Calculate and display value in ASP.Net TextBox using C# and VB.Net

Use below code.

HTML

<asp:TextBox ID="txt1" runat="server"></asp:TextBox>
<asp:TextBox ID="txt2" runat="server"></asp:TextBox>
<asp:Button Text="Calculate" runat="server" OnClick="Calculate" />
<asp:TextBox ID="txt3" runat="server"></asp:TextBox>

Code

C#

protected void Calculate(object sender, EventArgs e)
{
    txt3.Text = string.Format("{0:F6}", ((Convert.ToDouble(txt1.Text) * (80 / 100.00) * 12) / Convert.ToDouble(txt2.Text) / 100000.00));
}

VB.Net

Protected Sub Calculate(ByVal sender As Object, ByVal e As EventArgs)
    txt3.Text = String.Format("{0:F6}", ((Convert.ToDouble(txt1.Text) * (80 / 100.00) * 12) / Convert.ToDouble(txt2.Text) / 100000.00))
End Sub

Screenshot