Question

我正在尝试从列表视图中删除所选项目。值存储在数据库中。我在sqlite中尝试过。如何删除数据库中存在的值并更新列表视图

  private void Button_Click_3(object sender, RoutedEventArgs e)
    {
        var dbpath = ApplicationData.Current.LocalFolder.Path + "/Mydb1.db";


        var con = new SQLiteAsyncConnection(dbpath);

       var stt=con.QueryAsync<list>("delete from list where list1='"+list_view.SelectedItem+"'");
       con.DeleteAsync(stt);

       update();

    }

    public async void update()
    {
        var dbpath = ApplicationData.Current.LocalFolder.Path + "/Mydb1.db";
        var con = new SQLiteAsyncConnection(dbpath);

        List<list> mylist = await con.QueryAsync<list>("select * from list");
        if (mylist.Count != 0)
        {
            list_view.ItemsSource = mylist;
            list_view.DisplayMemberPath = "list1";
        }

    }

这里list1是列名，列表是表名

我放置了一个断点并执行了代码。它显示了一个异常（无法删除任务`1：它没有PK）我认为PK是异常中的列名，一旦从sqlite类检查下面的代码，那里触发了异常

public int Delete (object objectToDelete)
    {
        var map = GetMapping (objectToDelete.GetType ());
        var pk = map.PK;
        if (pk == null) {
            throw new NotSupportedException ("Cannot delete " + map.TableName + ": it has no PK");
        }
        var q = string.Format ("delete from \"{0}\" where \"{1}\" = ?", map.TableName, pk.Name);
        return Execute (q, pk.GetValue (objectToDelete));
    }

Answer 1

更改您的SQL查询。在查询中分配（list_view.Selecteditem）时，数据库无法识别所选值，因为列表中的多个项目对selectitem语句很熟悉。因此，首先存储所选项目并将其传递给查询。

private async void Button_Click_3(object sender, RoutedEventArgs e)
    {
        var dbpath = ApplicationData.Current.LocalFolder.Path + "/Mydb1.db";

        var con = new SQLiteAsyncConnection(dbpath);
        if (list_view.SelectedItem != null)
        {
            list k = (list)list_view.SelectedItem;
           await con.QueryAsync<list>("delete from list where list1='" + k.list1 + "'");

            update();
        }
 public async void update()
    {
        var dbpath = ApplicationData.Current.LocalFolder.Path + "/Mydb1.db";
        var con = new SQLiteAsyncConnection(dbpath);

        list_view.ItemsSource = new List<list>();
        List<list> mylist = await con.QueryAsync<list>("select * from list");
        if (mylist.Count != 0)
        {
            list_view.ItemsSource = mylist;
            list_view.DisplayMemberPath = "list1";
        }

    }

无法从列表视图中删除所选项目（sqlite中的值）

1 个答案: