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

<configuration>
<system.web>    
<httpRuntime maxRequestLength ="1048576" requestLengthDiskThreshold ="100"/>
</system.web>
</configuration>

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"  />&nbsp;
        <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>

View Code

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 = 8040;
            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 > 0)
            {
                cmdAppend.Parameters["FileBytes"].Value = chuk;
                cmdAppend.ExecuteNonQuery();
                chuk = reader.ReadBytes(bufferLength);
            }
            reader.Close();
        }
    }
}

View Code

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 = 8040;
                    byte[] chunk = new byte[bufferSize];
                    long retCount = 0;
                    long startIndex = 0;
                    //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(0, startIndex, chunk, 0, bufferSize);
                    
                    while (retCount == bufferSize)
                    {
                        context.Response.BinaryWrite(chunk);
                        startIndex += bufferSize;
                        retCount = reader.GetBytes(0, startIndex, chunk, 0, bufferSize);

                    }

                    //写入最后一个字节数组
                    byte[] actualChunk = new byte[retCount - 1];
                    Buffer.BlockCopy(chunk, 0, actualChunk, 0, (int)retCount - 1);
                    context.Response.BinaryWrite(actualChunk);
                }
            }
            context.Response.Write("Hello World");
        }

        public bool IsReusable
        {
            get
            {
                return false;
            }
        }
    }
}