//在不使用任務插件的情況下讀取DWG文件的縮略圖，以便在沒有安裝AutoCAD的計算機上瀏覽。


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


namespace 瀏覽dwg
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }


        private void Form1_Load(object sender, EventArgs e)
        {
            ViewDWG viewDwg = new ViewDWG();
            pictureBox1.Image = viewDwg.GetDwgImage("c:\\1.dwg");
        }
        class ViewDWG
        {
            struct BITMAPFILEHEADER
            {
                public short bfType;
                public int bfSize;
                public short bfReserved1;
                public short bfReserved2;
                public int bfOffBits;
            }
            public Image GetDwgImage(string FileName)
            {
                if (!(File.Exists(FileName)))
                {
                    throw new FileNotFoundException("文件沒有被找到");
                }
                FileStream DwgF; //文件流
                int PosSentinel; //文件描述塊的位置
                BinaryReader br; //讀取二進制文件
                int TypePreview; //縮略圖格式
                int PosBMP;       //縮略圖位置
                int LenBMP;       //縮略圖大小
                short biBitCount; //縮略圖比特深度
                BITMAPFILEHEADER biH; //BMP文件頭，DWG文件中不包含位圖文件頭，要自行加上去
                byte[] BMPInfo;       //包含在DWG文件中的BMP文件體
                MemoryStream BMPF = new MemoryStream(); //保存位圖的內(nèi)存文件流
                BinaryWriter bmpr = new BinaryWriter(BMPF); //寫二進制文件類
                Image myImg = null;
                try
                {
                    DwgF = new FileStream(FileName, FileMode.Open, FileAccess.Read);   //文件流
                    br = new BinaryReader(DwgF);
                    DwgF.Seek(13, SeekOrigin.Begin); //從第十三字節(jié)開始讀取
                    PosSentinel = br.ReadInt32(); //第13到17字節(jié)指示縮略圖描述塊的位置
                    DwgF.Seek(PosSentinel + 30, SeekOrigin.Begin); //將指針移到縮略圖描述塊的第31字節(jié)
                    TypePreview = br.ReadByte(); //第31字節(jié)為縮略圖格式信息，2 為BMP格式，3為WMF格式
                    if (TypePreview == 1)
                    {
                    }
                    else if (TypePreview == 2 || TypePreview == 3)
                    {
                        PosBMP = br.ReadInt32(); //DWG文件保存的位圖所在位置
                        LenBMP = br.ReadInt32(); //位圖的大小
                        DwgF.Seek(PosBMP + 14, SeekOrigin.Begin); //移動指針到位圖塊
                        biBitCount = br.ReadInt16(); //讀取比特深度
                        DwgF.Seek(PosBMP, SeekOrigin.Begin); //從位圖塊開始處讀取全部位圖內(nèi)容備用
                        BMPInfo = br.ReadBytes(LenBMP); //不包含文件頭的位圖信息
                        br.Close();
                        DwgF.Close();
                        biH.bfType = 19778; //建立位圖文件頭
                        if (biBitCount < 9)
                        {
                            biH.bfSize = 54 + 4 * (int)(Math.Pow(2, biBitCount)) + LenBMP;
                        }
                        else
                        {
                            biH.bfSize = 54 + LenBMP;
                        }
                        biH.bfReserved1 = 0; //保留字節(jié)
                        biH.bfReserved2 = 0; //保留字節(jié)
                        biH.bfOffBits = 14 + 40 + 1024; //圖像數(shù)據(jù)偏移
                        //以下開始寫入位圖文件頭
                        bmpr.Write(biH.bfType); //文件類型
                        bmpr.Write(biH.bfSize); //文件大小
                        bmpr.Write(biH.bfReserved1); //0
                        bmpr.Write(biH.bfReserved2); //0
                        bmpr.Write(biH.bfOffBits); //圖像數(shù)據(jù)偏移
                        bmpr.Write(BMPInfo); //寫入位圖
                        BMPF.Seek(0, SeekOrigin.Begin); //指針移到文件開始處
                        myImg = Image.FromStream(BMPF); //創(chuàng)建位圖文件對象
                        bmpr.Close();
                        BMPF.Close();
                    }
                    return myImg;
                }
                catch (Exception ex)
                {
                    throw new Exception(ex.Message);
                }
            }
        }


    }
}

using System;
using System.IO;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;

Database db = new Database(false, true);
try
{
//把DWG文件讀入到一個臨時的內(nèi)存數(shù)據(jù)庫中
db.ReadDwgFile(fullFileName, System.IO.FileShare.ReadWrite, true, null);
//現(xiàn)在進入數(shù)據(jù)庫并獲得數(shù)據(jù)庫的塊表引用
BlockTable bt = (BlockTable)trans.GetObject(db.BlockTableId, OpenMode.ForRead, false, true);
//從塊表的模型空間特性中獲得塊表記錄,塊表記錄對象包含DWG文件數(shù)據(jù)庫實體
BlockTableRecord btr = (BlockTableRecord)trans.GetObject(bt[BlockTableRecord.ModelSpace], OpenMode.ForRead, false, true);
foreach (ObjectId btrId in btr)
{
DBObject entBlock = (DBObject)trans.GetObject(btrId, OpenMode.ForRead, false, true);
if (entBlock.GetRXClass().DxfName.ToUpper() == “INSERT”)
{
BlockReference bRef = (BlockReference)entBlock;
if (bRef.AttributeCollection.Count != 0)
{
System.Collections.IEnumerator bRefEnum = bRef.AttributeCollection.GetEnumerator();
while (bRefEnum.MoveNext())
{
ObjectId aId = (ObjectId)bRefEnum.Current;//這一句極其關鍵
AttributeReference aRef = (AttributeReference)trans.GetObject(aId, OpenMode.ForRead, false, true);
aRef.TextString;//此語句即獲得屬性單行文本,請自行在此語句前添加 屬性單行文本 賦于的變量
}
}
}
}
trans.Commit(); //提交事務處理
btr.Dispose();
bt.Dispose();
}
catch (System.Exception ex)
{
MessageBox.Show(“\n出錯啦: ” + ex.Message);
}
finally
{
db.Dispose();
}