I want to check if required field in SharePoint list is filled with data or not? Which method or property should i use?
SharePoint will not do the validation if an item is added by code. It would be best to iterate through all the fields and if that field is not read only & required, check if it's value is null or not. I guess there is no built-in method how to do it. Your best bet would be something like this in an ItemAdding event receiver:
foreach (SPField f in properties.ListItem.Fields)
if (!f.ReadOnlyField && f.Required && properties.AfterProperties[f.InternalName] == null)
//cancel adding item