Save and Restore the rows states when resetting.

Environment

Product Version	2018.1 220
Product	RadGridView for WinForms

Description

There are cases where you need to reset or rebind the grid which will reset the expanded rows and the position of the scrollbar.

Solution

This article shows how you can save/restore the sates and the scrollbar position.

1. First you need a class to store the state of each row.

struct State
{
    public bool Expanded { get; set; }

    public bool Selected { get; set; }

    public State(bool expanded, bool selected) : this()
    {
        this.Expanded = expanded;
        this.Selected = selected;
    }
}

Friend Structure State
    Public Property Expanded() As Boolean

    Public Property Selected() As Boolean

    Public Sub New(ByVal expanded As Boolean, ByVal selected As Boolean)
        Me.New()
        Me.Expanded = expanded
        Me.Selected = selected
    End Sub
End Structure

2. Now you can create the methods that will save and then restore the grid state:

Dictionary<object, State> nodeStates = new Dictionary<object, State>();
private void SaveExpandedStates(GridViewDataRowInfo rowToSave)
{
    if (rowToSave != null && rowToSave.DataBoundItem != null)
    {
        if (!nodeStates.ContainsKey(rowToSave.DataBoundItem))
        {
            nodeStates.Add(rowToSave.DataBoundItem, new State(rowToSave.IsExpanded, rowToSave.IsCurrent));
        }
        else
        {
            nodeStates[rowToSave.DataBoundItem] = new State(rowToSave.IsExpanded, rowToSave.IsCurrent);
        }
    }
    foreach (GridViewDataRowInfo childRow in rowToSave.ChildRows)
    {
        SaveExpandedStates(childRow);
    }
}

private void RestoreExpandedStates(GridViewDataRowInfo rowToRestore)
{
    if (rowToRestore != null && rowToRestore.DataBoundItem != null &&
        nodeStates.ContainsKey(rowToRestore.DataBoundItem))
    {
        rowToRestore.IsExpanded = nodeStates[rowToRestore.DataBoundItem].Expanded;
        rowToRestore.IsCurrent = nodeStates[rowToRestore.DataBoundItem].Selected;
        rowToRestore.IsSelected = nodeStates[rowToRestore.DataBoundItem].Selected;
    }

    foreach (GridViewDataRowInfo childRow in rowToRestore.ChildRows)
    {
        RestoreExpandedStates(childRow);
    }
}

Private nodeStates As New Dictionary(Of Object, State)()
Private Sub SaveExpandedStates(ByVal rowToSave As GridViewDataRowInfo)
    If rowToSave IsNot Nothing AndAlso rowToSave.DataBoundItem IsNot Nothing Then
        If Not nodeStates.ContainsKey(rowToSave.DataBoundItem) Then
            nodeStates.Add(rowToSave.DataBoundItem, New State(rowToSave.IsExpanded, rowToSave.IsCurrent))
        Else
            nodeStates(rowToSave.DataBoundItem) = New State(rowToSave.IsExpanded, rowToSave.IsCurrent)
        End If
    End If
    For Each childRow As GridViewDataRowInfo In rowToSave.ChildRows
        SaveExpandedStates(childRow)
    Next childRow
End Sub

Private Sub RestoreExpandedStates(ByVal rowToRestore As GridViewDataRowInfo)
    If rowToRestore IsNot Nothing AndAlso rowToRestore.DataBoundItem IsNot Nothing AndAlso nodeStates.ContainsKey(rowToRestore.DataBoundItem) Then
        rowToRestore.IsExpanded = nodeStates(rowToRestore.DataBoundItem).Expanded
        rowToRestore.IsCurrent = nodeStates(rowToRestore.DataBoundItem).Selected
        rowToRestore.IsSelected = nodeStates(rowToRestore.DataBoundItem).Selected
    End If

    For Each childRow As GridViewDataRowInfo In rowToRestore.ChildRows
        RestoreExpandedStates(childRow)
    Next childRow
End Sub

3. The final step is to use the above methods, this snippet show how restore the scrollbar position as well:

private void RadButton1_Click(object sender, EventArgs e)
{
    int scrollBarValue = radGridView1.TableElement.VScrollBar.Value;
    foreach (GridViewDataRowInfo rowToSave in radGridView1.Rows)
    {
        SaveExpandedStates(rowToSave);
    }


    radGridView1.DataSource = null;
    radGridView1.DataSource = master;


    foreach (GridViewDataRowInfo rowToRestore in radGridView1.Rows)
    {
        RestoreExpandedStates(rowToRestore);
    }

    radGridView1.TableElement.VScrollBar.Value = scrollBarValue;

}

Private Sub RadButton1_Click(ByVal sender As Object, ByVal e As EventArgs)
    Dim scrollBarValue As Integer = radGridView1.TableElement.VScrollBar.Value
    For Each rowToSave As GridViewDataRowInfo In radGridView1.Rows
        SaveExpandedStates(rowToSave)
    Next rowToSave


    radGridView1.DataSource = Nothing
    radGridView1.DataSource = master


    For Each rowToRestore As GridViewDataRowInfo In radGridView1.Rows
        RestoreExpandedStates(rowToRestore)
    Next rowToRestore

    radGridView1.TableElement.VScrollBar.Value = scrollBarValue

End Sub