http://blog.youkuaiyun.com/net_lover/archive/2008/01/27/2068933.aspx
LINQ是Visual Studio 2008及其以后版本中提供的功能，将强大的查询扩展到C#和VB.NET语言语法之中。LINQ提供了标准、简单的模式来查询和更新数据，同时还允许程序开发人员进行扩展，支持任何类型的数据存储。Visual Studio 2008包含了LINQ提供者程序集，能够对.NET Framework集合，内存中的对象数组，SQL Server数据库，ADO.NET Dataset和XML文档进行语言集成的查询。另外，我们也可以自己编写LINQ提供者，提供对任何类型数据的查询，只要实现了IEnumerable或者IEnumerable<T> (C#)或 IEnumerable (Of T) (Visual Basic)的数据类型，都可以进行使用LINQ进行操作。我们可以使用完全相同的语法查询SQL数据库、XML文档、ADO.NET的Dataset（DataTable）、内存中的集合对象，以及任何支持LINQ的远程或者本地数据源。在LINQ查询中，只与对象打交道，因此，可以完全不需要知道数据存储的数据源，而且采用的编程模型和语法也完全相同。
所有的LINQ查询基本上都是由3个基本的操作组成：得到数据源，创建查询和执行查询3个过程。数据的获得是在执行查询的时候完成的。在上一部分的例子（http://blog.youkuaiyun.com/net_lover/archive/2008/01/23/2060425.aspx）中，
NorthWindDataContext NorthWind = new NorthWindDataContext();
是得到数据源
var query = from c in NorthWind.Customers where c.Country == "USA" select new { c.Country, c.CompanyName };
是创建查询，此时并没有对数据执行任何操作，
GridView2.DataSource = query;
GridView2.DataBind();
在数据绑定时，才真正得到数据。
但是，有的查询需要立即执行，将结果放在内存中，可以调用查询或者查询变量的ToList<(Of <TSource>)> 或者 ToArray<(Of <TSource>)>方法。例如：
var query2 = from c in NorthWind.Customers where c.Country == "USA" select new { c.Country, c.CompanyName };
var query3 = query2.ToList();
好，既然说LINQ可以查询任何类型的数据，下面，咱们就试试如何查询一个Excel文件（说明：本程序在Excel 2003下今天测试的，在Excel2007中可能更简单，不过没有测试。运行本程序可能需要采用模拟或者调整Excel.exe的权限，另外注意：使用之前需要引用COM：Microsoft Office 11.0 Object Library
如果引用列表中没有，需要自行添加 C:/Program Files/Microsoft Office/OFFICE11/EXCEL.EXE）。
1，先准备一个Book1.xls，文件内容如下（将下面的XML文件在Excel里打开，另存为Book1.xls即可）：
<?xml version="1.0"?>
<?mso-application progid="Excel.Sheet"?>
<Workbook xmlns="urn:schemas-microsoft-com:office:spreadsheet"
xmlns:o="urn:schemas-microsoft-com:office:office"
xmlns:x="urn:schemas-microsoft-com:office:excel"
xmlns:ss="urn:schemas-microsoft-com:office:spreadsheet"
xmlns:html="http://www.w3.org/TR/REC-html40">
<DocumentProperties xmlns="urn:schemas-microsoft-com:office:office">
<Author>zhy</Author>
<LastAuthor>zhy</LastAuthor>
<Created>2008-01-25T13:13:34Z</Created>
<LastSaved>2008-01-26T13:10:56Z</LastSaved>
<Version>11.9999</Version>
</DocumentProperties>
<ExcelWorkbook xmlns="urn:schemas-microsoft-com:office:excel">
<WindowHeight>13050</WindowHeight>
<WindowWidth>16020</WindowWidth>
<WindowTopX>0</WindowTopX>
<WindowTopY>105</WindowTopY>
<ProtectStructure>False</ProtectStructure>
<ProtectWindows>False</ProtectWindows>
</ExcelWorkbook>
<Styles>
<Style ss:ID="Default" ss:Name="Normal">
<Alignment ss:Vertical="Center"/>
<Borders/>
<Font ss:FontName="宋体" x:CharSet="134" ss:Size="12"/>
<Interior/>
<NumberFormat/>
<Protection/>
</Style>
</Styles>
<Worksheet ss:Name="Sheet1">
<Table ss:ExpandedColumnCount="5" ss:ExpandedRowCount="21" x:FullColumns="1"
x:FullRows="1" ss:DefaultColumnWidth="54" ss:DefaultRowHeight="14.25">
<Column ss:Index="3" ss:AutoFitWidth="0" ss:Width="102"/>
<Column ss:AutoFitWidth="0" ss:Width="263.25"/>
<Column ss:AutoFitWidth="0" ss:Width="246.75"/>
<Row ss:Index="2">
<Cell ss:Index="2"><Data ss:Type="String">Category</Data></Cell>
<Cell><Data ss:Type="String">CategoryID</Data></Cell>
<Cell><Data ss:Type="String">CategoryName</Data></Cell>
