C# - Applying Styles To A GridView Matching Certain Criteria?

I have a GridView control (GridView1) on a page which is reading from a database. I already have a CSS style applied to the GridView and all I want to do is change the background image applied in the style depending on if a certain cell has data in it or not.

The way I'm trying to handle this change is updating the CSS class applied to each row through C#. I have the code below doing this:

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{
GridViewRow row = e.Row;
string s = row.Cells[7].Text;
if (s.Length > 0)
{
row.CssClass = "newRowBackground";........

It seems as if the top piece of code is always returning the string with a value greater than 0, but when I check the database the fields are all null (except for my test record of "Smith").

I'm probably doing something very simple that's wrong here, but I can't see what. Like I said, I'm still very new to this. One thing I have tried is changing the argument in the if statement to things like: if (s != null), if (s != "") and if (s == string.empty) all with no luck.