#region 提取一个图层上的各类元素
[CommandMethod("BlockInLayerCAD")]
public void BlockInLayerCAD()
{
Document ed = Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument;
Database db = HostApplicationServices.WorkingDatabase;

        //PromptStringOptions pStringOption = new PromptStringOptions("\\n 输入一个图层名");  
        //PromptResult layerName = pDocument.Editor.GetString(pStringOption);  
        List<string> layerNames = new List<string>();  
        using (Transaction tran = db.TransactionManager.StartTransaction())  
        {  
            #region 获取图层名字  
            LayerTable pLayerTable = tran.GetObject(db.LayerTableId, OpenMode.ForRead) as LayerTable;  
            foreach (ObjectId pObjectId in pLayerTable)  
            {  
                LayerTableRecord pLayerTableRecord = tran.GetObject(pObjectId, OpenMode.ForRead) as LayerTableRecord;  
                layerNames.Add(pLayerTableRecord.Name);  
            }  
            #endregion  
            string layerName = layerNames\[0\];  
            string typeResult ="文字";

            TypedValue\[\] pTypedValue = new TypedValue\[\] { new TypedValue((int)DxfCode.LayerName, layerName) };  
            SelectionFilter pSelectFilter = new SelectionFilter(pTypedValue);  
            PromptSelectionResult pSelectionResult = ed.Editor.SelectAll(pSelectFilter);  
            SelectionSet pSelectionSet = pSelectionResult.Value;  
            Point3d startPoint = new Point3d();  
            Point3d endPoint = new Point3d();  
            if (typeResult != "全部")  
            {  
                PromptPointOptions txtPoint = new PromptPointOptions("\\n 选择两个点作为文字取值范围");  
                txtPoint.Message = "\\n 选择第一个点：";  
                PromptPointResult txtStartPoint = ed.Editor.GetPoint(txtPoint);  
                startPoint = txtStartPoint.Value;  
                txtPoint.Message = "\\n 选择第二个点：";  
                PromptPointResult txtEndPoint = ed.Editor.GetPoint(txtPoint);  
                endPoint = txtEndPoint.Value;  
            }  
            foreach (ObjectId selectedId in pSelectionSet.GetObjectIds())  
            {  
                Entity pEntity = tran.GetObject(selectedId, OpenMode.ForRead) as Entity;  
                switch (typeResult)  
                {  
                    case "文字":  
                        if ((pEntity as MText) != null)  
                        {  
                            MText mText = pEntity as MText;  
                            if (mText.Location.X > startPoint.X && mText.Location.Y < startPoint.Y && mText.Location.X < endPoint.X && mText.Location.Y > endPoint.Y)  
                            {  
                                Autodesk.AutoCAD.ApplicationServices.Application.ShowAlertDialog((pEntity as MText).Text);  
                            }  
                        }  
                        break;  
                }  
            }  
            tran.Commit();  
        }  
    }  

#endregion