AnyCAD 是一款基于 C# 的二次開發庫，可以用于創建和操作 CAD 文件

1. 讀取和顯示 DWG 文件

using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.Runtime;

[CommandMethod("ReadAndDisplayDWG")]
public void ReadAndDisplayDWG()
{
    // 打開 DWG 文件
    Document doc = Application.DocumentManager.Open("path/to/your/file.dwg", false);
    Database db = doc.Database;

    // 獲取模型空間中的實體
    using (Transaction tr = db.TransactionManager.StartTransaction())
    {
        BlockTable bt = (BlockTable)tr.GetObject(db.BlockTableId, OpenMode.ForRead);
        BlockTableRecord modelSpace = (BlockTableRecord)tr.GetObject(bt[BlockTableRecord.ModelSpace], OpenMode.ForRead);

        // 遍歷實體并輸出信息
        foreach (ObjectId id in modelSpace)
        {
            Entity ent = (Entity)tr.GetObject(id, OpenMode.ForRead);
            ed.WriteMessage($"Entity type: {ent.GetType().Name}, Handle: {ent.Handle}\n");
        }

        tr.Commit();
    }
}

2. 創建并保存新的 DWG 文件

using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.Geometry;
using Autodesk.AutoCAD.Runtime;

[CommandMethod("CreateNewDWG")]
public void CreateNewDWG()
{
    // 創建新的數據庫
    Database db = new Database(false, true);

    // 添加一個線到模型空間
    using (Transaction tr = db.TransactionManager.StartTransaction())
    {
        BlockTable bt = (BlockTable)tr.GetObject(db.BlockTableId, OpenMode.ForRead);
        BlockTableRecord modelSpace = (BlockTableRecord)tr.GetObject(bt[BlockTableRecord.ModelSpace], OpenMode.ForWrite);

        Line line = new Line(new Point3d(0, 0, 0), new Point3d(100, 100, 0));
        modelSpace.AppendEntity(line);
        tr.AddNewlyCreatedDBObject(line, true);

        tr.Commit();
    }

    // 保存新的 DWG 文件
    db.SaveAs("path/to/your/new/file.dwg");
}

3. 修改 DWG 文件中的實體

using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.Runtime;

[CommandMethod("ModifyDWGEntity")]
public void ModifyDWGEntity()
{
    // 打開 DWG 文件
    Document doc = Application.DocumentManager.Open("path/to/your/file.dwg", false);
    Database db = doc.Database;

    // 修改模型空間中的第一個實體
    using (Transaction tr = db.TransactionManager.StartTransaction())
    {
        BlockTable bt = (BlockTable)tr.GetObject(db.BlockTableId, OpenMode.ForRead);
        BlockTableRecord modelSpace = (BlockTableRecord)tr.GetObject(bt[BlockTableRecord.ModelSpace], OpenMode.ForRead);

        // 獲取第一個實體并修改其屬性
        ObjectId firstEntityId = modelSpace.OfType<ObjectId>().FirstOrDefault();
        if (firstEntityId.IsValid)
        {
            Entity firstEntity = (Entity)tr.GetObject(firstEntityId, OpenMode.ForWrite);
            firstEntity.ColorIndex = 2; // 將實體顏色更改為紅色
        }

        tr.Commit();
    }

    // 保存修改后的 DWG 文件
    db.SaveAs("path/to/your/modified/file.dwg");
}

這些示例展示了如何使用 AnyCAD 進行基本的 CAD 文件操作。根據需求，你可以在此基礎上進行更多的擴展和定制。