Question

我想将最后搜索到的查询保存在全局变量中，当我在另一种方法中使用它时，它会说：

ObjectDisposedException未被用户代码处理：ObjectContext实例已被释放，不能再用于需要连接的操作。

IQueryable lastQry = null;

private void SearchMethod()
{
   using(var ctx = new entityContex())
   {
      var qry = ctx.Table1.Where(t=> t.Name.StartWith(txtName.Text)).Take(100);

      lastQry = qry;

      dgvResult.DataSource = qry.ToList();
   }
}

private void RefreshResult()
{
   using(var ctx = new entityContex())
   {
      if(lastQry != null)
      //here is the Error ! <<---------------->>
      dgvResult.DataSource = lastQry.ToList();
   }
}

Answer 1

一种方法是创建和存储运行查询的委托：

Func<entityContex, IQueryable</*Table1 type*/>> queryExecutor = null;

private void SearchMethod()
{
   using(var ctx = new entityContex())
   {
      queryExecutor = c => c.Table1.Where(t=> t.Name.StartWith(txtName.Text)).Take(100);

      var qry = queryExecutor(ctx);

      dgvResult.DataSource = qry.ToList();
   }
}

private void RefreshResult()
{
   using(var ctx = new entityContex())
   {
      if(queryExecutor != null)
      dgvResult.DataSource = queryExecutor(ctx).ToList();
   }
}

Answer 2

不是存储IQueryable，而是存储列表：

List<Table1> lastQry = null;

private void SearchMethod()
{
 using(var ctx = new entityContex())
 {
   var qry = 
     ctx.Table1
       .Where(t=> t.Name.StartWith(txtName.Text))
       .Take(100)
       .ToList(); // <--

   lastQry = qry;
   dgvResult.DataSource = qry;
 }
}

private void RefreshResult()
{
  using(var ctx = new entityContex())
  {
    if(lastQry != null)
      dgvResult.DataSource = lastQry;
  }
}

如何将IQueryable对象重新附加到Context对象的新实例

2 个答案: