Insert into database after calculation in ASP.Net TextBox using C# and VB.Net

Hi Akhter,

Please refer below sample.

HTML

<table>
    <tr>
        <td>Weight</td>
        <td><asp:TextBox ID="txtWeight" runat="server" onkeyup="multiply()"></asp:TextBox></td>
        <td>* Rate</td>
        <td><asp:TextBox ID="txtrate" runat="server" onkeyup="multiply()"></asp:TextBox></td>
        <td>+ Freight</td>
        <td><asp:TextBox ID="txtfrghtamt" runat="server" onkeyup="multiply()"></asp:TextBox></td>
        <td>/&nbsp; To Weight</td>
        <td><asp:TextBox ID="txtWeightto" runat="server" onkeyup="multiply()"></asp:TextBox></td>
        <td>Total</td>
        <td><asp:TextBox ID="txtvalue" runat="server"></asp:TextBox></td>
    </tr>
    <tr>
        <td colspan="10" style="text-align: center">
            <asp:Button Text="Save" runat="server" OnClick="Save" /></td>
    </tr>
</table>

<script type="text/javascript">
    function multiply() {
        var txt1 = document.getElementById('<%= txtWeight.ClientID %>').value;
        var txt2 = document.getElementById('<%= txtrate.ClientID %>').value;
        var txt3 = document.getElementById('<%= txtfrghtamt.ClientID %>').value;
        var txt4 = document.getElementById('<%= txtWeightto.ClientID %>').value;
        if (isNaN(txt1) || txt1 == "") {
            txt1 = "0";
        }
        if (isNaN(txt2) || txt2 == "") {
            txt2 = "0";
        }
        if (isNaN(txt3) || txt3 == "") {
            txt3 = "0";
        }
        if (isNaN(txt4) || txt4 == "") {
            txt4 = "1";
        }
        var result = ((parseFloat(txt1) * parseFloat(txt2)) + parseFloat(txt3)) / parseFloat(txt4);
        var rstTxtbox = document.getElementById('<%= txtvalue.ClientID %>');

        rstTxtbox.value = result;
    }
</script>

Code

C#

protected void Save(object sender, EventArgs e)
{
    string total = txtvalue.Text;
    // Use the total variable to save in database.
    ScriptManager.RegisterStartupScript(this, this.GetType(), "alert", "alert('" + total + "');", true);
}

VB.Net

Protected Sub Save(ByVal sender As Object, ByVal e As EventArgs)
    Dim total As String = txtvalue.Text
    ScriptManager.RegisterStartupScript(Me, Me.GetType(), "alert", "alert('" & total & "');", True)
End Sub

Screenshot