在DataGrid中最后一行加上一个统计字段

Adding a Totals Field in a DataGrid (By Doug Seven )
Do you spend much time reading posts on the ASPNG lists? If not, I highly recommend it. You can sign-up at http://www.asp.net or http://www.asplists.com. Lately one of the questions that has been popping up a lot is, "How do I show column totals in a DataGrid?" Personally I have provided sample code for this question more than a few times, so I thought it would only be appropriate that we here at DotNetJunkies HQ get a tutorial up on the topic. In this tutorial you will learn how to programmatically sum the values of a column in a DataGrid, and display that total in the footer of the DataGrid. The downloadable sample code for this tutorial is in both C# and Visual Basic.NET.

The end result of this tutorial will look like this:

Lets Get It On

The DataGrid used in the screenshot above is a pretty typical DataGrid. There are a few properties that control the look and feel of the DataGrid, and it uses two BoundColumns to render the data, but that is it. The real important piece that makes this work is the use of the DataGrid.OnItemDataBound event. This event fires each time a record is bound to the DataGrid. You can create an event handler for this event, and manipulate the data in the record. In this case, you will keep a running total of the sum of the Price column.

The Footer row is the last row that is data bound. When this row is bound, in the event handler you will render the running total to the Price column. Sounds simple, huh?

Break It Down

First lets get that pesky Web form out of the way. For this tutorial you will use a Web Form (calcTotals.aspx) and a code behind class file (calcTotals.aspx.cs). For the purposes of this tutorial, the code behind class will be compiled using a Just-In-Time compiler. This is identified by the addition of the SRC attribute in the @ Page directive. Here is the code for calcTotals.aspx:

<%@ Page Inherits="myApp.calcTotals" Src="20010731T0101.aspx.cs" %>

<html>

<asp:DataGrid id="MyGrid" runat="server"

AutoGenerateColumns="False"

CellPadding="4" CellSpacing="0"

BorderStyle="Solid" BorderWidth="1"

Gridlines="None" BorderColor="Black"

ItemStyle-Font-Name="Verdana"

ItemStyle-Font-Size="9pt"

HeaderStyle-Font-Name="Verdana"

HeaderStyle-Font-Size="10pt"

HeaderStyle-Font-Bold="True"

HeaderStyle-ForeColor="White"

HeaderStyle-BackColor="Blue"

FooterStyle-Font-Name="Verdana"

FooterStyle-Font-Size="10pt"

FooterStyle-Font-Bold="True"

FooterStyle-ForeColor="White"

FooterStyle-BackColor="Blue"

OnItemDataBound="MyDataGrid_ItemDataBound"

ShowFooter="True">

<asp:BoundColumn HeaderText="Title" DataField="title" />

<asp:BoundColumn HeaderText="Price" DataField="price"

ItemStyle-HorizontalAlign="Right"

HeaderStyle-HorizontalAlign="Center" />

</Columns>

</asp:DataGrid>

</body>

</html>

In the Web Form you use the @ Page directive to declare the code behind class that this page inherits from. The SRC attribute indicates that the code behind class will be compiled on the fly using the JIT compiler. The bulk of the rest of the code in the Web Form is style declarations to make the DataGrid look good, after all, image is everything.

One of the last properties specified is the OnItemDataBound property. This specifies what event handler should fire when the OnItemDataBound event occurs.

The DataGrid (MyGrid) in the Web Form has two BoundColumns, one for Title and one for Price. This is where you will display the title and price columns from the Titles table in the Pubs database (SQL Server).

Ignore the Code Behind the Curtain

The code behind class is where all the work will be done. In the code behind class you will handle two events, the Page_Load event, and the MyGrid_OnItemDataBound event, and have one private method, CalcTotal, which will simply do the math to maintain the running total.

