C# AutoCAD2010在打开的dwg中选择块，在该位置上再选择外部块将其替换，其他名字一样但位置不一样的块不替换的完整代码

以下是示例代码，可以参考：

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

namespace ReplaceBlock
{
    public class Commands
    {
        [CommandMethod("REPLACEBLOCK")]
        public void ReplaceBlock()
        {
            Document doc = Application.DocumentManager.MdiActiveDocument;
            Editor ed = doc.Editor;

            // 选择外部块
            ed.WriteMessage("\n选择要替换的块：");
            PromptEntityOptions peo = new PromptEntityOptions("\n选择要替换的块：");
            peo.SetRejectMessage("\n只能选择块。");
            peo.AddAllowedClass(typeof(BlockReference), true);
            PromptEntityResult per = ed.GetEntity(peo);
            if (per.Status != PromptStatus.OK) return;
            BlockReference extBlock = (BlockReference)per.ObjectId.GetObject(OpenMode.ForRead);

            // 获取外部块的属性
            BlockTableRecord extBtr = (BlockTableRecord)extBlock.BlockTableRecord.GetObject(OpenMode.ForRead);
            string extBlockName = extBtr.Name;
            Point3d extPosition = extBlock.Position;

            // 选择位置块
            ed.WriteMessage("\n选择要替换的位置：");
            PromptEntityOptions peo2 = new PromptEntityOptions("\n选择要替换的位置：");
            peo2.SetRejectMessage("\n只能选择块。");
            peo2.AddAllowedClass(typeof(BlockReference), true);
            PromptEntityResult per2 = ed.GetEntity(peo2);
            if (per2.Status != PromptStatus.OK) return;
            BlockReference posBlock = (BlockReference)per2.ObjectId.GetObject(OpenMode.ForRead);

            // 获取位置块的属性
            BlockTableRecord posBtr = (BlockTableRecord)posBlock.BlockTableRecord.GetObject(OpenMode.ForRead);
            string posBlockName = posBtr.Name;
            Point3d posPosition = posBlock.Position;

            // 判断是否为同一块
            if (posBlockName != extBlockName)
            {
                ed.WriteMessage("\n选择的位置块名称与外部块名称不相同，无法替换。");
                return;
            }

            // 替换块
            using (Transaction tr = doc.TransactionManager.StartTransaction())
            {
                BlockTable bt = (BlockTable)tr.GetObject(doc.Database.BlockTableId, OpenMode.ForRead);
                BlockTableRecord btr = (BlockTableRecord)tr.GetObject(bt[BlockTableRecord.ModelSpace], OpenMode.ForWrite);

                foreach (ObjectId id in btr)
                {
                    if (id.ObjectClass == RXClass.GetClass(typeof(BlockReference)))
                    {
                        BlockReference block = (BlockReference)tr.GetObject(id, OpenMode.ForWrite);
                        if (block.BlockTableRecord != extBtr.Id) continue;
                        if (block.Position != posPosition) continue;
                        block.BlockTableRecord = extBtr.Id;
                        block.Position = extPosition;
                    }
                }

                tr.Commit();
            }

            ed.WriteMessage("\n块替换完成。");
        }
    }
}

该代码中，通过选择外部块和位置块，判断它们是否为同一块，然后遍历模型空间中的所有块，如果位置块与外部块名称相同且位置相同，则替换为外部块。其他名称相同但位置不同的块不会被替换。