C# AutoCAD2010选择dwg中的一个块，获取其位置后，再在电脑本地选择一个外部块，在该位置去替换它

你可以通过以下步骤来实现这个功能：

1. 使用 AutoCAD 的 .NET API 选择 dwg 中的块，获取其位置。

2. 使用 C# 的 OpenFileDialog 类选择本地的外部块文件。

3. 使用 AutoCAD 的 .NET API 创建外部块的副本，并将其插入到 dwg 中原来块的位置。

下面是示例代码：

// 选择 dwg 中的块，获取其位置
PromptEntityOptions promptEntityOptions = new PromptEntityOptions("\n请选择块：");
promptEntityOptions.SetRejectMessage("\n请选择块。");
promptEntityOptions.AddAllowedClass(typeof(BlockReference), true);
PromptEntityResult promptEntityResult = acDocEditor.GetEntity(promptEntityOptions);
if (promptEntityResult.Status != PromptStatus.OK)
{
    return;
}
ObjectId blockId = promptEntityResult.ObjectId;
BlockReference blockReference = transaction.GetObject(blockId, OpenMode.ForRead) as BlockReference;
Point3d blockPosition = blockReference.Position;

// 选择本地的外部块文件
OpenFileDialog openFileDialog = new OpenFileDialog();
openFileDialog.Filter = "DWG files (*.dwg)|*.dwg";
if (openFileDialog.ShowDialog() != DialogResult.OK)
{
    return;
}
string blockFilePath = openFileDialog.FileName;

// 创建外部块的副本，并将其插入到 dwg 中原来块的位置
Database blockDatabase = new Database(false, true);
blockDatabase.ReadDwgFile(blockFilePath, FileOpenMode.OpenForReadAndAllShare, true, "");
using (Transaction blockTransaction = blockDatabase.TransactionManager.StartTransaction())
{
    BlockTable blockTable = blockTransaction.GetObject(blockDatabase.BlockTableId, OpenMode.ForRead) as BlockTable;
    BlockTableRecord blockTableRecord = blockTransaction.GetObject(blockTable[BlockTableRecord.ModelSpace], OpenMode.ForWrite) as BlockTableRecord;
    BlockTableRecord blockRecord = blockTransaction.GetObject(blockTable[blockTableRecord.Name], OpenMode.ForRead) as BlockTableRecord;
    foreach (ObjectId objectId in blockRecord)
    {
        Entity entity = blockTransaction.GetObject(objectId, OpenMode.ForRead) as Entity;
        BlockReference blockRef = entity as BlockReference;
        if (blockRef != null)
        {
            BlockTableRecord blockDef = blockTransaction.GetObject(blockRef.BlockTableRecord, OpenMode.ForRead) as BlockTableRecord;
            BlockReference newBlockRef = new BlockReference(blockPosition, blockDef.ObjectId);
            blockTableRecord.AppendEntity(newBlockRef);
            blockTransaction.AddNewlyCreatedDBObject(newBlockRef, true);
        }
    }
    blockTransaction.Commit();
}

请注意，这只是一个示例代码，你需要根据实际情况进行修改和完善。同时要注意保护用户数据隐私和安全性。