c# - How to add a calculated column to a DataTable

Add an expression column to a DataTable
ExpressionColumn.aspx

<%@ Page Language="C#" AutoEventWireup="true" %>
<%@ Import Namespace="System.Data" %>

<!DOCTYPE html>
<script runat="server">
    void Button1_Click(object sender, System.EventArgs e)
    {
        DataTable dt = new DataTable();

        DataColumn dc = new DataColumn();
        dc.ColumnName = "ProductName";
        dc.DataType = typeof(string);
        dt.Columns.Add(dc);

        DataColumn dc2 = new DataColumn();
        dc2.ColumnName = "ProductPrice";
        dc2.DataType = typeof(int);
        dt.Columns.Add(dc2);

        DataColumn dc3 = new DataColumn();
        dc3.ColumnName = "ProductVat";
        dc3.DataType = typeof(int);
        dt.Columns.Add(dc3);

        dt.Columns.Add(new DataColumn("TotalPrice", typeof(int), "ProductPrice + ProductVat"));

        dt.Rows.Add(new object[] { "asp.net example ebooks", 30, 1 });
        dt.Rows.Add(new object[] { "ado.net example ebooks", 35, 2 });
        dt.Rows.Add(new object[] { "ajax example ebooks", 40, 3 });
        GridView1.DataSource = dt;
        GridView1.DataBind();
    }
</script>

<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
    <title>DataColumn - How to add a calculated column (expression column) to a DataTable in ado.net</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <h2 style="color:DarkBlue; font-style:italic;">
            ADO.NET DataColumn - How to add a calculated column
            <br /> (expression column) to a DataTable in ado.net
        </h2>
        <hr width="425" align="left" color="CornFlowerBlue" />
        <asp:GridView 
            ID="GridView1"
            runat="server"
            BorderColor="CornflowerBlue"
            HeaderStyle-BackColor="DarkBlue"
            ForeColor="Snow"
            Width="500"
            >
            <RowStyle BackColor="AliceBlue" ForeColor="DodgerBlue" />
        </asp:GridView>
        <br />
        <asp:Button 
            ID="Button1"
            runat="server"
            OnClick="Button1_Click"
            Text="Populate GridView with expression column"
            Height="45"
            Font-Bold="true"
            ForeColor="DarkBlue"
            />
    </div>
    </form>
</body>
</html>
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