多线程从数据库二进制字段转成文件

旧系统的文件是以二进制保存在数据库字段中。

做系统切换时要把这些文件转换成文件

用到委托的多线程，这个以前也写过，这次写的时候又查了好久，

放在这标记一下。

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;
using System.Threading;

namespace LZDataExport
{
    public partial class CreateFile : Form
    {
        private DataTable dtLZ_KJ_CollectFile = null;
        DbHelperSQL LZdbHelper = null;
        string CurrentPath = "";
        MyDeleGateBytesToFile[] myDeleGates = null;
        IAsyncResult[] results = null;
        DateTime dtS = DateTime.Now;
        int ThreadNum = 10;
        int CompleteNum = 10;
        private Object thisLock = new Object();
        private DataTable dtAllFsFileId = null;
        public CreateFile()
        {
            InitializeComponent();
            //不设置的话线程回调时会提示:  线程间操作无效: 从不是创建控件的线程访问它。
            Control.CheckForIllegalCrossThreadCalls = false;
        }

        private void Start_Click(object sender, EventArgs e)
        {
            Start.Text = "处理中。。";
            Start.Enabled = false;
            dtAllFsFileId = new DbHelperSQL("JHDB_KJ").Query("select * from CollectFile_KJ").Tables[0];
            //理正数据库
            LZdbHelper = new DbHelperSQL("LZDB");
            //当前路径
            CurrentPath = Application.StartupPath + @"\KJ\Collect\";
            if (!Directory.Exists(CurrentPath))
            {
                Directory.CreateDirectory(CurrentPath);
            }
            //获取所有附件记录表
            dtLZ_KJ_CollectFile = LZdbHelper.Query("select top 100 Id,FK_Value,FIleName,FileExt,FileSize from FC_InfoAttach").Tables[0];
            dtS = DateTime.Now;
            TimeLog.AppendText("开始：" + dtS.ToString("yyyy-MM-dd HH:mm:ss:ff") + "\r");
            myDeleGates = new MyDeleGateBytesToFile[ThreadNum];
            results = new IAsyncResult[ThreadNum];            
            TimeLog.AppendText("总条数:" + dtLZ_KJ_CollectFile.Rows.Count.ToString() + "\r");
            int length = dtLZ_KJ_CollectFile.Rows.Count / ThreadNum;
            for (int i = 0; i < ThreadNum; i++)
            {
                myDeleGates[i] = new MyDeleGateBytesToFile(BytesToFile);
                int startNum = i * length;
                int endNum = 0;
                if (i == ThreadNum - 1)
                {
                    endNum = dtLZ_KJ_CollectFile.Rows.Count;
                }
                else
                {
                    endNum = (i + 1) * length;
                }
                AsyncCallback acb = new AsyncCallback(CallBackMethod);
                //i会加到results[i].AsyncState 在回调时用到
                results[i] = myDeleGates[i].BeginInvoke(startNum, endNum, acb, i);
                TimeLog.AppendText("线程[" + i.ToString() + "]记录起止数：" + startNum.ToString() + "-" + endNum.ToString() + "\r");
            }
        }

        /// <summary>
        /// 异步回调方法
        /// </summary>
        /// <param name="ar">开始异步时参数</param>
        private void CallBackMethod(IAsyncResult ar)
        {
            //不加锁的话 同时返回就会出错。
            lock (thisLock)
            {
                int i = (int)ar.AsyncState;
                DateTime dtE = DateTime.Now;                
                TimeLog.AppendText("线程[" + i.ToString() + "]结束于：" + dtE.ToString("yyyy-MM-dd HH:mm:ss:ff") + "\r");
                TimeSpan tsS = new TimeSpan(dtS.Ticks);
                TimeSpan tsE = new TimeSpan(dtE.Ticks);
                TimeSpan teR = tsE.Subtract(tsS);
                TimeLog.AppendText("用了：" + teR.TotalMilliseconds + "\r");
                LogTxt.AppendText(myDeleGates[i].EndInvoke(results[i]).ToString());//myDeleGates[i].EndInvoke(ar).ToString() 也可以
                CompleteNum = CompleteNum - 1;
                if (CompleteNum == 0)
                {                    
                    MessageBox.Show("导入完成");
                }
            }
        }


        /// <summary>
        /// 二进制转成文件 跟定义的委托相同的签名
        /// </summary>
        /// <param name="StartNum">开始数</param>
        /// <param name="EndNum">结束数</param>
        /// <returns>StringBuilder</returns>
        private StringBuilder BytesToFile(int StartNum, int EndNum)
        {
            StringBuilder sb = new StringBuilder();
            for (int i = StartNum; i < EndNum; i++)
            {
                DataRow dr = dtLZ_KJ_CollectFile.Rows[i];
                string FileName = CommandFunction.ObjectToStr(dtAllFsFileId.Select("LZFC_InfoAttach_Id='" + CommandFunction.ObjectToStr(dr["Id"]) + "'")[0]["FsFileId"]) + "_" + CommandFunction.ObjectToStr(dr["FIleName"]) + "." + CommandFunction.ObjectToStr(dr["FileExt"]);
                //CommandFunction.ObjectToStr(dr["Id"]) + "_" + CommandFunction.ObjectToStr(dr["FIleName"]) + "." + CommandFunction.ObjectToStr(dr["FileExt"]);
                string FullFilePath = "";
                FullFilePath = CurrentPath + FileName; 
                if (File.Exists(FullFilePath))
                {                    
                    sb.Append("[" + FileName + "]已经创建过\r");                    
                }
                else
                {
                    object FileData = LZdbHelper.GetSingle("select FileData from FC_InfoAttach where Id='" + dr["Id"].ToString() + "'");
                    Byte[] Files = (Byte[])FileData;
                    BinaryWriter bw = new BinaryWriter(File.Open(FullFilePath, FileMode.OpenOrCreate));
                    bw.Write(Files);
                    bw.Close();
                    sb.Append("创建文件[" + FileName + "]成功\r");
                }                
            }
            return sb;

        }

        //定义一个委托
        private delegate StringBuilder MyDeleGateBytesToFile(int StartNum, int EndNum);


    }
}

其中

 object FileData = LZdbHelper.GetSingle("select FileData from FC_InfoAttach where Id='" + dr["Id"].ToString() + "'");

去数据库取二进制数据时，如果该文件很大，程序会提示 数据库操作超时。

因此在GetSingle方法里面设置了一下超时时间

/// <summary>
        /// 执行一条计算查询结果语句，返回查询结果（object）。
        /// </summary>
        /// <param name="SQLString">计算查询结果语句</param>
        /// <returns>查询结果（object）</returns>
        public object GetSingle(string SQLString)
        {
            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                using (SqlCommand cmd = new SqlCommand(SQLString, connection))
                {
                    try
                    {
                        connection.Open();
                        //设置取数据时的超时时间
                        cmd.CommandTimeout = 0;
                        object obj = cmd.ExecuteScalar();
                        if ((Object.Equals(obj, null)) || (Object.Equals(obj, System.DBNull.Value)))
                        {
                            return null;
                        }
                        else
                        {
                            return obj;
                        }
                    }
                    catch (System.Data.SqlClient.SqlException e)
                    {
                        connection.Close();
                        throw e;
                    }
                }
            }
        }