Adding fields to raster attribute table

Question

I have a raster attribute table associated with an IMAGINE .img raster that I build and open with:

IGPUtilities utils = new GPUtilities();
IRasterDatasetEdit2 raster = (IRasterDatasetEdit2)
 utils->OpenRasterDatasetFromString(path);
raster.BuildAttributeTable();
ITable vat = (raster as IRasterBandCollection).Item(0).AttributeTable;

I need to add new column to the table and populate with values. However, calling AddField on the table throws "The method or operation is not implemented" exception.

IFieldEdit field = new FieldClass();
field.Type_2 = esriFieldType::esriFieldTypeString;
field.Name_2 = "Name";
vat.AddField(field as IField); // Throws

Is there a direct way how to modify the existing attribute table or do I have to create one on my own and assign it to the raster using IRasterDatasetEdit2::AlterAttributeTable()?

I'm using ArcObjects .NET SDK with ArcGIS 9.3.1.

Edited

Once again ArcMap behaves curiously: When I open the raster in ArcMap after my code failed to add the field, I can open the attribute table but the 'Add Field...' option is disabled. If I remove the raster and open it again, I can add fields from ArcMap and also my code works!

Everything works fine with GeoTiff images.

I do not think this is a locking issue since I'm releasing all COM instances (via System::Runtime::InteropServices::Marshal::ReleaseComObject())

• Kirk Kuykendall: Does arcmap allow you to manually add a field to an img based raster?
• Martin Gunia: Only when I remove the raster my tool created and open it again. That suggests that something isn't quite finished (my code ends with exception but I make sure I'm releasing the underlying COM instances).
• Kirk Kuykendall: Did you try calling IDataLayer2.Disconnect then IDataLayer2.Connect ? Also, interactively, did you try killing your ArcSOCp.exe process? Maybe it has a lock on the raster.
• Martin Gunia: @Kirk: Thanks. The result of my tool is not a layer, it is a newly created raster. After my tool finishes, only then I open it as a layer in ArcMap and have the 'Add Field...' option disabled. Removing and opening fixes the problem. This does not happen with GeoTIFF images so I can go around using those, I'm just being curious now why .img won't work normally :) If I understand right ArcSOCp.exe is related to ArcGIS10 background processing? I'm still using ArcGIS 9.3.
• Kirk Kuykendall: Did you try calling ReleaseInternals?

Answer 1

I am not an ArcObject users but basically it should not possible to add a field to a raster. Conceptually you can't, since a raster is a grid with one value in the cell. You can only clone the raster and change the value of each cell.

Hote it helps.

Y.

• Martin Gunia: I'm not trying to add fields to the raster but to its attribute table (that is a normal table having one row for each qnique value in the raster). It works for GeoTIFF rasters but not for IMAGINE rasters.