Set Item level permission in sharepoint through coding

Here is the way we can add item level permission for a user on an item,

SPRoleDefinition oUserRole;

SPRoleAssignment oUserRoleAssignment;

SPListItem itm;

SPSite site = null;

SPWeb web = null;

string siteUrl = Request.Url.ToString();

site = new SPSite(siteUrl);

web = site.OpenWeb();

SPGroup grp = web.Groups[groupname];

itm=web.Lists[“Shared Documents”].Items[0];

oUserRole = web.RoleDefinitions.GetByType(SPRoleType.Administrator);

oUserRoleAssignment = new SPRoleAssignment(loginName, emailId, userDisplayName, notes);//for user

or

oUserRoleAssignment = new SPRoleAssignment(grp);//for group

oUserRoleAssignment.RoleDefinitionBindings.Add(oUserRole);

itm.RoleAssignments.Add(oUserRoleAssignment);

web.AllowUnsafeUpdates = true;

itm.Update();

web.Update();

web.AllowUnsafeUpdates = false;

This is useful for setting item level permission via code.