SPSite objSite = new SPSite("http://sharepointsvr:123/");
SPWeb objWeb = objSite.RootWeb;
SPFolder oFolder = objWeb.GetFolder("Participant");
SPFileCollection collFiles = oFolder.Files;
objWeb.AllowUnsafeUpdates = true;
foreach (SPFile oFile in collFiles.Folder.Files)
{
SPListItem oListItem = oFile.Item;
oListItem.File.CheckOut();
oListItem["ProgramaticField"] = "Chanaka has done it";
oListItem.SystemUpdate();
oListItem.File.CheckIn("chana did");
}
NB:-
(1) We Cant use this method under "SPSecurity.RunWithElevatedPrivileges(delegate.."
(2) If we want to edit a field that is filling from infopath form we have to use
oListItem["Fld_x0020_Other_x0020_Names"] instead of oListItem["ProgramaticField"]