深入理解游标Cursors，实现数据的快速查找，插入，删除，更新(转)

深入理解游标Cursors，实现数据的快速查找，插入，删除，更新

1、         查找数据Search Cursors  //by yl landgis@126.com  yanleigis@21cn.com 2008.7.7

 [C#]

//Create an envelope for the lower right portion of data

IEnvelope envelope = new EnvelopeClass();

envelope.PutCoords(508786, 681196, 513033, 684341);

 

// create a spatial query filter

ISpatialFilter spatialFilter = new SpatialFilterClass();

 

// specify the geometry to query with

spatialFilter.Geometry = envelope;

 

// specify what the geometry field is called on the Feature Class that we will querying against

String shpFld = featureClass.ShapeFieldName;

spatialFilter.GeometryField = shpFld;

 

// specify the type of spatial operation to use

spatialFilter.SpatialRel = esriSpatialRelEnum.esriSpatialRelIntersects;

// perform the query and use a cursor to hold the results

IQueryFilter queryFilter = new QueryFilterClass();

queryFilter = (IQueryFilter)spatialFilter;

 

IFeatureCursor searchCursor = featureClass.Search(queryFilter, true);//只查询，true快一些

 

IFeature feature = searchCursor.NextFeature();

int n = 0;

while (feature != null)

{

    n++;

    feature = baseCursor.NextFeature();

}

 

 

2、         插入数据Insert Cursors—目前数据插入最快的方法   //by yl landgis@126.com  yanleigis@21cn.com 2008.7.7

//Create the Feature Buffer

IFeatureBuffer featureBuffer = featureClass.CreateFeatureBuffer();

//Create insert feature cursor using buffering = true.

IFeatureCursor featureCursor = featureClass.Insert(true);

object featureOID;       

//All of the features to be created were installed by "B Pierce"

featureBuffer.set_Value(featureBuffer.Fields.FindField("InstBy"), "B Pierce");

for (int ic = 0; ic < 99; ic++) 

{

    //Set the featurebuffers's shape

    featureBuffer.Shape = geometry

    //Insert the feature into the feature cursor

    featureOID = featureCursor.InsertFeature(featureBuffer);

}

//All of the features to be created were installed by "K Johnston"

featureBuffer.set_Value(featureBuffer.Fields.FindField("InstBy"), "K Johnston");

for (int ic = 0; ic < 99; ic++)

{

    //Set the feature's shape

    featureBuffer.Shape = geometry

    //Insert the feature into the feature cursor

    featureOID = featureCursor.InsertFeature(featureBuffer);

}

featureCursor.Flush();

 

3、         数据删除 delete   //by yl landgis@126.com  yanleigis@21cn.com 2008.7.7

IFeatureClass featureClass = featureWorkspace.OpenFeatureClass(“Parcels”);

 

IQueryFilter queryFilter = new QueryFilterClass();

queryFilter.WhereClause = “ZONING_S = ‘R'”;

 

// use IFeatureClass::Update to populate IFeatureCursor

IFeatureCursor updateCursor = featureClass.Update(queryFilter, false);

 

IFeature feature = updateCursor.NextFeature();

 

int m = 0;

while (feature != null)

{

    m++;

    updateCursor.DeleteFeature(feature);

    feature = updateCursor.NextFeature();

}

 

 

4、         数据更新 update   //by yl landgis@126.com  yanleigis@21cn.com 2008.7.7

IFeatureClass featureClass =  featureWorkspace.OpenFeatureClass(“Parcels”);

 

// restrict the number of features to be updated.

IQueryFilter queryFilter = new QueryFilterClass();

queryFilter.WhereClause = “ZONING_S = ‘U'”;

 

// use IFeatureClass::Update to populate IFeatureCursor

IFeatureCursor updateCursor = featureClass.Update(queryFilter, false);

 

int fieldindex = featureClass.FindField(“ZONING_S”);

 

IFeature feature = updateCursor.NextFeature();

 

int m = 0;

while (feature != null)

{

    m++;

    feature.set_Value(fieldindex, “X”);

    updateCursor.UpdateFeature(feature);

    feature = updateCursor.NextFeature();

}