Saving class properties across several events?

[Sodapop]

Hi, I am currently coding a web form that takes an address and verifies it with the United States Postal Service before inserting the record into a MS Access Database. Along with this, I have a checkbox (with AutoPostBack) that verifies and saves the content in the text boxes as billing information in a customer class before clearing the text fields to enter in the shipping info (newCustomer.sFirstName property for shipping vs. newCustomer.firstName for billing & shipping). My problem lies when I click the checkbox to verify and 'save' the billing address and re-enter the address. The data for the first address gets set to null and I get an error. (cannot enter null into database)

What can I do to prevent (or enable) to properly set the data to the customer class properties without getting wiped across events? Here is my code thus far:

protected void btnSubmit_Click(object sender, EventArgs e)
    {
        Customer existCust = new Customer();
 
        blowinDT = new dsSMOOTH.SG_Sub_Invoice_CardsDataTable();
        blowinTA = new dsSMOOTHTableAdapters.SG_Sub_Invoice_CardsTableAdapter();
        blowinDT = blowinTA.GetData();
 
        MAX.USPS.USPSManager m = new MAX.USPS.USPSManager("726STARM2333", true);
        MAX.USPS.Address a = new MAX.USPS.Address();
        a.Address2 = txtAddress.Text;
        a.City = txtCity.Text;
        a.State = txtState.Text;
        MAX.USPS.Address validatedAddress = m.ValidateAddress(a);
        if (validatedAddress == null)
        {
            lblError.ForeColor = System.Drawing.Color.Red;
            lblError.Text = "The address entered was invalid";
        }
        else
        {
            if (chkSameAdd.Checked == true)
            {
                newCust.SInstID = txtInstID.Text;
                newCust.SFirstName = txtFName.Text;
                newCust.SLastName = txtLName.Text;
                newCust.SMiddleInitial = txtMiddleInitial.Text;
                newCust.SAddress = validatedAddress.Address2;
                newCust.Address2 = txtAddress2.Text;
                newCust.SCity = validatedAddress.City;
                newCust.SState = validatedAddress.State;
                newCust.SZip = Convert.ToDouble(validatedAddress.Zip);
                newCust.Insert(newCust);
 
                lblError.ForeColor = System.Drawing.Color.Green;
                if (newCust.SFirstName != null)
                    lblError.Text = "Address Information for " + newCust.FirstName + ", " + newCust.LastName + " and " + newCust.SFirstName + ", " + newCust.SLastName + " has been validated and saved to the database! Ready for next entry.";
 
                txtFName.Text = "";
                txtLName.Text = "";
                txtInstID.Text = "";
                txtMiddleInitial.Text = "";
                txtAddress.Text = "";
                txtAddress2.Text = "";
                txtCity.Text = "";
                txtState.Text = "";
                txtZip.Text = "";
                txtPhone.Text = "";
                txtEmail.Text = "";
                txtBlowIn.Text = "";
            }
            else
            {
                newCust.FirstName = txtFName.Text;
                newCust.LastName = txtLName.Text;
                newCust.Address = validatedAddress.Address2;
                newCust.City = validatedAddress.City;
                newCust.State = validatedAddress.State;
                newCust.Zip = validatedAddress.Zip + "-" + validatedAddress.ZipPlus4;
                    newCust.InstID = txtInstID.Text;
                    newCust.Address2 = txtAddress2.Text;
                    newCust.BlowInIssue = txtBlowIn.Text;
                    newCust.Email = txtEmail.Text;
                    newCust.MiddleInitial = txtMiddleInitial.Text;
                    double phone = Convert.ToDouble(txtPhone.Text);
                    newCust.Phone = String.Format("{0:(###)###-####}", phone);
                    if (chkSameAdd.Checked == false)
                    {
                        newCust.CloneAddress = true;
                        newCust.SFirstName = "";
                        newCust.SLastName = "";
                        newCust.SMiddleInitial = "";
                        newCust.SInstID = "";
                        newCust.SAddress = "";
                        newCust.SAddress2 = "";
                        newCust.SCity = "";
                        newCust.SState = "";
                    }
                    newCust.Insert(newCust);
 
