Arcengine效率探究之一——属性的读取

在写一个对属性表的统计函数时,发现执行速度奇慢无比,百思不得其解,其实算法并不复杂,后来逐句排查终于发现竟是Arcengine的函数读取属性值的问题。

在获取属性表的值时有多种方法:

方法一:

ITable pTable = pLayer.FeatureClass as ITable;

clsFldValue = pTable.GetRow(i).get_Value(3);

 方法二:

IFeatureCursor FCursor = pLayer.FeatureClass.Search(new QueryFilterClass(), false);

IFeature feature = FCursor.NextFeature();

if (feature == null) return null;

clsFldValue = feature.get_Value(clsFldIndex);

feature = FCursor.NextFeature();

 

Environment.TickCount进行代码执行时间测试,结果发现方法一读取整个表的时间为4984ms,而方法二读取同一个属性给的时间仅为32 ms,法二的执行效率是法一的156倍!!!完整测试代码如下:

 

IFeatureLayer pLayer = Utilities.GetLayerByName((string)cmbRegLayers.SelectedItem, m_mapControl) as IFeatureLayer;

 

            IFeatureCursor FCursor = pLayer.FeatureClass.Search(new QueryFilterClass(), false);

            IFeature feature = FCursor.NextFeature();

            int t = Environment.TickCount;

             object clsFldValue=null;

             for (int i = 0; i < pLayer.FeatureClass.FeatureCount(null); i++)

             {

                 clsFldValue = feature.get_Value(3);

                 feature = FCursor.NextFeature();

             }

            t = Environment.TickCount - t;

            MessageBox.Show(t.ToString());

 

            ITable pTable = pLayer.FeatureClass as ITable;

            t = Environment.TickCount;

            for (int i = 0; i < pTable.RowCount(null); i++)

                clsFldValue = pTable.GetRow(i).get_Value(3);

            t = Environment.TickCount - t;

            MessageBox.Show(t.ToString());

 

至于为什么使用ITable 读取属性值速度如此之慢,不得而知,望有高人指点。

另外,在ESRI中国社区中也有一帖子讨论执行速度的问题,或者能为类似问题做些提示。此贴内容如下:

 

 

 

目标是想将原数据库中的点信息(x,y经纬度坐标,度格式),添加到FeatureClass中,数据库中大概有10000条数据,全部添加到FeatureClass中大概需要半小时以上

DataSet ds = loadExcel("d://aaa.xls");

IFeature feature = featureClass.CreateFeature();

IFields fields = featureClass.Fields;

for(int i=0;i

{

     DataRow row = ds.Tables[0].Rows[i];

     string xl = Convert.ToString(row[0]);

     string x = Convert.ToDouble(row[1]);

     string y = Convert.ToDouble(row[2]);

     //....其它数据库中字段

 

     //创建点对象

     IPoint point = new PointClass();

     point.X = x;

     point.Y = y;

 

     //设置Fields域

     feature.set_Value(fields.FindField("线路"),xl);

     feature.set_Value(fields.FindField("经度"),x); 

     feature.set_Value(fields.FindField("纬度"),y); 

     //保存点对象

     feature.Shape = point;

     feature.Store();

}

 

改进后:

 

DataSet ds = loadExcel("d://aaa.xls");

IFeatureBuffer featureBuffer;

IFeatureCursor cur = featureClass.Insert(true);

IPoint point;

IFields fields = featureClass.Fields;

for(int i=0;i

{

     DataRow row = ds.Tables[0].Rows[i];

     string xl = Convert.ToString(row[0]);

     string x = Convert.ToDouble(row[1]);

     string y = Convert.ToDouble(row[2]);

     //....其它数据库中字段

 

   //创建点对象

   point = new PointClass();

     point.X = x;

     point.Y = y;

 

     featureBuffer = featureClass.CreateFeatureBuffer();

     //设置Fields域

   featureBuffer.set_Value(fields.FindField("线路"),xl);

     featureBuffer.set_Value(fields.FindField("经度"),x); 

     featureBuffer.set_Value(fields.FindField("纬度"),y); 

     //保存点对象

   featureBuffer.Shape = point;

     cur.InsertFeature(featureBuffer);

}

可以看出改进后使用了eatureClass.CreateFeatureBuffer方法,使效率大大提高。

 

 

 

 

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