Start by building the basic structure for the code behind class.

using System;

using System.Web;

using System.Web.UI;

using System.Web.UI.WebControls;

using System.Web.UI.HtmlControls;

using System.Data;

using System.Data.SqlClient;

namespace myApp

{

public class calcTotals : Page

{

protected DataGrid MyGrid;

private double runningTotal = 0;

}

In the basic structure of the code behind class you import the necessary namespaces with the using statement. Inside the class declaration you declare two variables, one for the DataGrid (MyGrid) which maps the variable in the code behind class to the control in the Web Form; and a double that will be used to maintain the running total of the Price column of the DataGrid.

The Page_Load Event Handler

In the Page_Load event handler all you do is make a connection to your SQL Server database and execute a simply SqlCommand. You are retrieving the title and price data for all titles that have a price greater than zero. You use the SqlCommand.ExecuteReader method to return a SqlDataReader and bind that directly to the DataGrid (MyGrid).

protected void Page_Load(object sender, EventArgs e)

{

SqlConnection myConnection = new SqlConnection("server=Localhost;database=pubs;uid=sa;pwd=;");

SqlCommand myCommand = new SqlCommand("SELECT title, price FROM Titles WHERE price > 0", myConnection);

try

{

myConnection.Open();

MyGrid.DataSource = myCommand.ExecuteReader();

MyGrid.DataBind();

myConnection.Close();

}

catch(Exception ex)

{

//An error occured

HttpContext.Current.Response.Write(ex.ToString());

}

The CalcTotals Method

The CalcTotals method adds the passed in value to the runningTotal variable. The value will be passed in as a string value. You will need to parse it as a double, since the runningTotal variable is a double type.

private void CalcTotal(string _price)

{

try

{

runningTotal += Double.Parse(_price);

}

catch

{

//A value was null

}

The MyGrid_ItemDataBound Event

The MyGrid_ItemDataBound event is called as each row in the data source is bound to the DataGrid. In this event handler you can work with the data in each row, in the form of a DataGridItem. For you purpose here, you will need to call CalcTotals and pass in the text from the Price column, and then format the Price column as currency for each row (Item or AlternatingItem), and display the value of runningTotal in the Footer row.

public void MyDataGrid_ItemDataBound(object sender, DataGridItemEventArgs e)

{

if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)

{

CalcTotal( e.Item.Cells[1].Text );

e.Item.Cells[1].Text = string.Format("{0:c}", Convert.ToDouble(e.Item.Cells[1].Text));

}

else if(e.Item.ItemType == ListItemType.Footer )

{

e.Item.Cells[0].Text="Total";

e.Item.Cells[1].Text = string.Format("{0:c}", runningTotal);

}

In the MyGrid_ItemDataBound event handler, first you evaluate to see if the current DataGridItem is an Item or AlternatingItem row, using the ListItemType enumerator. If it is, you call CalcTotals and pass in the value of the Price column as the argument. Next you apply formatting to the Price column to render it as currency.

If the DataGridItem is a Footer, you display the runningTotal, formatted as currency.

Summary

In this tutorial you learned how to use the DataGrid.OnItemDataBound event to maintain a running total of a DataGrid column. Using this event you were able to create a total sum of the column and render it to the footer row of the DataGrid.

上面是来自http://www.dotnetjunkies.com网上
其实要想在末尾最后一行加上一个统计字段并不难
主要是加上
MyDataGrid_ItemDataBound事件
然后是
if(e.Item.ItemType == ListItemType.Footer )
{
    double a;                        vb.net中使用dim a as double
    //在这里填充dataset
    for(i=0;i<dataset.table[0].rows.count-1;i++)         //vb.net中使用 for i=0 to dataset.table[0].rows.count-1
    a+=double.parse(dataset.table[0].rows[i].columun["字段名"]);.//vb.net中使用val(dataset.table(0).rows(i).columun("字段名"))
    e.Item.Cells[0].Text="Total";//这里的cell是列的意思
    e.Item.Cells[1].Text = a
}
其他行的绑定可以在page_load里面写,或写成一个函数调用,没有必要都写到这个里面
再加上
if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
{
     //绑定
}
判断

posted on 2005-05-02 19:02 kasafuma 阅读(892) 评论(0) 收藏举报