLine;
        if (HttpContext.Current.Session["AccountMode"].ToString() != "ALL")
        {
            qryFillGrid += " and AccountMode = '" + HttpContext.Current.Session["AccountMode"].ToString() + "' " + System.Environment.NewLine;
        }
        if(param1 != "\"\"")
        {                    
            qryFillGrid += " and convert(varchar(10), convert(datetime, cashbookdate,105),112) >= '" + Convert.ToDateTime(service.IfNullThen(fromDate, DateTime.Now.Date)).Date.ToString("yyyyMMdd") + "' " + System.Environment.NewLine;
            if (param2 != "\"\"")
            {
                qryFillGrid += " and convert(varchar(10), convert(datetime, cashbookdate,105),112) <= '" + Convert.ToDateTime(service.IfNullThen(param2, DateTime.Now.Date)).Date.ToString("yyyyMMdd") + "' " + System.Environment.NewLine;
            }
        }
        else
        {
            qryFillGrid += " and convert(varchar(10), convert(datetime, cashbookdate,105),112) = '" + System.DateTime.Now.Date + "' " + System.Environment.NewLine;                    
        }
        qryFillGrid += " order by cashbookdate, cashbookid desc " + System.Environment.NewLine;
        var cmd = new SqlCommand(qryFillGrid, con);
        con.Open();
        var dr = cmd.ExecuteReader();
        while (dr.Read())
        {
            var cashBookModel = new CashBookModel
            {
                Id = Convert.ToInt32(dr[0]),
                cashbookdate = Convert.ToDateTime(dr[1]),
                cashbookaccname = dr[2].ToString(),
                cashbookdescription = dr[3].ToString(),
                cashbookreceipt = Convert.ToDecimal(service.IfNullThen(dr[4], 0)),
                cashbookpayment = Convert.ToDecimal(service.IfNullThen(dr[5], 0)),
                Balance = Convert.ToDecimal(service.IfNullThen(dr[6], 0)),
            };
            cashBook.Add(cashBookModel);
        }
    }
    var js = new JavaScriptSerializer();
    Context.Response.Write(js.Serialize(cashBook));
}

DateTime fromDate = DateTime.ParseExact(param1, "dd/MM/yyyy", CultureInfo.InvariantCulture);

In this below line of asmx.as file getting error i.e.: 'String was not recognized as a valid DateTime.'

Answer 1

@s.k.Soni

It should work. check this code.