Question

One has txtDateReceived and second has txtVendorPackDate. Before insert will add record I have to check if txtDateReceived is not erlier then txtVendorPackDate. I try use TextChanged event.

protected void txtVendorPackDate_TextChanged(object sender, EventArgs e)
{
    DateTime fromDate = DateTime.MinValue;
    DateTime toDate = DateTime.MaxValue;
    bool parseResultMin = DateTime.TryParse(txtVendorPackDate.Text, out fromDate);
    bool parseResultMax = DateTime.TryParse(txtDateReceived.Text, out toDate);
    if (toDate < fromDate)
    {
        txtVendorPackDate.Text = "";
        lblDateExpired.Visible = true;
        lblDateExpired.Text = "Selected date is incorrect, please enter correct data.";
        txtVendorFatPerc.Focus();
    }

    double expired = toDate.Subtract(fromDate).TotalDays;

    if (expired >= 60)
    {

        lblDateExpired.Text = "Date Expired " + expired + " days after pack day!!!" 
        lblDateExpired.Visible = true;
    }  
} 

How I could do it from client side not using controls validation.

Answer 1

Try this

if (!parseResultMin || !parseResultMax || toDate < fromDate)

In your code, if both dates are invalid, toDate and fromDate will both be DateTime.MinValue, so the expression toDate < fromDate won’t be true.