IFeatureClass.Search(IQuery Filter,bool Recycling)中得Recycling参数说明(转)

FeatureClass的Search方法大家经常用到，很多人对Search方法的其中一个参数bool Recycling不是很理解。先做以下解释： 

1.pFeatureCursor存储的是所有符合条件的Feature对象的引用，
2.Recycling的意思是回收，参数Recycling为True的时当执行这个方法IFeature pFeature=pFeatureCursor.NextFeature()上一条记录的图形值在内存中所占的地址就会被销毁回收，为False的时候当执行这个方法IFeature pFeature=pFeatureCursor.NextFeature()上一条记录的图形值依然存在在内存中。

a.参数Recycling设置为True

　　

IFeatureClass pFeatureClass = (this.axMapControl1.get_Layer(0) as IFeatureLayer).FeatureClass;

IFeatureCursor pFeatureCursor = pFeatureClass.Search(null, true);
 //IFeatureCursor pFeatureCursor = pFeatureClass.Search(null, false);
 List<IFeature> pFeatures = new List<IFeature>();
IFeature pFeature = pFeatureCursor.NextFeature();
while (pFeature != null)
 {
 pFeatures.Add(pFeature);
 pFeature = pFeatureCursor.NextFeature();
 }
 for (int i = 0; i < pFeatures.Count; i++)
 {
 MessageBox.Show(((pFeatures.Shape as IPolygon) as IArea).Area.ToString());
 }

 

分析：pFeatures集合存储了指向FeatureClass上所有Feature的引用，但是由于Recycling参数设置为TRUE也就是说每执行一个NextFeautre方法上一条记录的Feature值在内存中被回收，所以到最后遍历pFeatures集合的时候所有的IFeature引用指向的Feature对象都为Null。所以会引发一下错误（如下图所示）：

b.参数Recycling设置为False

 IFeatureClass pFeatureClass = (this.axMapControl1.get_Layer(0) as IFeatureLayer).FeatureClass;
 //IFeatureCursor pFeatureCursor = pFeatureClass.Search(null, true);
 IFeatureCursor pFeatureCursor = pFeatureClass.Search(null, false);
 List<IFeature> pFeatures = new List<IFeature>();
 IFeature pFeature = pFeatureCursor.NextFeature();
 while (pFeature != null)
 {
 pFeatures.Add(pFeature);
 pFeature = pFeatureCursor.NextFeature();
 }
 for (int i = 0; i < pFeatures.Count; i++)
 {
 MessageBox.Show(((pFeatures.Shape as IPolygon) as IArea).Area.ToString());
 }

 

分析：pFeatures集合存储了指向FeatureClass上所有Feature的引用，但是由于Recycling参数设置为False也就是说每执行一个NextFeautre方法上一条记录的Feature值在内存中依然存在，所以到最后遍历pFeatures集合的时候所有的IFeature引用指向的Feature对象都依然存在。所以会执行的很Happy（如下图所示）：

  更多GIS开发相关问题请加入 GIS开发学习QQ交流群 192251607 共同交流学习！