C# 上传大文件

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上传大文件首先要修改web.config文件，否则上传报错。在web.config添加如下配置maxRequestLength表示能上传的最大文件值，单位是KB，requestLengthDiskThreshold表示超过多少KB之后的文件缓存到文件系统，不缓存在内存，以减轻内存负担。requestLengthDiskThreshold必须小于maxRequestLength

上传页面

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebFormLargeFile.aspx.cs" Inherits="WebApplication1.WebFormLargeFile" %><!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></title>
<style type ="text/css" >
.fileList
{
margin-bottom :5px;
}
</style>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:Label ID ="lblFile" runat ="server" AssociatedControlID ="upFile" Text ="World Document："></asp:Label>
<asp:FileUpload ID ="upFile" runat ="server" /> 
<asp:Button ID ="btnAdd" runat ="server" onclick="btnAdd_Click" Text ="上传" />
<hr />
<asp:Repeater ID ="rptFiles" runat ="server" DataSourceID ="srcFiles" >
<HeaderTemplate >
<ul class ="fileList">
</HeaderTemplate>
<ItemTemplate >
<li>
<asp:HyperLink ID ="lnkFile" runat ="server" Text ='<%#Eval("FileName") %>' NavigateUrl ='<%#Eval("Id","~/FileHandlerLarge.ashx?Id={0}") %>'></asp:HyperLink>
</li>
</ItemTemplate>
<FooterTemplate >
</ul>
</FooterTemplate>
</asp:Repeater>
</div>
<asp:SqlDataSource ID="srcFiles" runat="server"
ConnectionString="Data Source=localhost;Initial Catalog=test;Integrated Security=True" ProviderName ="System.Data.SqlClient"
SelectCommand="SELECT * FROM [Files]"></asp:SqlDataSource>
</form>
</body>
</html>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.IO;
using System.Data.SqlClient;
using System.Data;namespace WebApplication1
{
public partial class WebFormLargeFile : System.Web.UI.Page
{
const string connStr = "Data Source=localhost;Initial Catalog=test;Integrated Security=True";
protected void Page_Load(object sender, EventArgs e)
{ } protected void btnAdd_Click(object sender, EventArgs e)
{
if (upFile.HasFile)
{
if (CheckFileType(upFile.FileName))
{
AddFile(upFile.FileName, upFile.FileContent);
rptFiles.DataBind();
}
}
} private bool CheckFileType(string fileName)
{
return Path.GetExtension(fileName).ToLower() == ".doc";
} private void AddFile(string fileName,Stream upload)
{
using(SqlConnection conn=new SqlConnection(connStr))
{
string sql = "insert into Files (FileName) values(@FileName)\n select @Id=SCOPE_IDENTITY() ";
SqlCommand cmd = new SqlCommand(sql,conn);
cmd.Parameters.AddWithValue("@FileName", fileName);
SqlParameter IdParam= new SqlParameter("@Id", SqlDbType.Int);
IdParam.Direction = ParameterDirection.Output;
cmd.Parameters.Add(IdParam); conn.Open();
cmd.ExecuteNonQuery();
int id =Convert.ToInt32(IdParam.Value);
StoreFile(id, conn, upload);
} } private void StoreFile(int Id, SqlConnection conn, Stream upload)
{
int bufferLength = ;
BinaryReader reader = new BinaryReader(upload);//从流中读取字节数据
byte[] chuk = new byte[bufferLength];
chuk = reader.ReadBytes(bufferLength); SqlCommand cmd =new SqlCommand("update Files set FileBytes=@FileBytes where Id =@id",conn);
cmd.Parameters.AddWithValue("@id", Id);
cmd.Parameters.Add("@FileBytes", SqlDbType.VarBinary, bufferLength).Value = chuk;
cmd.ExecuteNonQuery(); //set 列名.write(表达式,@offset,@length)用表达式的值替换某列从开始索引@length长度字符
//set 列名.write(表达式,null,0)在某列末尾追加
//set 列名.write(表达式,0,null)从开始位置替换
//set 列名.write(null,@offset,@length)可以用来删除数据
//set 列名.write(表达式,@offset,@length)只能用于SQL Server2005以上
//set 列名.write(表达式,@offset,@length)用法参考https://www.debugease.com/mssqlbasic/1274092.html
SqlCommand cmdAppend = new SqlCommand("update Files set FileBytes.Write(@FileBytes,null,0) where Id =@id", conn);
cmdAppend.Parameters.AddWithValue("@id", Id);
cmdAppend.Parameters.Add("FileBytes", SqlDbType.VarBinary, bufferLength);
chuk = reader.ReadBytes(bufferLength);
while (chuk.Length > )
{
cmdAppend.Parameters["FileBytes"].Value = chuk;
cmdAppend.ExecuteNonQuery();
chuk = reader.ReadBytes(bufferLength);
}
reader.Close();
}
}
}

文件处理页面

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Data.SqlClient;
using System.Data;namespace WebApplication1
{
/// <summary>
/// FileHandlerLarge 的摘要说明
/// </summary>
public class FileHandlerLarge : IHttpHandler
{
const string connStr = "Data Source=localhost;Initial Catalog=test;Integrated Security=True";
public void ProcessRequest(HttpContext context)
{
context.Response.ContentType = "application/msword";
context.Response.Buffer = false;
SqlConnection conn = new SqlConnection(connStr);
SqlCommand cmd = new SqlCommand("select FileBytes from Files where Id =@Id", conn);
cmd.Parameters.AddWithValue("@Id", context.Request["Id"]);
using (conn)
{
conn.Open();
SqlDataReader reader = cmd.ExecuteReader(CommandBehavior.SequentialAccess);
if (reader.Read())
{
int bufferSize = ;
byte[] chunk = new byte[bufferSize];
long retCount = ;
long startIndex = ;
//public override long GetBytes(int i, long dataIndex, byte[] buffer, int bufferIndex, int length)
//从指定的列偏移量将字节流读入缓冲区，并将其作为从给定的缓冲区偏移量开始的数组。
retCount = reader.GetBytes(, startIndex, chunk, , bufferSize); while (retCount == bufferSize)
{
context.Response.BinaryWrite(chunk);
startIndex += bufferSize;
retCount = reader.GetBytes(, startIndex, chunk, , bufferSize); } //写入最后一个字节数组
byte[] actualChunk = new byte[retCount - ];
Buffer.BlockCopy(chunk, , actualChunk, , (int)retCount - );
context.Response.BinaryWrite(actualChunk);
}
}
context.Response.Write("Hello World");
} public bool IsReusable
{
get
{
return false;
}
}
}
}