How to update one field of specific records using Entity Framework?

Question

I want update family of a person who his name is pejman. This is my object Class:

public class Person
{
    public int Id { get; set; }
    public string FirstNa         


        

Answer 1

assuming you have the instance of Person that the db can find (as mentioned by Paweł Bejger):

public class Person
    {
        /// 

        /// USAGE: await UpdateDbEntryAsync(myPerson, d => d.FirstName, d => d.LastName);
        /// 
        async Task UpdateDbEntryAsync(T entity, params Expression>[] properties) where T : class
        {
            try
            {
                var db = new RtTradeData.Models.ApplicationDbContext();
                var entry = db.Entry(entity);
                db.Set().Attach(entity);
                foreach (var property in properties)
                    entry.Property(property).IsModified = true;
                await db.SaveChangesAsync();
                return true;
            }
            catch (Exception ex)
            {
                System.Diagnostics.Debug.WriteLine("UpdateDbEntryAsync exception: " + ex.Message);
                return false;
            }
        }

        /// 

        /// The idea is that SomeFunction already has the instance of myPerson, that it wants to update.
        /// 
        public void SomeFunction()
        {
            myPerson.FirstName = "Another Name"; myPerson.LastName = "NewLastName";
            UpdateDbEntryAsync(myPerson, d => d.FirstName, d => d.LastName);
        }
        /// 

        /// Or directly requesting the person instance to update its own First and Last name...
        /// 
        public void Update(string firstName, string lastName)
        {
            FirstName = "Another Name"; LastName = "NewLastName";
            UpdateDbEntryAsync(this, d => d.FirstName, d => d.LastName);
        }

        Person myPerson = new Person { PersonId = 5, FirstName = "Name", LastName = "Family" };
        public int PersonId { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
    }

see as well update a single field in Entity Framework and Entity Framework update single