C# AutoCAD2010在dwg中选择块，在该位置上选择外部块将其替换，其他位置不一样但名字一样的块不替换的完整代码

以下是可能的实现方法，仅供参考：

// 获取当前文档和数据库
Document doc = Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument;
Database db = doc.Database;

// 获取用户选择的块
PromptEntityOptions promptOptions = new PromptEntityOptions("请选择要替换的块：");
promptOptions.SetRejectMessage("\n只能选择块！");
promptOptions.AddAllowedClass(typeof(BlockReference), true);
PromptEntityResult promptResult = doc.Editor.GetEntity(promptOptions);

if (promptResult.Status != PromptStatus.OK) {
    return;
}

// 获取要替换的外部块的路径和名称
PromptOpenFileOptions fileOptions = new PromptOpenFileOptions("请选择要替换的外部块：");
fileOptions.Filter = "DWG 文件 (*.dwg)|*.dwg";
PromptFileNameResult fileResult = doc.Editor.GetFileNameForOpen(fileOptions);
if (fileResult.Status != PromptStatus.OK) {
    return;
}

string blockName = ""; // 要替换的块的名称
ObjectId blockId = promptResult.ObjectId; // 要替换的块的 ID

using (Transaction trans = db.TransactionManager.StartTransaction()) {
    // 获取块的名称
    BlockReference blockRef = trans.GetObject(blockId, OpenMode.ForRead) as BlockReference;
    blockName = blockRef.Name;
    trans.Commit();
}

// 打开外部块所在的数据库并检查其中是否存在要替换的块
Database externalDb = new Database(false, true);
externalDb.ReadDwgFile(fileResult.StringResult, FileOpenMode.OpenForReadAndAllShare, true, "");
using (Transaction trans = externalDb.TransactionManager.StartTransaction()) {
    BlockTable bt = trans.GetObject(externalDb.BlockTableId, OpenMode.ForRead) as BlockTable;
    if (!bt.Has(blockName)) {
        doc.Editor.WriteMessage("\n外部块中不存在名称为 " + blockName + " 的块！");
        return;
    }
    trans.Commit();
}

// 选择要替换的块的位置并进行替换
Editor ed = doc.Editor;
Point3d basePt = Point3d.Origin;
PromptPointOptions basePtOpts = new PromptPointOptions("\n选择块的位置进行替换：");
basePtOpts.AllowNone = false;
PromptPointResult basePtRes = ed.GetPoint(basePtOpts);
basePt = basePtRes.Value;

using (Transaction trans = db.TransactionManager.StartTransaction()) {
    BlockTable btr = (BlockTable)trans.GetObject(db.BlockTableId, OpenMode.ForRead);
    BlockTableRecord ms = (BlockTableRecord)trans.GetObject(btr[BlockTableRecord.ModelSpace], OpenMode.ForWrite);

    // 遍历 ModelSpace 中的所有块参照并进行替换
    foreach (ObjectId id in ms) {
        Entity ent = trans.GetObject(id, OpenMode.ForRead) as Entity;

        if (ent is BlockReference && ent.ObjectId == blockId) {
            BlockReference blockRef = ent as BlockReference;

            if (blockRef.Position.DistanceTo(basePt) < Tolerance.Global.EqualPoint) {
                // 创建外部块的新实例并替换原有的块参照
                BlockReference newBlockRef = new BlockReference(blockRef.Position, externalDb.BlockTable[blockName]);
                newBlockRef.ScaleFactors = blockRef.ScaleFactors;
                newBlockRef.Rotation = blockRef.Rotation;

                // 复制属性值
                foreach (DynamicBlockReferenceProperty prop in blockRef.DynamicBlockReferencePropertyCollection) {
                    newBlockRef.DynamicBlockReferencePropertyCollection[prop.PropertyName] = prop.Value;
                }

                // 删除原有的块参照并添加新的块参照
                ObjectId newId = ms.AppendEntity(newBlockRef);
                trans.AddNewlyCreatedDBObject(newBlockRef, true);
                ms.Remove(blockRef.ObjectId);
                ed.WriteMessage("\n名称为 " + blockName + " 的块已被成功替换！");
                break;
            }
        }
    }

    trans.Commit();
}

这段代码的思路如下：

1. 提示用户选择要替换的块，并获取其 ID 和名称；
2. 提示用户选择要替换的外部块的 DWG 文件，并检查其中是否存在名称为要替换的块的名称；
3. 让用户选择要替换的块的位置，并遍历 ModelSpace 中的所有块参照，找到与要替换的块 ID 相同且位置相同的块参照；
4. 创建外部块的新实例，并将其属性值复制到原有的块参照中；
5. 删除原有的块参照并添加新的块参照，完成块的替换。