</Row>
<Row>
<Cell ss:Index="3"><Data ss:Type="Number">1</Data></Cell>
<Cell><Data ss:Type="String">ASP.NET</Data></Cell>
</Row>
<Row>
<Cell ss:Index="3"><Data ss:Type="Number">8</Data></Cell>
<Cell><Data ss:Type="String">VB.NET</Data></Cell>
</Row>
<Row>
<Cell ss:Index="3"><Data ss:Type="Number">9</Data></Cell>
<Cell><Data ss:Type="String">Visual C#</Data></Cell>
</Row>
<Row>
<Cell ss:Index="3"><Data ss:Type="Number">11</Data></Cell>
<Cell><Data ss:Type="String">XML/XSL</Data></Cell>
</Row>
<Row>
<Cell ss:Index="3"><Data ss:Type="Number">6</Data></Cell>
<Cell><Data ss:Type="String">Web Services</Data></Cell>
</Row>
<Row>
<Cell ss:Index="3"><Data ss:Type="Number">12</Data></Cell>
<Cell><Data ss:Type="String">.NET FAQs</Data></Cell>
</Row>
<Row ss:Index="16">
<Cell ss:Index="2"><Data ss:Type="String">Article</Data></Cell>
<Cell><Data ss:Type="String">CategoryID</Data></Cell>
<Cell><Data ss:Type="String">Title</Data></Cell>
<Cell><Data ss:Type="String">Guid</Data></Cell>
</Row>
<Row>
<Cell ss:Index="3"><Data ss:Type="Number">1</Data></Cell>
<Cell><Data ss:Type="String">ASP.NET2.0中将文件上传到数据库 </Data></Cell>
<Cell><Data ss:Type="String">17612afb-3fc0-4fb9-bfa9-00cba28336e9</Data></Cell>
</Row>
<Row>
<Cell ss:Index="3"><Data ss:Type="Number">1</Data></Cell>
<Cell><Data ss:Type="String">不经保存，直接读取上传文件的内容 </Data></Cell>
<Cell><Data ss:Type="String">78280914-a75c-40dc-9dac-322b3d81be35</Data></Cell>
</Row>
<Row>
<Cell ss:Index="3"><Data ss:Type="Number">1</Data></Cell>
<Cell><Data ss:Type="String">一次编辑 GridView 的所有行 </Data></Cell>
<Cell><Data ss:Type="String">a933b187-06c3-4263-9eec-414a54d9c815</Data></Cell>
</Row>
<Row>
<Cell ss:Index="3"><Data ss:Type="Number">11</Data></Cell>
<Cell><Data ss:Type="String">创建、查询、修改带名称空间的 XML 文件的例子</Data></Cell>
<Cell><Data ss:Type="String">7b4c7a42-4cdf-40d1-b293-e86da109a34c</Data></Cell>
</Row>
<Row>
<Cell ss:Index="3"><Data ss:Type="Number">11</Data></Cell>
<Cell><Data ss:Type="String">用XSL把XML的数据转换成完美的多列表格形式</Data></Cell>
<Cell><Data ss:Type="String">yawo3qgm-xd53-4d3d-oybr-blsbx5bngaym</Data></Cell>
</Row>
</Table>
<WorksheetOptions xmlns="urn:schemas-microsoft-com:office:excel">
<Print>
<ValidPrinterInfo/>
<PaperSizeIndex>9</PaperSizeIndex>
<HorizontalResolution>200</HorizontalResolution>
<VerticalResolution>200</VerticalResolution>
</Print>
<Selected/>
<Panes>
<Pane>
<Number>3</Number>
<ActiveRow>6</ActiveRow>
<ActiveCol>2</ActiveCol>
</Pane>
</Panes>
<ProtectObjects>False</ProtectObjects>
<ProtectScenarios>False</ProtectScenarios>
</WorksheetOptions>
</Worksheet>
<Worksheet ss:Name="Sheet2">
<Table ss:ExpandedColumnCount="0" ss:ExpandedRowCount="0" x:FullColumns="1"
x:FullRows="1" ss:DefaultColumnWidth="54" ss:DefaultRowHeight="14.25"/>
<WorksheetOptions xmlns="urn:schemas-microsoft-com:office:excel">
<ProtectObjects>False</ProtectObjects>
<ProtectScenarios>False</ProtectScenarios>
</WorksheetOptions>
</Worksheet>
<Worksheet ss:Name="Sheet3">
<Table ss:ExpandedColumnCount="0" ss:ExpandedRowCount="0" x:FullColumns="1"
x:FullRows="1" ss:DefaultColumnWidth="54" ss:DefaultRowHeight="14.25"/>
