使用EntityFramework更新记录时出错

Question

I Want To Update A Record But Program Catch This Error

An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key."

This Is My Codes

public bool Update(User item, HttpPostedFileBase avatar)
{
    var tran = ContextEntities.Database.BeginTransaction(IsolationLevel.ReadUncommitted);
    try
    {
        var user = new UserDa().Get(ContextEntities, item.Id);//get current user
        CheckConstraint(item, Enums.Status.Update);
        //avatar checker
        if (avatar != null)
        {
            if (avatar.ContentType != "image/jpeg")
                throw new Exception("[Only Jpg Is Allowed");

            if (user.AvatarId == null)
            {
                item.AvatarId = new FileDa().Insert(ContextEntities, avatar);
            }
            else if (user.AvatarId != null)
            {
                item.AvatarId = new FileDa().Update(ContextEntities, (Guid)user.AvatarId, avatar);
            }
        }
        //password checker
        item.Password = string.IsNullOrWhiteSpace(item.Password) ? user.Password : Utility.Hash.Md5(item.Password);
        ContextEntities.Entry(item).State = EntityState.Modified;
        if (!new UserDa().Update(ContextEntities, item))
            throw new Exception();
        tran.Commit();
        return true;
    }
    catch (Exception ex)
    {
        tran.Rollback();
        throw new Exception(ex.Message);
    }
}

And This Is My Update Method In UserDa Class

public bool Update(PortalEntities contextEntities, User item)
{
    var res =  contextEntities.SaveChanges() > 0;
    return res;
}

Why The Error Shown And How Can I Fix It ?

Answer 1

I believe that Igor is correct. To fix the issue, when the user already exist in the database then update the user properties and not the item properties. Remove the line of code "ContextEntities.Entry(item).State = EntityState.Modified;" and save the changes.

public bool Update(User item, HttpPostedFileBase avatar)
{
    var tran = ContextEntities.Database.BeginTransaction(IsolationLevel.ReadUncommitted);
    try
    {
        var user = new UserDa().Get(ContextEntities, item.Id);//get current user
        CheckConstraint(item, Enums.Status.Update);

        if(user == null)
        {
            //throw and error or do something else
        }}

        //avatar checker
        if (avatar != null)
        {
            if (avatar.ContentType != "image/jpeg")
                throw new Exception("[Only Jpg Is Allowed");

            if (user.AvatarId == null)
            {
                user.AvatarId = new FileDa().Insert(ContextEntities, avatar);
            }
            else if (user.AvatarId != null)
            {
                user.AvatarId = new FileDa().Update(ContextEntities, (Guid)user.AvatarId, avatar);
            }
        }
        //password checker
        user.Password = string.IsNullOrWhiteSpace(item.Password) ? user.Password : Utility.Hash.Md5(user.Password);
        //ContextEntities.Entry(item).State = EntityState.Modified;
        if (!new UserDa().Update(ContextEntities, user))
            throw new Exception();
        tran.Commit();
        return true;
    }
    catch (Exception ex)
    {
        tran.Rollback();
        throw new Exception(ex.Message);
    }
}