Linq to sql 结合Linq to xml

最新推荐文章于 2025-07-26 13:11:15 发布

原创最新推荐文章于 2025-07-26 13:11:15 发布 · 110 阅读

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本文介绍如何使用C#和Visual Basic中的LINQ来查询和生成XML文件的方法。通过两个示例展示了从数据库中获取数据并将其转换为XML格式的过程。

//C#的例子

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;

namespace linq_part7_csharp
{
    public partial class _Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            NorthwindDataContext db = new NorthwindDataContext();
            //var q = from p in db.Products
            //        select new
            //        {
            //            Name = db.MyUpperFunction(p.ProductName)
            //        };

//GridView1.DataSource = q;
//GridView1.DataBind();

            XElement xml = new XElement("Products",
                                from c in db.Products
                                orderby c.ProductName
                                select new XElement("Produ",
                                          new XAttribute("id", c.ProductID),
                                          new XElement("产品名称", c.ProductName),
                                          new XElement("价格", c.UnitPrice))
                                );

            xml.Save(@"C:\xml.xml");
            System.Diagnostics.Process.Start(@"C:\xml.xml");

            // Loading from a file, you can also load from a stream
            //XDocument loaded = XDocument.Load(@"C:\xml.xml");
            //var q = from c in loaded.Descendants("contact")
            //        where (int)c.Attribute("contactId") < 4
            //        select (string)c.Element("firstName") + "" +
            //           (string)c.Element("lastName");

// foreach (string name in q)
// Console.WriteLine("Customer name = {0}", name);

}
}
}

//vb的例子，感觉更清晰和直观

Module Module1

Sub Main()

Dim db As New NorthwindDataContext

        'Dim customers = <customers>
        '                    <%= From customer In db.Customers _
        '                        Select <customer>
        '                                   <name><%= customer.CompanyName %></name>
        '                                   <phone><%= customer.Phone %></phone>
        '                                   <country><%= customer.Country %></country>
        '                               </customer> %>
        '                </customers>

        'Dim customers = <html>
        '                    <body>
        '                        <table width="100%" border="0">
        '                            <tr>
        '                                <td><b>Name</b></td>
        '                                <td><b>Phone</b></td>
        '                                <td><b>Country</b></td>
        '                            </tr>
        '                            <%= From customer In db.Customers _
        '                                Select <tr>
        '                                           <td><%= customer.CompanyName %></td>
        '                                           <td><%= customer.Phone %></td>
        '                                           <td><%= customer.Country %></td>
        '                                       </tr> %>
        '                        </table>
        '                    </body>
        '                </html>

'customers.Save("c:\customers.html")
'Process.Start("C:\customers.html")

        Dim orders = <orders>
                         <%= From customer In db.Customers _
                             Select <customer>
                                        <name><%= customer.CompanyName %></name>
                                        <phone><%= customer.Phone %></phone>
                                        <orders>
                                            <%= From order In customer.Orders _
                                                Select <order total=<%= Aggregate detail In order.Order_Details Into Sum(detail.UnitPrice * detail.Quantity) %>>
                                                           <date><%= order.OrderDate %></date>
                                                           <address><%= order.ShipAddress %></address>
                                                           <details>
                                                               <%= From detail In order.Order_Details _
                                                                   Select <item id=<%= detail.ProductID %>>
                                                                              <product><%= detail.Product.ProductName %></product>
                                                                          </item> %>
                                                           </details>
                                                       </order> %>
                                        </orders>
                                    </customer> %>
                     </orders>