arcgis 10.0 - Programmatically calculating the length of all polyline features in a featureclass

I've come across this issue a few times and have not yet found an agreed upon solution on any forum.

Simply put, I have a featureclass containing many polyline features. I would like to calculate the lengths of each feature and write that value to a new field, which I have already added to the featureclass.

I know that I can export the featureclass to a geodatabase and have the length calculated automatically, but that doesn't make much sense in terms of programmatic workflow. It seems like I might be missing something simple, but there are obviously others out there with the same unanswered question.

EDIT: I should have been more clear. I would like to carry this out using ArcObjects. The field calculator method that keeps coming up does not appear to work for this purpose.

EDIT 2: I've sorted out one method for doing this using ArcObjects. Solution/Code is below. Thanks for all the help and suggestions.

The following code assumes you are operating on IFeatureClass and have already added a field called "Length" to the existing FeatureClass (which contains a series of polyline Features). I have tested it on a shapefile containing about 300 polyline Features.

            Dim nLengthFieldIndex As Integer = pFCXS.FindField("Length")
            Debug.Assert(nLengthFieldIndex > -1)
            Dim dLength As Double
            If TypeOf pFC Is IFeatureClass Then
                Dim pFeatureCursor As IFeatureCursor
                pFeatureCursor = pFC.Search(Nothing, False)
                If TypeOf pFeatureCursor Is IFeatureCursor Then
                    Dim pFeature As IFeature = pFeatureCursor.NextFeature()
                    While pFeature IsNot Nothing

                        Dim pLine As IPolyline
                        pLine = pFeature.Shape
                        If TypeOf pLine Is IPolyline Then
                            dLength = pLine.Length
                            pFeature.Value(nLengthFieldIndex) = dLength
                            pFeature.Store()
                            pFeature = pFeatureCursor.NextFeature
                        End If
                    End While
                End If

                pFeatureCursor.Flush()
            End If

Answer

I've sorted it out using ArcObjects (VB). Feel free to critique/comment/improve.

The following code assumes you are operating on IFeatureClass and have already added a field called "Length" to the existing FeatureClass (which contains a series of polyline Features). I have tested it on a shapefile containing about 300 polyline Features.

                Dim nLengthFieldIndex As Integer = pFCXS.FindField("Length")
                Debug.Assert(nLengthFieldIndex > -1)
                Dim dLength As Double
                If TypeOf pFC Is IFeatureClass Then
                    Dim pFeatureCursor As IFeatureCursor

                    pFeatureCursor = pFC.Search(Nothing, False)
                    If TypeOf pFeatureCursor Is IFeatureCursor Then
                        Dim pFeature As IFeature = pFeatureCursor.NextFeature()
                        While pFeature IsNot Nothing
                            Dim pLine As IPolyline
                            pLine = pFeature.Shape
                            If TypeOf pLine Is IPolyline Then
                                dLength = pLine.Length
                                pFeature.Value(nLengthFieldIndex) = dLength
                                pFeature.Store()

                                pFeature = pFeatureCursor.NextFeature
                            End If
                        End While
                    End If
                    pFeatureCursor.Flush()
                End If