Multiply dynamic ASP.Net TextBox price based on condition using C# and VB.Net

Hi

this code below is an example of customer item order which multiplies the price by the quantity of item purchased by customer.

But i want to add this, if 0.5 is inserted into the QTY let the resullt be multiplied by 2.

That is if $50(price) X 5(QTY) SUM = $250, what i want to add if the QTY is 0.5 multiply by 2

example $50(price) x QTY(0.5)= $25 X 2 =$50

So if the inserted QTY is 0.5 then multiply the result by 2 like the above example

 HTML

<table>
    <tr>
        <td>Item</td>
        <td>Price</td>
        <td>Qty</td>
    </tr>
    <tr>
        <td><asp:TextBox ID="txtItem" runat="server" CssClass="form-control" /></td>
        <td><asp:TextBox ID="TextBox1" runat="server" CssClass="form-control" /></td>
        <td><asp:TextBox ID="txtQuantity" runat="server" CssClass="form-control" /></td>
        <td><asp:Button ID="btnRemove" runat="server" OnClick="btnRemove_Click" Text="Remove" CssClass="btn btn-warning" /></td>
    </tr>
</table>

<asp:GridView runat="server" ID="gvInsertedRecords" CssClass="datatable-dashv1-list custom-datatable-overright table table-hover" AutoGenerateColumns="False">
    <Columns>
        <asp:TemplateField HeaderText="Item" SortExpression="Item">
            <EditItemTemplate>
                <asp:TextBox ID="TextBox2" runat="server" Text='<%# Bind("Item") %>'></asp:TextBox>
            </EditItemTemplate>
            <ItemTemplate>
                <asp:Label ID="Label2" runat="server" Text='<%# Bind("Item") %>'></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Price" SortExpression="Price">
            <EditItemTemplate>
                <asp:TextBox ID="TextBox3" runat="server" Text='<%# Bind("Price") %>'></asp:TextBox>
            </EditItemTemplate>
            <ItemTemplate>
                <asp:Label ID="Label3" runat="server" Text='<%# Bind("Price") %>'></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Quantity" SortExpression="Quantity">
            <EditItemTemplate>
                <asp:TextBox ID="TextBox4" runat="server" Text='<%# Bind("Quantity") %>'></asp:TextBox>
            </EditItemTemplate>
            <ItemTemplate>
                <asp:Label ID="Label4" runat="server" Text='<%# Bind("Quantity") %>'></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>
<asp:UpdatePanel ID="up1" runat="server">
    <ContentTemplate>
        <div class="">
        </div>
        <div>
            <table>
                <tr>
                    <td>
                        <asp:PlaceHolder ID="ph1" runat="server" />
                        <br />
                        <asp:Button ID="btnAdd" runat="server" Text="Add" CssClass="btn btn-primary" />
                    </td>
                </tr>
            </table>
        </div>
    </ContentTemplate>
</asp:UpdatePanel>
<br />
<br />
<asp:Literal ID="ltlCount" runat="server" Text="0" Visible="false" />
<asp:Literal ID="ltlRemoved" runat="server" Visible="false" />
<asp:Label ID="Label8" runat="server" Text="" Font-Bold="True" Font-Size="X-Large" ForeColor="Red"></asp:Label>
<div class=" pull-right">
    <asp:Button Text="Submit" runat="server" OnClick="OnSave" CssClass="btn btn-default" />
    <asp:Button Text="Calculate" runat="server" OnClick="Calculate" CssClass="btn btn-info" />
</div>
<div class="clearfix"></div>
<hr />

Code

protected void OnSave(object sender, EventArgs e)
{
    if (Page.IsValid)
    {
        if (txtrecipt.Text == "")
        {
            ClientScript.RegisterClientScriptBlock(this.GetType(), "alert", "<script>alert('Enter Recipt ... !!')</script>", false);
        }
        else
        {
            DataTable dt = new DataTable();
            dt.Columns.AddRange(new DataColumn[] { new DataColumn("Item"), new DataColumn("Price"), new DataColumn("Quantity") });
            int i = 1;
            foreach (Control c in ph1.Controls)
            {
                if (c.GetType().Name.ToLower() == "usercontrol_ascx")
                {
                    UserControl uc = (UserControl)c;
 
