Yes, it is possible but it is kind of a hack.
Step 1: Make your filter values pretty
For this, you'll need to create a class inheriting from SPGridView and override the
public class SPFilterGridView : SPGridView
protected override string GetCallbackResult()
string result = base.GetCallbackResult();
// do something to alter the result
// result = ...;
You'll need to debug to get it right but you should be able to clean up the list here.
Step 2: Fix your FilterExpression
After you make your filter values pretty, you'll notice that the filter won't work anymore. This will be due to your
FilterExpression trying to filter on the new "pretty" values instead of the ugly
String;#filterexp1 values which are the actual values.
You probably want to override
OnPreRender in your web part to dynamically fix your DataSource's FilterExpression:
protected override void OnPreRender(EventArgs e)
string fieldName = _grid.FilterFieldName;
// TODO: whatever logic to reformat FilterExpression (add String;# in there??)
_gridDS.FilterExpression = string.Format(format, value, fieldName);