Gridview control: Using DataKeys or other methods to get data from cells. (Using C#)

I am currently working on a personal project where I have a gridview. I need to get a value from a cell. But, it is a Notes field that could have up to 150 characters.  I can use a DataKey. But, does that use more memory in the long run? My project is very small. What about in the real world? Would this be an issue? I have seen examples where people have used the row indexes. (I have yet to get one to work.) From reading the MSDN page on DataKeys, it seems like they should be used for primary key values for a row. In my project, the Notes column is not a primary key for this data row. It may not even contain anything as it is not required when data is set up/saved.