                    TextBox tbItem = uc.FindControl("txtItem") as TextBox;
                    TextBox tbPrice = uc.FindControl("txtPrice") as TextBox;
                    TextBox tqty = uc.FindControl("txtQuantity") as TextBox;
                    TextBox half = uc.FindControl("txthalf") as TextBox;
                    if (!string.IsNullOrEmpty(tbItem.Text.Trim()) && !string.IsNullOrEmpty(tbPrice.Text.Trim()) && !string.IsNullOrEmpty(tqty.Text.Trim()) && !string.IsNullOrEmpty(half.Text.Trim()))
                    {
                        //dt.Rows.Add(tbItem.Text.Trim(), tbPrice.Text.Trim(), tqty.Text.Trim());
                        int availableQuantity = 0;
                        if (!string.IsNullOrEmpty(GetAvailableQuantity(tbItem.Text.Trim())))
                        {
                            availableQuantity = Convert.ToInt32(GetAvailableQuantity(tbItem.Text.Trim()));
                        }
 
                        if (Convert.ToInt32(tqty.Text.Trim()) > availableQuantity)
                        {
                            ScriptManager.RegisterClientScriptBlock(sender as Button, (sender as Button).GetType(), "alert" + i.ToString(), "<script>alert('No of Quantity entered is not available in Stock')</script>", false);
                        }
                        else
                        {
                            dt.Rows.Add(tbItem.Text.Trim(), tbPrice.Text.Trim(), tqty.Text.Trim());
                            int inserted = Insert(tbItem.Text.Trim(), tbPrice.Text.Trim(), tqty.Text.Trim());
                            if (inserted > 0)
                            {
                                UpdateStock(tbItem.Text.Trim(), tqty.Text.Trim());
                                ClientScript.RegisterClientScriptBlock(this.GetType(), "", "alert('Data Submitted Successfully ... !!')", true);
                            }
                        }
                    }
                }
            }
            // BindGridID();
            gvInsertedRecords.DataSource = dt;
            gvInsertedRecords.DataBind();
        }
    }
}
 
private string GetAvailableQuantity(string item)
{
    string availableQuantity = "";
    string constr = ConfigurationManager.ConnectionStrings["DB"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constr))
    { 
        string query = "SELECT Qty_Remaining FROM Store_Table WHERE Item = @Item AND Store=@Store";
        using (SqlCommand cmd = new SqlCommand(query))
        {
            cmd.Connection = con;
            cmd.Parameters.AddWithValue("@Store", Department.SelectedItem.Text);
            cmd.Parameters.AddWithValue("@Item", item);
            con.Open();
            availableQuantity = Convert.ToString(cmd.ExecuteScalar());
            con.Close();
        }
    }
 
    return availableQuantity;
}
private int Insert(string item, string price, string qty)
{
    int i = 0;
    string constr = ConfigurationManager.ConnectionStrings["DB"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constr))
    {
        string query = "INSERT INTO ItemOrdered (Store,SellsPerson,Receipt,Item,Price,Quantity,Sum) VALUES (@Store,@SellsPerson,@Receipt,@Item, @Price, @Quantity,@Sum)"; 
        using (SqlCommand cmd = new SqlCommand(query))
        {
            cmd.Connection = con;
            cmd.Parameters.AddWithValue("@Store", Department.SelectedItem.Text);
            cmd.Parameters.AddWithValue("@SellsPerson", HttpContext.Current.User.Identity.Name);
            cmd.Parameters.AddWithValue("@Receipt", txtrecipt.Text);
            cmd.Parameters.AddWithValue("@Item", item);
            cmd.Parameters.AddWithValue("@Price", price);
            cmd.Parameters.AddWithValue("@Quantity", qty);
            cmd.Parameters.AddWithValue("@Sum", Convert.ToDecimal(price) * Convert.ToDecimal(qty));
            con.Open();
            i = cmd.ExecuteNonQuery();
            con.Close(); 
        }
    }
 
    return i; 
}