ArcEngine效率探究之二——属性的更新

修改一批要素的属性有多种方法，当数据量较大时，若选择不当可能会大大影响速度。

一、IRowBuffer 方法

此法适用于将一批数据更新为某一相同的属性。

IQueryFilter pFilter = new QueryFilterClass();
pFilter.WhereClause = "Z='T'";
pFilter.SubFields = "Z";
int nIndex = pFeatureClass.FindField("Z");
ITable pTable = pFeatureClass as ITable;
IRowBuffer pBuffer = pTable.CreateRowBuffer();
pBuffer.set_Value(nIndex, "TT");
pTable.UpdateSearchedRows(pFilter, pBuffer);
Marshal.ReleaseComObject(pFilter);

当所要更新的属性各不相同时，上述方法就不能用了。

二、逐条更新记录

这种方式中可有三种方法，如下：

（1）

for (int i = 0; i < pTable.RowCount(null); i++)
{
pRow = pTable.GetRow(i);
pRow.set_Value(2, i + 6);
pRow.Store();
}

（2）

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

for (int i = 0; i < featureNum; i++)
{

feature.set_Value(2, i);
feature.Store();
feature = FCursor.NextFeature();
}

（3）

ICursor pCursor =pTable.Update(null, false);
pRow = pCursor.NextRow();
for (int i = 0; i < pTable.RowCount(null); i++)
{
pRow.set_Value(2, i + 6);
pCursor.UpdateRow(pRow);
pRow = pCursor.NextRow();

}

试验数据为320条记录，三种方法的运行时间为：法（1）为40297ms;法（2）34922ms为;法（3）为219ms.

可见运用IFeature和IRow的Store方法更新速度都很慢，用ICursor 的UpdateRow方法速度很快，分别是前两者效率的184倍、159倍！！完整测试代码如下：

IFeatureLayer pLayer = Utilities.GetLayerByName((string)cmbRegLayers.SelectedItem, m_mapControl) as IFeatureLayer;
ITable pTable = pLayer.FeatureClass as ITable;
int t = 0;

IFeatureCursor FCursor = pLayer.FeatureClass.Search(new QueryFilterClass(), false);
IFeature feature = FCursor.NextFeature();
int featureNum = pLayer.FeatureClass.FeatureCount(null);
t = Environment.TickCount;
for (int i = 0; i < featureNum; i++)
{

feature.set_Value(2, i);
feature.Store();
feature = FCursor.NextFeature();
}
t = Environment.TickCount - t;
MessageBox.Show(t.ToString());


t = Environment.TickCount;
ICursor pCursor =pTable.Update(null, false);
IRow pRow = pCursor.NextRow();
for (int i = 0; i < pTable.RowCount(null); i++)
{
pRow.set_Value(2, i + 6);
pCursor.UpdateRow(pRow);
pRow = pCursor.NextRow();

}

t = Environment.TickCount - t;
MessageBox.Show(t.ToString());


t = Environment.TickCount;
for (int i = 0; i < pTable.RowCount(null); i++)
{
pRow = pTable.GetRow(i);
pRow.set_Value(2, i + 6);
pRow.Store();
}

t = Environment.TickCount - t;
MessageBox.Show(t.ToString());