ASP.NET WebForms to React: pull rules out of ViewState, validators and code-behind

1// Quote.aspx: <asp:RangeValidator ControlToValidate="txtCoverage"
2//   Type="Currency" MinimumValue="10000" MaximumValue="500000" />
3protected void Page_Load(object sender, EventArgs e)
4{
5    if (!IsPostBack)
6    {
7        ViewState["Tier"] = GetCustomerTier(Request.QueryString["cid"]);
8    }
9}
10 
11protected void btnQuote_Click(object sender, EventArgs e)
12{
13    if (!Page.IsValid) return;
14    decimal coverage = decimal.Parse(txtCoverage.Text);
15    string tier = (string)ViewState["Tier"];
16    decimal rate = tier == "GOLD" ? 0.m : 0.m;
17    if (chkSmoker.Checked) rate += 0.m;
18    lblPremium.Text = Math.Round(coverage * rate, 2).ToString("C");
19}

1paths:
2  /quotes:
3    post:
4      operationId: createQuote
5      x-pyd-source: Quote.aspx.cs:3-19
6      x-pyd-decision: QUOTE-RATE-02
7      requestBody:
8        content:
9          application/json:
10            schema:
11              type: object
12              required: [customerId, coverage]
13              properties:
14                customerId:
15                  type: string
16                  description: was query string cid
17                coverage:
18                  type: number
19                  minimum: 10000
20                  maximum: 500000
21                smoker: { type: boolean, default: false }
22      responses:
23        "200":
24          content:
25            application/json:
26              schema:
27                properties:
28                  premium:
29                    type: number
30                    x-pyd-rounding: half-even, 2 dp
31# QUOTE-RATE-02: tier GOLD 0.0042, any other 0.0055;
32#   smoker +0.0030. Tier was read from ViewState.