Patching in RavenDB

0_IndexDefinition.cs

public class PosItemProjection_ByCategoryId : AbstractIndexCreationTask<PosItemProjection>
{
	public PosItemProjection_ByCategoryId()
	{
		Map = items => from item in items select new { item.CategoryId  };

		Index(x => x.CategoryId, FieldIndexing.NotAnalyzed);
	}
}

1_BulkUpdate.cs

private void BulkUpdateItemsInCategory(string categoryId, string propertyToUpdate, string newValue)
{
	var query = "CategoryId:\"{0}\"".FormatWith(categoryId);

	_store.DatabaseCommands.UpdateByIndex("PosItemProjection/ByCategoryId",
		new IndexQuery { Query = query },
		new[]
		{
				new PatchRequest
						{
								Type = PatchCommandType.Set,
								Name = propertyToUpdate,
								Value = newValue
						}
		},
		allowStale: true);

}