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LINQ

The while statement is used in conjunction with the ArcFM and ArcGIS APIs to iterate through collections using the Reset() and Next() method combinations. However, in most cases the foreach statement is the preferred method, thus the most frequently used iterators can be converted to an enumerable type using the AsEnumerable() extension method, which allows these collections to now take advantage of LINQ.

The following is a short list of the interfaces that support enumerable types:

ESRI	ArcFM
ILongArray	IMMEnumField
IArray	IMMEnumTable
IEnumDomain	IMMEnumObjectClass
IEnumBSTR	IMMEnumFeederSource
IEnumIDs	IMMPxNodeHistory
IFields	IMMEnumPxTransition
IEnumRelationshipClass	IMMPxNode
IEnumFeatureClass	IMMEnumPxState
ICursor	IMMEnumPxTasks
IFeatureCursor	IMMEnumPxUser
ISet	IMMEnumPxFilter
...	There are many more that haven’t been listed for the sake of brevity.

These new extension methods allow you to write code like this:

int count = cursor.AsEnumerable().Count();

and:

var results =
    from x in cursor1.AsEnumerable()
    from y in cursor2.AsEnumerable()
    where x.get_Value(0) = y.get_Value(0)
    select new { Left = x, Right = y };

There are several objects (i.e. IEnumLayer, IMap, ID8List) in ArcFM and ArcGIS APIs that require recursion to obtain all of the data. In the past, you’d have to create a recursive method for iterating the contents of these hierarchical structures. These structures can now be traversed recursively using LINQ.

• Traversing the contents of the IMap.

var map = ArcMap.Application.GetActiveMap();
var layerDefinitions = map.Where(o => o.Visible)
                        .Select(o => (IFeatureLayerDefinition2) o)
foreach (var layerDefinition in layerDefinitions)
{
    layerDefinition.DefinitionExpression = null;
}

• Traversing the contents of the ID8List.

var map = ArcMap.Application.GetTargetTab();
var items = list.Where(o => o is IMMProposedObject)
                .Select(o => (IMMProposedObject) o.Value)
foreach (var item in items)
{
    IMMFieldManager fieldManager = item.FieldManager;
    IMMFieldAdapter fieldAdapter = fieldManager.FieldByName("TAG");
    fieldAdapter.Value = tag;
    item.Update(null);
}