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Reading Data#

One of the major benefits of using the ESRI platform it allows you to perform spatial and attribute based queries against the data to validate and perform analysis. As a side-effect, the same set of APIs are reused, which leads to code-duplication and/or memory management issues if used improperly.

Fetch#

The ITable and IFeatureClass interfaces have been extended to include Fetch methods that simplifies queries by abstracting the complexities while enforcing the proper memory management for the COM objects.

Method | Description :-----------------------|:------------------------------|:----------------------| Fetch(params int[]) | Fetch the features (or rows) that have the specified object identifiers using a non-recycling cursor. Fetch(IQueryFilter) | Fetch the features (or rows) that statisfy the query using a non-recycling cursor. Fetch(IQueryFilter, Action, bool) | Fetch the features (or rows) that statisfy the query and execute the action each.

  • Fetch features or rows with a list of OBJECTIDs.

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    IEditor editor = ArcMap.Application.GetEditor();
IWorkspace workspace = editor.EditWorkspace;

IFeatureClass transformers = workspace.GetFeatureClass("Transformers");
List<IFeature> features = transformers.Fetch(1,2,3,4,5,6);

  • Fetch features or rows that need a spatial and/or attribute dependencies to filter the results.

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    IEditor editor = ArcMap.Application.GetEditor();
IWorkspace workspace = editor.EditWorkspace;

IFeatureClass workRequests = workspace.GetFeatureClass("WorkRequests");
IFeatureClass transformers = workspace.GetFeatureClass("Transformers");
IFeature workRequest = workRequests.Fetch(1);
ISpatialFilter filter = new SpatialFilterClass();
filter.WhereClause = transformers.OIDFieldName + " IN (1,2,3,4,5,6)";
filter.Geometry = workRequest.Shape;
filter.SpatialRel = esriSpatialRelEnum.esriSpatialRelIntersects;
filter.GeometryField = "SHAPE";

List<IFeature> features = transformers.Fetch(filter);

  • Fetch features or rows that need actions performed but the memory can be recycled.

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    IEditor editor = ArcMap.Application.GetEditor();
IWorkspace workspace = editor.EditWorkspace;

IFeatureClass transformers = workspace.GetFeatureClass("Transformers");
int i = transformers.FindField("DATEMODIFIED");

IQueryFilter filter = new QueryFilterClass();
filter.WhereClause = transformers.OIDFieldName + " IN (1,2,3,4,5,6)";

int rowsAffected = transformers.Fetch(filter, feature =>
{
    feature.set_Value(i, DateTime.Now);
    feature.Store();
});

  • Fetch features or rows with a projection.

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    IEditor editor = ArcMap.Application.GetEditor();
IWorkspace workspace = editor.EditWorkspace;

IFeatureClass workRequests = workspace.GetFeatureClass("WorkRequests");
IFeatureClass transformers = workspace.GetFeatureClass("Transformers");
IFeature workRequest = workRequests.Fetch(1);
ISpatialFilter filter = new SpatialFilterClass();
filter.WhereClause = transformers.OIDFieldName + " IN (1,2,3,4,5,6)";
filter.Geometry = workRequest.Shape;
filter.SpatialRel = esriSpatialRelEnum.esriSpatialRelIntersects;
filter.GeometryField = "SHAPE";

List<int> oids = transformers.Fetch(filter, feature => feature.OID);