<WorksheetOptions xmlns="urn:schemas-microsoft-com:office:excel">
<ProtectObjects>False</ProtectObjects>
<ProtectScenarios>False</ProtectScenarios>
</WorksheetOptions>
</Worksheet>
</Workbook>
2，创建aspx：
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="LinqExcel.aspx.cs" Debug="true"
Inherits="LinqExcel" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>LINQ to Excel</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false" CellPadding="4">
<Columns>
<asp:HyperLinkField DataNavigateUrlFields="CategoryID" Target="_blank"
DataNavigateUrlFormatString="http://dotnet.aspx.cc/ShowList.aspx?id={0}"
HeaderText="栏目" DataTextField="CategoryName" DataTextFormatString="【{0}】" />
<asp:HyperLinkField DataNavigateUrlFields="ArticleGuid" Target="_blank"
DataNavigateUrlFormatString="http://dotnet.aspx.cc/article/{0}/read.aspx"
HeaderText="文章标题" DataTextField="ArticleTitle" />
</Columns>
</asp:GridView>
</div>
</form>
</body>
</html>
3，编写代码文件：
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;
using System.Collections.Generic;
using Microsoft.Office.Interop.Excel;
public partial class LinqExcel : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
string f = Server.MapPath("~/App_Data/Book1.xls");
Open(f);
}
public void Open(string FilePath)
{
m_objExcel = new Application();
m_objExcel.Visible = false;
m_objExcel.DisplayAlerts = false;
if (m_objExcel.Version != "11.0")
{
Response.Write("您的 Excel 版本不是 11.0 （Office 2003），操作可能会出现问题。");
m_objExcel.Quit();
return;
}
m_objBooks = (Workbooks)m_objExcel.Workbooks;
m_objBook = m_objBooks.Open(FilePath, m_objOpt, m_objOpt, m_objOpt, m_objOpt, m_objOpt, m_objOpt, m_objOpt, m_objOpt, m_objOpt, m_objOpt, m_objOpt, m_objOpt, m_objOpt, m_objOpt);
m_objSheets = (Sheets)m_objBook.Worksheets;
m_objSheet = (_Worksheet)(m_objSheets.get_Item(1));
List<Category> categorylist = LoadCategory();
List<Article> articlelist = LoadArticle();
var query = from art in articlelist
join cat in categorylist on art.CategoryID equals cat.CategoryID
select new { art.ArticleTitle, art.CategoryID, art.ArticleGuid, cat.CategoryName };
GridView1.DataSource = query;
GridView1.DataBind();
this.Close();
this.Dispose2();
}
private void Close()
{
m_objBook.Close(false, m_objOpt, m_objOpt);
m_objExcel.Quit();
}
public void Dispose2()
{
ReleaseObj(m_objSheets);
ReleaseObj(m_objBook);
ReleaseObj(m_objBooks);
ReleaseObj(m_objExcel);
System.GC.Collect();
System.GC.WaitForPendingFinalizers();
}
private void ReleaseObj(object o)
{
try
{
System.Runtime.InteropServices.Marshal.ReleaseComObject(o);
}
catch { }
finally { o = null; }
}
private List<Category> LoadCategory()
{
List<Category> lc = new List<Category>();
Category c;
m_objRange = m_objSheet.get_Range("C2", "D8");
for (int i = 1; i < m_objRange.Rows.Count; i++)
{
c = new Category();
Range r = (Range)m_objRange.Cells[i + 1, 1];
c.CategoryID = Convert.ToInt32(r.Value2);
r = (Range)m_objRange.Cells[i + 1, 2];
c.CategoryName = Convert.ToString(r.Value2);
lc.Add(c);
}
return lc;
}
private List<Article> LoadArticle()
{
List<Article> al = new List<Article>();
Article a;
m_objRange = m_objSheet.get_Range("C16", "E21");
