vb.net 如何在数据绑定组合框上选择值？
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How to select value on a databound combobox?
提问by Zolomon
I have a ComboBoxthat's been bound to a DataViewthat's taken a filled DataTable. This DataTablehas three columns. Before the DataViewis bound to the ComboBoxI add another column and set some values.
我有一个ComboBox被绑定到一个DataView被填充的DataTable. 这DataTable有三列。在DataView绑定到ComboBox我之前添加另一列并设置一些值。
Dim table As DataTable = _retrieve.GetAllVersionsTable()
table.Columns.Add("FirstRow", GetType(Boolean))
Dim row As DataRow = table.NewRow()
row("ID") = -1
row("SomeValue") = -1
row("SomeText") = "N/A"
row("FirstRow") = True 'Fort sorting...
Dim view As DataView = New DataView(table)
view.Sort = "FirstRow DESC, SomeText DESC"
table.Rows.InsertAt(row, 0)
comboBox.DataSource = view
comboBox.ValueMember = "ID"
comboBox.DisplayMember = "SomeText"
Later on, I retrieve the same data and create a new DataTableand bind it to a DataGridViewin another form. From this form I set a value for the identity column from selected row in the DataGridView.
稍后，我检索相同的数据并创建一个新数据并将其DataTable绑定到DataGridView另一种形式的 a。在这个表单中，我为DataGridView.
When I get back to the first form, with the ComboBox, I wish to select the ComboBoxrow that has the same value, that I set from the second form, tied to its ValueMemberproperty. I thought that SelectedValuewould work for this but it doesn't. What else can I do?
当我回到第一个表单时ComboBox，我希望选择ComboBox具有相同值的行，该行是我从第二个表单设置的，并绑定到它的ValueMember属性。我认为这SelectedValue可以解决这个问题，但事实并非如此。我还可以做些什么？
comboBox.SelectedValue = myIdentityValue
Since the rows are different I can't use SelectedItemeither. Is there a way I can select the appropriate row without having to loop over all existing rows?
由于行不同，我也不能使用SelectedItem。有没有一种方法可以选择适当的行而不必遍历所有现有行？
采纳答案by Meta-Knight
According to MSDN:
根据 MSDN：
SelectedValue: Gets or sets the value of the member property specified by the ValueMember property.
SelectedValue：获取或设置由 ValueMember 属性指定的成员属性的值。
So according to documentation, doing something like this should work, assuming 123 is an ID present in the combobox, because ID has been set as the ValueMember:
所以根据文档，做这样的事情应该可以工作，假设 123 是组合框中存在的 ID，因为 ID 已设置为 ValueMember：
comboBox.SelectedValue = 123
If you can't get it to work (maybe binding with DataView doesn't work well?), then you could use SelectedIndex which always works.
如果你不能让它工作（也许与 DataView 绑定不能很好地工作？），那么你可以使用始终有效的 SelectedIndex 。
回答by Delcon
For anybody that comes across this topic, has the same problems like Zolom or me. I think I found a important thing that is not documented:
对于遇到此主题的任何人，都会遇到与 Zolom 或我一样的问题。我想我发现了一个没有记录的重要事情：
You must pass the same datatype to .SelectedValue. If not the search will fail without any hint.
您必须将相同的数据类型传递给 .SelectedValue。如果不是，搜索将在没有任何提示的情况下失败。
Let's say you fill your DataSource with with a database and have lets say integer as value-field you have to pass an integer to the SelectedIndex. If it was string you pass a string.
假设你用一个数据库填充你的数据源，并让整数作为值字段，你必须将一个整数传递给 SelectedIndex。如果它是字符串，则传递一个字符串。
I hope this helps...
我希望这有帮助...
回答by Fernando Rios
That issue you can solve setting to Nothingthe property datasource before than set the datasource:
在设置数据源之前，您可以解决将属性数据源设置为Nothing的问题：
Combobox.datasource=nothing
Combobox.DisplayMember="Data";
Combobox.ValueMember="ID";
Combobox.datasource = NewDataTable;
Combobox.SelectedValue = 4;
回答by shong
Use Combobox.text="". It will automatically change the selectedvalue property to your your entered text.
使用Combobox.text="". 它会自动将 selectedvalue 属性更改为您输入的文本。
