将数据从数据绑定列表框移到未绑定列表框并返回VB.NET [英] Moving Data From Databound Listbox To Unbound Listbox And Back VB.NET

问题描述

因此，我一直在浏览，并且有很多关于如何将数据从列表框移动到列表框的说明. 我有一个列表框绑定到我的SQL Server的源，而另一个未绑定.我的目标是将数据从第一个(LBsearch)移至第二个(LBselect)并移回.我见过有人说用 LBselect.Items.Add(LBsearch.SelectedItem)，但是它不返回数据，而是显示System.Data.DataRowView.我已经尝试了许多不同的后缀，并且除了LBsearch.text以外都显示了此后缀.然后从第一个删除数据，我一直在删除databindingsource (PersonBindingSource) PersonBindingSource.Remove(LBsearch.SelectedItem)，但是我的问题是再次添加数据.

So I have been browsing about and there are a lot of explanations on how to move data from listbox to listbox. I have a listbox bound to a source from my SQL server and another unbound. My aim is to move the data from the first (LBsearch) to the second (LBselect) and back. I have seen people say use LBselect.Items.Add(LBsearch.SelectedItem) however it doesn't return data and instead shows System.Data.DataRowView. I've tried many different suffixes and all show this apart from LBsearch.text. Then to remove the data from the first one I've been removing the databindingsource (PersonBindingSource) with PersonBindingSource.Remove(LBsearch.SelectedItem) but my issue is adding the data back again.

PersonBindingSource.Add(LBselect.SelectedItem)给出错误:

System.InvalidOperationException: Objects added to a BindingSource's list must all be of the same type.
   at System.Windows.Forms.BindingSource.Add(Object value)
   at Project_Program.Participants.btnremoveselect_Click(Object sender, EventArgs e) in E:\Documents\Visual Studio\Project Program\Project Program\Participants.vb:line 39

PersonBindingSource.Add(PersonBindingSource.Item(LBsearch.SelectedIndex)) 给出错误:

System.ArgumentException: Cannot add external objects to this list.
   at System.Data.DataView.System.Collections.IList.Add(Object value)
   at System.Windows.Forms.BindingSource.Add(Object value)
   at Project_Program.Participants.btnremoveselect_Click(Object sender, EventArgs e) in E:\Documents\Visual Studio\Project Program\Project Program\Participants.vb:line 38

任何帮助将不胜感激.谢谢

Any help would be appreciated. Thanks

Private Sub btnaddselect_Click(sender As Object, e As EventArgs) Handles btnaddselect.Click
    If LBsearch.Items.Count > 0 Then
        MsgBox(LBsearch.Text)
        ' PersonBindingSource.Remove(PersonBindingSource.Item(LBsearch.SelectedIndex))
        LBselect.Items.Add(LBsearch.Text)
        PersonBindingSource.Remove(LBsearch.SelectedItem)

        ' filter()
    End If
End Sub

Private Sub btnremoveselect_Click(sender As Object, e As EventArgs) Handles btnremoveselect.Click
    If LBselect.Items.Count > 0 Then
        Try
            'PersonBindingSource.Add(PersonBindingSource.Item(LBsearch.SelectedIndex))
            PersonBindingSource.Add(LBselect.SelectedItem)

            MsgBox(LBselect.SelectedItem.ToString())
            LBselect.Items.Remove(LBselect.SelectedItem)
        Catch ex As Exception
            TextBox1.Text = (ex.ToString)
        End Try
        'filter()
    End If
End Sub

推荐答案

移动行的一个主要问题是，由于它们是DataRow，因此它们在未绑定控件中不能很好地显示.如果您提取有用的名称(例如名称)，则必须重新创建DataRow，以将其返回到原始/绑定/源代码控件.

A major problem with moving rows is that since they are DataRows, they will not display well in the unbound control. If you pull out something useful like a name, you will have to recreate the DataRow to return it to the original/bound/source control.

这是一个问题，因为现在它是新行，因此DataAdpter可能会将其再次添加到数据库中！避免这种情况的一种方法是克隆表.另外，如果/当您将它们移回时，它们将显示在列表的底部，而不是它们的原始位置.

This is a problem because, now it is a new row, so a DataAdpter might add it to the database again! One way to avoid that is to clone the table. Also, if/when you move them back, they will appear at the bottom of the list and not in their original position.

有一种比复制表数据并将任何内容移动到任何地方更好的方法.

There is a better way than duplicating the table data and moving anything anywhere.

由于可以使用简单的布尔值来表示被选择的行为，因此可以对其进行编码，以使Selected控件显示在一个控件中，而未选中的控件则显示在另一个控件中.为此，需要一个新的Selected列.如果可能，请使用您的SQL添加一个:

Since the act of being selected can be represented with a simple Boolean, it can be coded so that the Selected ones show in one control, the unSelected ones in the other. For this, a new Selected column is needed. If possible, add one using your SQL:

' MS Access syntax 
Dim SQL = "SELECT a, b, c,..., False As Selected FROM tblFoo"

这将在您的数据表中创建所有初始化为False的值的新列.您也可以手动添加列.

This will create the new column in your datatable with all the values initialized to False. You can also add the column manually.

' form level vars
Private dvSource As DataView
Private dvDest As DataView
...
' set up:
' *** Add a column manually if you cant use SQL
dtSample.Columns.Add("Selected", GetType(Boolean))

' we need to loop and set the initial value for an added column
For Each r As DataRow In dtSample.Rows
    r("Selected") = False
Next
' *** end of code for adding col manually

' when the column is added from SQL, you will need:
dtSample.Columns("Selected").ReadOnly = False


' create Source DV as Selected = False
dvSource = New DataView(dtSample,"Selected=False", "",
                                DataViewRowState.CurrentRows)
' create Dest DV as Selected = True
dvDest = New DataView(dtSample, "Selected=True", "",
                                DataViewRowState.CurrentRows)
' assign DS
lbSource.DataSource = dvSource
lbSource.DisplayMember = "Name"
lbSource.ValueMember = "Id"

lbDest.DataSource = dvDest
lbDest.DisplayMember = "Name"
lbDest.ValueMember = "Id"

然后在点击事件中:

' select
CType(lbSource.SelectedItem, DataRowView).Row("Selected") = True

' deselect:
CType(lbSource.SelectedItem, DataRowView).Row("Selected") = False

两个DataView对象将在Selected上反过滤.当您更改行的状态时，它会立即从一个状态中删除，并在另一行中显示，而实际上并未从任何表(或集合或控件)中添加/删除.如果将其移回源，它将显示在与以前相同的位置.

The two DataView objects will filter on Selected inversely. When you change the state of a row, it is instantly removed from one and appears in the other without actually being added/removed from any table (or collection or control). If you move it back to the Source it will appear in the same position as before.

在这种情况下，任何移动的项目的RowState都将是Modified，当然是Modified(与移动到表的方法不同，它们将是新行(Added)，而不是).

In this case, the RowState of any item moved will be Modified, which of course it is (unlike the move-to-table approach where they would be new rows (Added) which they are not).

如果没有5或6张图片，很难说明，但是这个想法:

It is hard to illustrate without 5 or 6 images, but the idea:

实际上，这是一种非常简单的方法，比一个实际移动行的调用更经济.使用DataView s行/项看起来，它们将移至另一个表或控件，但它们并不需要，也不需要.

It is actually a pretty simple method and more economical than one invovling actually moving rows. Using DataViews the rows/items look like they move to another table or control, but they do not, nor do they need to.

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