Getting total values of a certain column from GridView

Question

Him

I am using a ASP.NET/VB.NET with SQL-Server-2012.

I have a a GridView column with 3 fields and 1 template field as shown below:

<asp:GridView ID="grdItems" runat="server" AutoGenerateColumns="False" CellPadding="4" DataSourceID="SqlDataSource3" Font-Names="Tahoma" ForeColor="#333333" GridLines="None">
    <AlternatingRowStyle BackColor="White" ForeColor="#284775" />
    <Columns>
        <asp:BoundField DataField="item_name" HeaderText="Item" SortExpression="item_name" />
        <asp:BoundField DataField="item_cost" HeaderText="Cost (inc. VAT)" SortExpression="item_cost" />
        <asp:BoundField DataField="item_quantity" HeaderText="Quantity" SortExpression="item_quantity" />
        <asp:TemplateField HeaderText="Sub-Total (inc. VAT)">
            <ItemTemplate>
                <asp:Label ID="TextBox3" runat="server" Text='<%# Convert.ToInt32(Eval("item_quantity")) * Convert.ToDouble(Eval("item_cost"))%>'></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField>
            <FooterTemplate>
                <asp:Label ID="lblTotalPrice" runat="server" />
            </FooterTemplate>                  
        </asp:TemplateField>
    </Columns>
    <EditRowStyle BackColor="#999999" />
    <FooterStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
    <HeaderStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" HorizontalAlign="Center" VerticalAlign="Middle" />
    <PagerStyle BackColor="#284775" ForeColor="White" HorizontalAlign="Center" />
    <RowStyle BackColor="#F7F6F3" ForeColor="#333333" HorizontalAlign="Center" VerticalAlign="Middle" />
    <SelectedRowStyle BackColor="#E2DED6" Font-Bold="True" ForeColor="#333333" />
    <SortedAscendingCellStyle BackColor="#E9E7E2" />
    <SortedAscendingHeaderStyle BackColor="#506C8C" />
    <SortedDescendingCellStyle BackColor="#FFFDF8" />
    <SortedDescendingHeaderStyle BackColor="#6F8DAE" />
</asp:GridView>

Code behind:

Imports System.Data.SqlClient
Imports System.Data

Partial Class ProjectReport
    Inherits System.Web.UI.Page

    Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load

        Dim ProjectID = Session("project_id")
        Session("ProjectID") = ProjectID

    End Sub
    Protected Sub grdItems_RowDataBound(sender As Object, e As GridViewRowEventArgs)

        Dim totalPrice As Decimal = 0

        If e.Row.RowType = DataControlRowType.DataRow Then


            Dim lblPrice As Label = DirectCast(e.Row.FindControl("lblTotalPrice"), Label)

            Dim price As Decimal = [Decimal].Parse(lblPrice.Text)


            totalPrice += price

        End If

        If e.Row.RowType = DataControlRowType.Footer Then
            Dim lblTotalPrice As Label = DirectCast(e.Row.FindControl("lblTotalPrice"), Label)

            lblTotalPrice.Text = totalPrice.ToString()


        End If
    End Sub


End Class

DataBound()

   Private Sub BindData()

        Dim conn As New SqlConnection("Data Source=BRIAN-PC\SQLEXPRESS;Initial Catalog=master_db;Integrated Security=True")
        Dim query As New SqlCommand("SELECT Items.item_name, Items.item_cost, project_items.item_quantity FROM Items INNER JOIN project_items ON items.item_id = project_items.item_id WHERE project_items.project_id = @parameter", conn)

        query.Parameters.AddWithValue("@UserID", Session("ProjectID"))

        Dim da As New SqlDataAdapter(query, conn)

        da.SelectCommand = query

        Dim table As New DataTable()




        da.Fill(table)

        grdItems.DataSource = table
        grdItems.DataBind()
    End Sub

The last column (the template field) multiplies the quantity field with the cost field.

How do I calculate all the values (by adding) in the template field?

Solution

You must use the databinding events to sum the values. See this example and adapt to your needs:

private Decimal OrderTotal;

protected void GridView1_DataBinding(object sender, EventArgs e)
{ 
    OrderTotal = 0.0M;
}

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        //Keep adding the subtotal here
        OrderTotal += Subtotal;               
    }
}

protected void GridView1_DataBound(object sender, EventArgs e)
{      
    //Set a control with the total sum
    LabelOrderTotal.Text = OrderTotal.ToString("C");
}

Basically you keep adding the values in the RowDataBound event and in the DataBound event you set a label with the total sum. Alternatively, you can iterate over your grid in the DataBound event and add everything up.

Comments

[Brian]

Hi, I have follows the tutorial to no avail. I will update new code. Thanks.

[nmat]

@Brian You're missing the DataBound event. Read the example carefully

[Brian]

Please see updated code. I'm getting an error in 'query' telling me that an SqlCommand cannot be converted to string