Here I am going to explain how to get list of filtered columns including filter value from code behind in telerik radgrid.
The below tutorial helps us to get list of filtered values from telerik radgrid. For reports we are able to save the filtered values in database and also we can apply when next time we opening the report grid. For get list of group columns click here get list of group columns.

string filterXml = "<Filters><Filter><ColumnName>FirstName</ColumnName>
<Vlaues>Dhina,Venkatesh</Vlaues></Filter></Filters>";
filterXml = filterXml.TrimStart('"').TrimEnd('"');
if (filterXml != "" && filterXml != null)
{
XDocument oXDoc = XDocument.Parse(filterXml);
var FilterDetails = from x in oXDoc.Root.Descendants("Filters").Descendants("Filter") select x;
if (FilterDetails.Count() > 0)
{
foreach (var item in FilterDetails)
{
string FilterData = item.ToString();
XDocument oXDocFilter = XDocument.Parse(FilterData);
string ColumnName = XmlReConversionFromat(oXDocFilter.Root.Element("ColumnName").Value.ToString());
string Values = XmlReConversionFromat(oXDocFilter.Root.Element("Values").Value.ToString());
if (boundColumn.DataField.ToLower() == ColumnName.ToLower())
{
boundColumn.ListOfFilterValues = Values.Split(',');
}
}
}
}