                    lblError.ForeColor = System.Drawing.Color.Green;
                    if (newCust.SFirstName != null)
                        lblError.Text = "Address information for " + newCust.LastName + ", " + newCust.FirstName + " has been validated and saved to the database! Ready for next entry.";
 
                    txtFName.Text = "";
                    txtLName.Text = "";
                    txtInstID.Text = "";
                    txtMiddleInitial.Text = "";
                    txtAddress.Text = "";
                    txtAddress2.Text = "";
                    txtCity.Text = "";
                    txtState.Text = "";
                    txtZip.Text = "";
                    txtPhone.Text = "";
                    txtEmail.Text = "";
                    txtBlowIn.Text = "";
                }
            }
        }
 
    protected void chkSameAdd_CheckedChanged(object sender, EventArgs e)
    {
        if (txtFName.Text != string.Empty && txtLName.Text != string.Empty && txtAddress.Text != string.Empty && txtCity.Text != string.Empty && txtState.Text != string.Empty && txtZip.Text != string.Empty)
        {
            Customer existCust = new Customer();
 
            blowinDT = new dsSMOOTH.SG_Sub_Invoice_CardsDataTable();
            blowinTA = new dsSMOOTHTableAdapters.SG_Sub_Invoice_CardsTableAdapter();
            blowinDT = blowinTA.GetData();
 
            MAX.USPS.USPSManager m = new MAX.USPS.USPSManager("726STARM2333", true);
            MAX.USPS.Address a = new MAX.USPS.Address();
            a.Address2 = txtAddress.Text;
            a.City = txtCity.Text;
            a.State = txtState.Text;
            MAX.USPS.Address validatedAddress = m.ValidateAddress(a);
            if (validatedAddress == null)
            {
                lblError.ForeColor = System.Drawing.Color.Red;
                lblError.Text = "The address entered was invalid";
            }
            else
            {
                newCust.FirstName = txtFName.Text;
                newCust.LastName = txtLName.Text;
                newCust.MiddleInitial = txtMiddleInitial.Text;
                newCust.Address = validatedAddress.Address2;
                newCust.City = validatedAddress.City;
                newCust.State = validatedAddress.State;
                newCust.Zip = validatedAddress.Zip;
                newCust.Email = txtEmail.Text;
                double phone = Convert.ToDouble(txtPhone.Text);
                newCust.Phone = String.Format("{0:(###)###-####}", phone);
                newCust.CloneAddress = true;
                newCust.Address2 = txtAddress2.Text;
 
                    lblError.ForeColor = System.Drawing.Color.Green;
                    lblError.Text = "Billing information for " + newCust.FirstName + " " + newCust.LastName + " has been saved. Please enter the shipping information now.";
                    txtFName.Text = "";
                    txtLName.Text = "";
                    txtInstID.Text = "";
                    txtMiddleInitial.Text = "";
                    txtAddress.Text = "";
                    txtAddress2.Text = "";
                    txtCity.Text = "";
                    txtState.Text = "";
                    txtZip.Text = "";
                    txtPhone.Text = "";
                    txtEmail.Text = "";
 
            }
        }
        else
        {
            lblError.ForeColor = System.Drawing.Color.Red;
            lblError.Text = "Please fill out the necessary fields";
            chkSameAdd.Checked = false;
        }
    }
}

Sorry for the sloppy coding! I'm an amateur, If anyone has any suggestions on how to clean it up, I'm all open!

[ThatThatGuy]

@Sodapop
Yeah... that code looks real sloppy...

Have you set the ViewState property of the textbox controls to True..

[Sodapop]

view state's are all set to true. Working on cleaning up the code