IFeatureCache m_FeatureCache;
bool m_CacheFilled;
public bool Snap(IFeatureClass featureClass, IPoint point, double tolerance)
// 参数 featureClass 是要捕捉的图层的 featureClass
// 参数 point 是鼠标所在点，把它传进来，最后要返回捕捉到的点
// 参数 tolerance 用来设置捕捉容差，比如屏幕上捕捉7个像素范围内的对象
{
int Index = 0;
double Dist, minDist;
IFeature feature; 
IPoint pCachePt, pSnapPt;
IProximityOperator pProximity = (IProximityOperator)point;
minDist = tolerance * 10;
if (m_FeatureCache == null)
m_FeatureCache = new FeatureCacheClass();
if (featureClass == null)
return false;
if (!m_CacheFilled)
{
FillCache(featureClass, point, 10);
m_CacheFilled = true;
}
if (!m_FeatureCache.Contains(point))
FillCache(featureClass, point, tolerance * 10);
pCachePt = new PointClass ();
for (int Count = 0; Count < m_FeatureCache.Count; Count++)
{
feature = m_FeatureCache.get_Feature(Count);
if (feature.Shape.GeometryType == esriGeometryType.esriGeometryPoint)
{
pCachePt = (IPoint)feature.Shape; // 取到一点
}
else
return false;
Dist = pProximity.ReturnDistance(pCachePt); // 判断点到鼠标当前点的距离
if (Dist < minDist)　 
{
Index = Count;
minDist = Dist;
}
}
if (minDist >= tolerance) // 如果最小距离大于设置的容差,则不捕捉
return false;
feature = m_FeatureCache.get_Feature(Index); 
pSnapPt = pCachePt; // 取距离最近的点为最后捕捉到的点
point.PutCoords(pSnapPt.X, pSnapPt.Y); // 把捕捉到的点的坐标传给鼠标当前点
return true;
}

private void FillCache(IFeatureClass featureClass, IPoint pPoint, double Distance)
{
m_FeatureCache.Initialize(pPoint, Distance); // 设置缓存
m_FeatureCache.AddFeatures(FClass); // 把featureclass中的feature提取到缓存中
}