for (int i = 1; i < m_objRange.Rows.Count; i++)
{
a = new Article();
Range r = (Range)m_objRange.Cells[i + 1, 1];
a.CategoryID = Convert.ToInt32(r.Value2);
r = (Range)m_objRange.Cells[i + 1, 2];
a.ArticleTitle = Convert.ToString(r.Value2);
r = (Range)m_objRange.Cells[i + 1, 3];
a.ArticleGuid = Convert.ToString(r.Value2);
al.Add(a);
}
return al;
}
private Application m_objExcel = null;
private Workbooks m_objBooks = null;
private _Workbook m_objBook = null;
private Sheets m_objSheets = null;
private _Worksheet m_objSheet = null;
private Range m_objRange = null;
private object m_objOpt = System.Reflection.Missing.Value;
}
public class Category
{
public Int32 CategoryID;
public string CategoryName;
}
public class Article
{
public Int32 CategoryID;
public string ArticleTitle;
public string ArticleGuid;
}
上面的代码将Excel中的两个区域分别放到了两个对象里面，利用对象进行LINQ查询。当然，这里的例子只是说明技术，在实际的应用中需要进行进一步的封装，也可能换别的方法。
4，运行结果：
由于LINQ可以自己定义提供者，因此，我们可以定义自己的数据源提供者。下面是网上写的一个LINQ to Excel Provider （作者是：http://solidcoding.blogspot.com/2007/12/linq-to-excel-provider.html）。其代码和使用方法如下：
LinqExcelProvider.cs：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.OleDb;
/// <summary>
/// Summary description for LinqExcelProvider
/// </summary>
public class ExcelRow
{
List<object> columns;
public ExcelRow()
{
columns = new List<object>();
}
internal void AddColumn(object value)
{
columns.Add(value);
}
public object this[int index]
{
get { return columns[index]; }
}
public string GetString(int index)
{
if (columns[index] is DBNull)
{
return null;
}
return columns[index].ToString();
}
public int Count
{
get { return this.columns.Count; }
}
}
public class ExcelProvider : IEnumerable<ExcelRow>
{
private string sheet;
private string filePath;
private List<ExcelRow> rows;
public ExcelProvider()
{
rows = new List<ExcelRow>();
}
public static ExcelProvider Create(string filePath, string sheet)
{
ExcelProvider provider = new ExcelProvider();
provider.sheet = sheet;
provider.filePath = filePath;
return provider;
}
private void Load()
{
string connectionString = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source={0};Extended Properties=""Excel 8.0;HDR=YES;""";
connectionString = string.Format(connectionString, filePath);
rows.Clear();
using (OleDbConnection conn = new OleDbConnection(connectionString))
{
conn.Open();
using (OleDbCommand cmd = conn.CreateCommand())
{
cmd.CommandText = "select * from [" + sheet + "$]";
using (OleDbDataReader reader = cmd.ExecuteReader())
{
while (reader.Read())
{
ExcelRow newRow = new ExcelRow();
for (int count = 0; count < reader.FieldCount; count++)
{
newRow.AddColumn(reader[count]);
}
rows.Add(newRow);
}
}
}
}
}
public IEnumerator<ExcelRow> GetEnumerator()
{
Load();
return rows.GetEnumerator();
}
System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
{
Load();
return rows.GetEnumerator();
}
}
使用方法：
ExcelProvider provider = ExcelProvider.Create(Server.MapPath("~/App_Data/Book2.xls"), "Sheet1");
foreach (ExcelRow row in (from x in provider select x))
{
Response.Write("<li>" + row.GetString(0) + " " + row.GetString(1));
}
这样，查询数据就很方便了。
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