An interesting issue came up today that, although it now looks simple, did not have an immediately obvious solution. Specifically, what if you want to set properties of individual columns of a GridView at run-time (via C# code) rather than at design time in the aspx code.
For example, let's say you want to set the DataFormatString property of a BoundField column. In short, it is a 2-part solution. First, you must positionally extract your column out of the GridView's Columns property while casting it to your desired type (in this case a BoundField). Second, after you have set the properties, do the databind. So if you have column that you want to format as currency, the code might look like this:
BoundField
priceField = grid.Columns[0] as BoundField;
priceField.DataFormatString = "{0:c}";
priceField.HtmlEncode = false;
grid.DataSource = list;
grid.DataBind();
Note that since you're manually doing the data binding this will preclude you from using the ObjectDataSource in this case (since that happens before your user code in the Page_Load event).
Taking this one step further, you could even add columns dynamically at run-time doing this:
BoundField
someField = new BoundField();
someField.DataField = "Price";
someField.DataFormatString = "{0:c}";
someField.HtmlEncode = false;
grid.Columns.Add(someField);
Note: One reason this might throw you off at first is that in the C# intellisense, BoundColumn comes up first and if you're not watching carefully you might try to use that instead of BoundField which will prevent you from compiling!