Question

在我的视图模型中，我正在执行以下操作。

public List<Order> Orders { get; set; }

public ViewModel()
{
  using (Context context = new Context())
    Orders = context.Orders
      .Include(order => order.Status).ToList();
}
Order test1 = Orders.First(item => item.Status != null);
Order test2 = Orders.First(item => item.Status != null && item.Status.Id == 1);

所以我已经包含了导航属性并将它们放在那里供将来使用。但是，如果我四处寻找并展开被观察的物体，我会发现状态实际上没有任何价值。它会产生以下错误。

'（test1.Status）.Orders'抛出了'System.ObjectDisposedException'类型的异常

现在，我的理解是，如果我忘记使用 Include（），这就是结果，因为实体超出了上下文的范围并被处理掉了。但是在这种情况下，他们不是，我为什么会被打磨。

连连呢？我错过了什么？

在我开玩笑之后，我不能停止，但是这种印象是包含状态是正确的，但反过来，它不包括引用回到原订单。我对如何接近它感到有点困惑......

Answer 1

此问题默认情况下context LazyLoadingEnabled=true有Include，因此Status不会为每个热切加载的using (Context context = new Context()){ context.Configuration.LazyLoadingEnabled = false; Orders = context.Orders .Include(order => order.Status).ToList(); }设置后向引用。您可以尝试关闭该上下文的延迟加载，并且您将看到后向引用也将被正确加载：

    import android.content.Intent;
    import android.os.Bundle;
    import android.support.design.widget.FloatingActionButton;
    import android.support.design.widget.Snackbar;
    import android.view.View;
    import android.support.design.widget.NavigationView;
    import android.support.v4.view.GravityCompat;
    import android.support.v4.widget.DrawerLayout;
    import android.support.v7.app.ActionBarDrawerToggle;
    import android.support.v7.app.AppCompatActivity;
    import android.support.v7.widget.Toolbar;
    import android.view.Menu;
    import android.view.MenuItem;

    public class MainActivity extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
                this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.setDrawerListener(toggle);
        toggle.syncState();

        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);
    }

    @Override
    public void onBackPressed() {
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        if (drawer.isDrawerOpen(GravityCompat.START)) {
            drawer.closeDrawer(GravityCompat.START);
        } else {
            super.onBackPressed();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @SuppressWarnings("StatementWithEmptyBody")
    @Override
    public boolean onNavigationItemSelected(MenuItem item) {
        // Handle navigation view item clicks here.
        int id = item.getItemId();

        if (id == R.id.nav_ingredients) {
            Intent intent = new Intent(getApplicationContext(),IngredientsActivity.class);
            startActivity(intent);

        } else if (id == R.id.nav_recepies) {

        } else if (id == R.id.nav_grocery_list) {

        } else if (id == R.id.nav_share) {

        } else if (id == R.id.nav_send) {

        }

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        drawer.closeDrawer(GravityCompat.START);
        return true;
    }
}

我刚做了一个简单的演示并确认它有效。

ObjectDisposedException尽管使用了* Include *

1 个答案: