Maintaining Selection with Expand Collapse

[Adam]

We are using the latest service pack of the Q3 2008 RadGrid. My grid has 2 levels of hierarchy, the first level is just a list of people's names and the second level is detailed information about their order.

Below is the NeedDataSource function. DataSourcePeople is a datatable stored in viewstate.

Private Sub grdPerson_NeedDataSource(ByVal source As Object, ByVal e As Telerik.Web.UI.GridNeedDataSourceEventArgs) Handles grdPerson.NeedDataSource
        grdPerson.DataSource = DataSourcePeople
    End Sub

When the grid runs it's PreRender event, it runs the following code. This is used to look in the DataSource (another datatable with their order information) to see if the row has been previously selected so that we can reselect the items after paging, sorting, etc.

Private Sub grdPerson_PreRender(ByVal sender As Object, ByVal e As System.EventArgs) Handles grdPerson.PreRender
        For Each item As Telerik.Web.UI.GridItem In grdPerson.MasterTableView.ItemsHierarchy
            If item.OwnerTableView.Name = "Detail" Then
                If DataSource.Select("ResourceID = '" & item.OwnerTableView.DataKeyValues(item.ItemIndex).Item("ResourceID") & "' AND PersonID = '" & item.OwnerTableView.DataKeyValues(item.ItemIndex).Item("PersonID") & "'").Length > 0 Then
                    If DataSource.Select("ResourceID = '" & item.OwnerTableView.DataKeyValues(item.ItemIndex).Item("ResourceID") & "' AND PersonID = '" & item.OwnerTableView.DataKeyValues(item.ItemIndex).Item("PersonID") & "'")(0)("Selected") = True Then
                        item.Selected = True
                    Else
                        item.Selected = False
                    End If
                End If
            End If
        Next
    End Sub

When a user expands a person to see their orders the following code is run in the DetailTableDataBind event. The ExpandPerson function simply finds all of the person's orders and adds them to the DataSource data table so that it can be bound.

Dim dataitem As Telerik.Web.UI.GridDataItem = CType(e.DetailTableView.ParentItem, Telerik.Web.UI.GridDataItem)

        If DataSource.Select("PersonID = '" & dataitem.GetDataKeyValue("PersonID") & "'").Length = 0 Then
            ExpandPerson(dataitem.GetDataKeyValue("PersonID"))
        End If

        e.DetailTableView.DataSource = DataSource.Select("PersonID = '" & dataitem.GetDataKeyValue("PersonID") & "'", "Course ASC")

Finally, we have our event (the ItemCommand) to track what was changed in the detail table so that we can reselect them when the user expands the person again (assuming they do expand the person after collapsing them). This appears to be where the trouble begins.

Private Sub grdPerson_ItemCommand(ByVal source As Object, ByVal e As Telerik.Web.UI.GridCommandEventArgs) Handles grdPerson.ItemCommand
        If e.CommandName = "ExpandCollapse" Then
            For Each item As Telerik.Web.UI.GridItem In grdPerson.MasterTableView.ItemsHierarchy
                If item.Selected Then
                    If DataSource.Select("ResourceID = '" & item.OwnerTableView.DataKeyValues(item.ItemIndex).Item("ResourceID") & "' AND PersonID = '" & item.OwnerTableView.DataKeyValues(item.ItemIndex).Item("PersonID") & "'").Length > 0 Then
                        Dim dr As DataRow = DataSource.Select("ResourceID = '" & item.OwnerTableView.DataKeyValues(item.ItemIndex).Item("ResourceID") & "' AND PersonID = '" & item.OwnerTableView.DataKeyValues(item.ItemIndex).Item("PersonID") & "'")(0)
                        dr("Selected") = True
                        dr("Hours") = CType(item.FindControl("txtHours"), TextBox).Text
                        dr("Minutes") = CType(item.FindControl("txtMinutes"), TextBox).Text
                        dr("Score") = CType(item.FindControl("txtScore"), TextBox).Text
                        dr("CompletionDate") = CType(item.FindControl("txtCompletionDate"), TextBox).Text
                        dr("CompletionDeadline") = CType(item.FindControl("txtCompletionDeadline"), TextBox).Text
                    End If
                Else
                    If DataSource.Select("ResourceID = '" & item.OwnerTableView.DataKeyValues(item.ItemIndex).Item("ResourceID") & "' AND PersonID = '" & item.OwnerTableView.DataKeyValues(item.ItemIndex).Item("PersonID") & "'").Length > 0 Then
                        DataSource.Select("ResourceID = '" & item.OwnerTableView.DataKeyValues(item.ItemIndex).Item("ResourceID") & "' AND PersonID = '" & item.OwnerTableView.DataKeyValues(item.ItemIndex).Item("PersonID") & "'")(0)("Selected") = False
                    End If
                End If
            Next
        End If
    End Sub

The initial NeedDataSource to populate the people's names works just fine. When a user clicks on the button to expand the grid it runs the events in the following order:

1. ItemCommand (ExpandCollapse)
2. NeedDataSource
3. DetailTableDataBind
4. PreRender

When a user collapses the person after expanding them it runs the following events:

1. ItemCommand (ExpandCollapse)
2. PreRender

The problem occurs when I select something before collapsing. This causes it to run the following events:

1. ItemCommand (ExpandCollapse, it updates the DataSource data table with the correct values)
2. PreRender
3. NeedDataSource
4. DetailTableDataBind

Their are few problems with this. First, it doesn't collapse as it should. Second, even though it doesn't collapse it loses it's selection (since the PreRender event doesn't fire to reselect it). Other columns (for example Score, Hours, etc.) show with the values entered. Any idea why it would decide to run the NeedDataSource and DetailTableDataBind after updating the data. My first inclination was that it was doing this because it detected that it's data sources have changed and therefore it needed to rebind, however, just because it rebinds doesn't mean that it shouldn't still collapse as it's supposed to.

Any help would be greatly appreciated. The end goal is that I can have a grid that I can expand and collapse correctly and it would keep the items selected inside of the detail table when I would expand to view it again.

Thanks,

Adam

[Shinu]

Hi Adam,

Go through the following code library submission which demonstrates how to Retain expanded/selected state in hierarchy on rebind  and see whether it helps to some extent.

Retain expanded/selected state in hierarchy on rebind 



Shinu

[Adam]

I've looked over the code sample and I don't think that will apply to our situation. What I'm unsure of is why it calls the NeedDataSource and DetailTableDatabind after I select something in the child table, but it will expand and collapse just fine when I don't select an item. Does the RadGrid automatically attempt to rebind itself if it knows the datasource has changed? If it does, is there a way to tell it not to do that in these circumstances so that it would collapse like usual and then only rebind when I expand?