Select Data

C#

In the following code sample the filter is set to retrieve values for each feature in the database. Without adding a computed identifier to the select command’s property collection, the select command would return all of the property values for each feature in the database. In this example, the computed identifier contains a function expression that converts the DateTime value in the DateTimeProp property to a string and returns the string. So the select returns a set of DateTime strings.

The following namespaces are used:

• OSGeo.FDO.Commands
• OSGeo.FDO.Commands.Feature
• OSGeo.FDO.Expression
• OSGeo.FDO.Filter

Identifier className = new Identifier("FeatureClass");
ISelect select = conn.CreateCommand(CommandType.CommandType_Select) as ISelect;
select.FeatureClassName = className;
Filter filter = Filter.Parse("ID >= 0");
select.Filter = filter;
ComputedIdentifier computedId = Expression.Parse("(ToString(DateTimeProp) as computedId)") as ComputedIdentifier;
select.PropertyNames.Add(computedId);
IFeatureReader reader = select.Execute();
reader.Close();