EF代码优先方法中的数据刷新问题

Question

Hi Im developing an WPF application using Entity Framework Code first method and Generic Repository pattern. My problem is at the time WPF application is running when I do a change to the data in the data base, WPF application data not showing that modified latest data. it is keeping all the data in the cache and not getting synch with the database. I have to close my application and need to rerun it to get the modified data. How can i resolve this problem. please help

public class GenericRepository<TEntity> where TEntity : class
{
    internal RcerpDbContext Context;
    internal DbSet<TEntity> DbSet;

    public GenericRepository(RcerpDbContext context)
    {
        this.Context = context;
        this.DbSet = context.Set<TEntity>();
    }

    public virtual IEnumerable<TEntity> Get(
        Expression<Func<TEntity, bool>> filter = null,
        Func<IQueryable<TEntity>, IOrderedQueryable<TEntity>> orderBy = Null,
        string includeProperties = "")
    {
        IQueryable<TEntity> query = DbSet;

        if (filter != null)
        {
            query = query.Where(filter);
        }

        query = includeProperties.Split(new char[] {','}, StringSplitOptions.RemoveEmptyEntries).Aggregate(query, (current, includeProperty) => current.Include(includeProperty));

        if (orderBy != null)
        {
            return orderBy(query).ToList();
        }
        else
        {
            return query.ToList();
        }
    }

    public virtual TEntity GetById(object id)
    {
        return DbSet.Find(id);
    }

    public virtual void Insert(TEntity entity)
    {
        DbSet.Add(entity);
    }

    public virtual void Delete(object id)
    {
        TEntity entityToDelete = DbSet.Find(id);
        Delete(entityToDelete);
    }

    public virtual void Delete(TEntity entityToDelete)
    {
        if (Context.Entry(entityToDelete).State == EntityState.Detached)
        {
            DbSet.Attach(entityToDelete);
        }
        DbSet.Remove(entityToDelete);
    }

    public virtual void Update(TEntity entityToUpdate)
    {
        var entry = Context.Entry(entityToUpdate);
        var primaryKey = DbSet.Create().GetType().GetProperty("Id").GetValue(entityToUpdate);

        if (entry.State != EntityState.Detached) return;
        var set = Context.Set<TEntity>();
        var attachedEntity = set.Find(primaryKey);
        if (attachedEntity != null)
        {
            var attachedEntry = Context.Entry(attachedEntity);
            attachedEntry.CurrentValues.SetValues(entityToUpdate);
        }
        else
        {
            entry.State = EntityState.Modified;
        }
    }

}

Answer 1

You need to create a new DbContext once you know it is refreshed (or if you want to check if any data has changed).

Your repository should ask for a Func<RcerpDbContext> to be injected, so it can dispose of the current context, and create a new one using the Func<> , once it knows it needs reload collections of data from the database.

Otherwise if you only want to reload a single entity, you can use:

Context.Entry<T>(entity).Reload()

Also if you do not want EF to keep a local copy you can use

Context.Set<TEntity>.AsNoTracking()

which will force EF not to store any local copies. Beware, that if you change your entity, and try to call SaveChange() NOTHING will happen. You will manually have to tell EF which propertied have been updated.

EDIT 1

If you want to reload a whole set:

Context.Set<Car>().Local.ToList().ForEach( x=>
{
  Context.Entry(x).State = EntityState.Detached;
}

Although I would highly recommend either

1. Using a new Context and disposing of current one.
2. Using the AsNoTracking() modifier for your queries.