dynamic columns disappears after postback

问题:

I have a GridView with some BoundFields and two TemplateFields. In these two TemplateFields, I dynamically create UserControls containing a DropDownList and a TextBox, which users can modify.

When I try to get the values of the controls after a PostBack, the values in BoundFields are still there but my dynamic controls disappears. I can create them again but it won't get the user's values... How can I get these values before they're lost?

Here's some of my code:

In the RowDataBound event:

Select Case type
    Case "BooleanBis"
        e.Row.Cells(2).Controls.Clear()
        Dim list1 As BooleanBisList = New BooleanBisList(avant, False)
        e.Row.Cells(2).Controls.Add(list1)

        e.Row.Cells(4).Controls.Clear()
        Dim list2 As BooleanBisList = New BooleanBisList(apres, True)
        e.Row.Cells(4).Controls.Add(list2)
    Case "Boolean"
        e.Row.Cells(2).Controls.Clear()
        Dim list3 As BooleanList = New BooleanList(avant, False)
        e.Row.Cells(2).Controls.Add(list3)

        e.Row.Cells(4).Controls.Clear()
        Dim list4 As BooleanList = New BooleanList(apres, True)
        e.Row.Cells(4).Controls.Add(list4)
End Select

In my button click event, I try to get the user control :

Case "String"
    temp.ChampValeurApres = DirectCast(Tableau1.Rows(i).Cells(selectedColumn).Controls(1), TextBox).Text

but i get the error that it doesn't exist.

回答1:

You should create dynamic controls in RowCreated instead of RowDataBound because this event gets fired on every postback whereas RowDataBound only will fire when the GridView gets databound to it's DataSource.

Dynamically created controls must be recreated on every postback with the same ID as before, then they retain their values in the ViewState and events will fire correctly(f.e. a DropDownList's SelectedIndexChanged event).

So you should create them in RowCreated and "fill" them in RowDataBound(f.e. the DropDownList datasource/Items or a TextBox-Text).

回答2:

I had been using:

EnableViewState="false"

in the GridView attributes. Removing it solved my problem!