How to freeze merged columns in data grid view when scrolling vertically? - vb.net

Question

I have a data grid view where I need the columns to be frozen or fixed when scrolling vertically.
I have a data grid view control in vb.net windows application which displays the data in a parent-child hierarchy(as shown below). The first column displays the parent data and the second column displays all its child data. The child data in the second column can be as much as 100 rows or even more. So when scrolling down through the grid, the value in the first column does not remain there as it is while the values in the second column(i.e. the child data) scrolls down. So if the user wants to check to which parent, the current child info belongs to, then again he will have to scroll up to the starting of the column to find the name of the parent. I want the values in the first column to be displayed or frozen till it reaches the end of the list of its child values in the grid or at least till the next row where the next parent data starts. I have suggested the client to go with a tree view but they are not agreeing and need it in a data grid view itself. Is there anyway to achieve this in a data grid view?
Thanks in advance.

Answer 1

You can't freeze a row (in runtime, on dgv scrolling) with index greater than zero because all those before are frozen and at that point you can't scroll your datagridview.
If I understood correctly what you want I wrote this class quickly (probably should be optimized). Usage is simple.
1 - First create your own datagridview.
2 - then add your columns and rows (IMPORTANT: Put a “X” in the Tag in each row is a Parent or is considered as title for other rows as you seen in TestPopulate method) .
3 - Call the class I made by passing the datagridview (you created first) as a parameter. At this point this control takes its size, placement and REPLACE YOUR DATAGRIDVIEW .
Private Class CustomDgv
Inherits Panel
Dim WithEvents TopDgv As DataGridView = New DataGridView
Dim WithEvents DownDgv As DataGridView = New DataGridView
Dim Cols As Integer
' This variable is in case you have more rows as "headrow"
' In TestPopulate you can see how to get those
Dim listOfOwnerRows As List(Of Integer) = New List(Of Integer)
Dim currentTopRow As Integer = -1
Protected Overloads Property Height As Integer
Get
Return MyBase.Height
End Get
Set(value As Integer)
MyBase.Height = value
TopDgv.Height = TopDgv.RowTemplate.Height - 1
DownDgv.Height = value - TopDgv.Height - 1
End Set
End Property
Protected Overloads Property Width As Integer
Get
Return MyBase.Width
End Get
Set(value As Integer)
MyBase.Width = value
TopDgv.Width = value - 1
DownDgv.Width = value - 1
End Set
End Property
Sub New(dgvOriginal As DataGridView)
DownDgv = dgvOriginal
Dim parentCtrl As Control = dgvOriginal.Parent
parentCtrl.Controls.Remove(dgvOriginal)
parentCtrl.Controls.Add(Me)
Me.Location = DownDgv.Location
Me.Size = DownDgv.Size
Me.BorderStyle = DownDgv.BorderStyle
TopDgv.Width = Width - 2 - SystemInformation.VerticalScrollBarWidth
TopDgv.Height = TopDgv.RowTemplate.Height
TopDgv.ScrollBars = ScrollBars.None
TopDgv.ColumnHeadersVisible = False
TopDgv.BorderStyle = BorderStyle.None
DownDgv.ColumnHeadersVisible = False
DownDgv.BorderStyle = BorderStyle.None
TopDgv.Left = 0
DownDgv.Left = 0
DownDgv.Width = Width - 2
DownDgv.Height = Height - 2
For Each Col As DataGridViewColumn In DownDgv.Columns
Dim cIndex As Integer = TopDgv.Columns.Add(Col.Clone)
If Col.Frozen Then
TopDgv.Columns(cIndex).Frozen = True
End If
Cols += 1
Next
DownDgv.Top = 0
Me.Controls.Add(TopDgv)
Me.Controls.Add(DownDgv)
If DownDgv.Rows.Count > 0 Then
listOfOwnerRows = (From R As DataGridViewRow In DownDgv.Rows
Where R.Tag = "X"
Select R.Index).ToList
If listOfOwnerRows.Count > 0 Then
SetFrosenRow(listOfOwnerRows(0))
End If
End If
End Sub
Protected Sub SetFrosenRow(index As Integer)
If DownDgv.Rows.Count > index Then
TopDgv.Rows.Clear()
TopDgv.Rows.Add()
Dim currentRIndex As Integer = DownDgv.FirstDisplayedScrollingRowIndex
'If you want onlly the base row
For i As Integer = 0 To Cols - 1
TopDgv.Rows(0).Cells(i).Value = DownDgv.Rows(index).Cells(i).Value
Next
'Or else get the diplayed on top row
TopDgv.Rows(0).DefaultCellStyle = New DataGridViewCellStyle With {
.BackColor = Color.Bisque
}
currentTopRow = index
End If
End Sub
Protected Sub SetChildValuesInTopRow(index As Integer)
For i As Integer = 1 To Cols - 1
TopDgv.Rows(0).Cells(i).Value = DownDgv.Rows(index).Cells(i).Value
Next
End Sub
Private Sub DownDgv_Scroll(sender As Object, e As ScrollEventArgs) Handles DownDgv.Scroll
Try
If e.ScrollOrientation = ScrollOrientation.VerticalScroll Then
Dim topR As Integer = DownDgv.FirstDisplayedScrollingRowIndex
'If you want in top row the current value that is in the top uncomment this
SetChildValuesInTopRow(topR)
If listOfOwnerRows.Count > 0 Then
Dim rToSetAsOwner As Integer = listOfOwnerRows(listOfOwnerRows.Count - 1)
For i As Integer = listOfOwnerRows.Count - 1 To 0 Step -1
If listOfOwnerRows(i) <= topR Then
rToSetAsOwner = listOfOwnerRows(i)
Exit For
End If
Next
If rToSetAsOwner <> currentTopRow Then
SetFrosenRow(rToSetAsOwner)
End If
Console.WriteLine("rToSetAsOwner: " & rToSetAsOwner)
End If
Else
TopDgv.HorizontalScrollingOffset = DownDgv.HorizontalScrollingOffset
End If
Catch ex As Exception
Console.WriteLine(ex.ToString)
End Try
End Sub
End Class
Usage:
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles Me.Load
Try
' first populate you grid putting a tag in each row which is a header/parent/title for other rows
TestPopulate()
Dim customControl As Control = New CustomDgv(DataGridView1)
Catch ex As Exception
Console.WriteLine(ex.ToString)
End Try
End Sub
Sub TestPopulate()
For i As Integer = 0 To 100
DataGridView1.Rows.Add()
If i = 0 Then
DataGridView1.Rows.Item(0).Cells(0).Value = "Owner 0"
DataGridView1.Rows(0).Tag = "X"
End If
If i = 50 Then
DataGridView1.Rows.Item(50).Cells(0).Value = "Owner 50"
DataGridView1.Rows(50).Tag = "X"
End If
If i = 70 Then
DataGridView1.Rows.Item(70).Cells(0).Value = "Owner 70"
DataGridView1.Rows(70).Tag = "X"
End If
DataGridView1.Rows.Item(i).Cells(1).Value = "child_" & i.ToString & "_1"
DataGridView1.Rows.Item(i).Cells(2).Value = "child_" & i.ToString & "_2"
Next
End Sub
I hope I have been helpful