So, you mean using the same random color for the duplicate rows? For that, you need to group the rows by the cell values and use a color for each group. Doing this in the CellPainting event is a heavy task since it's being raised for each cell in the grid. Hence, I suggest adding a hidden DataColumn to the DataTable to keep the color index of each row. The indices are set when you bind the control the first time, and when the user modifies the values.
' +
Imports System.Reflection
Private colors As Color()
Private bmp As Bitmap
Sub New()
InitializeComponent()
' To reduce the flickering...
DataGridView1.GetType().
GetProperty("DoubleBuffered",
BindingFlags.Instance Or BindingFlags.NonPublic).
SetValue(DataGridView1, True)
End Sub
Protected Overrides Sub OnLoad(e As EventArgs)
MyBase.OnLoad(e)
' Collect dark colors...
colors = GetType(Color).
GetProperties(BindingFlags.Public Or BindingFlags.Static).
Where(Function(pi) pi.PropertyType = GetType(Color)).
Select(Function(pi) CType(pi.GetValue(GetType(Color), Nothing), Color)).
Where(Function(c)
Return ((
c.R * 0.299F +
c.G * 0.587F +
c.B * 0.114F) / 256.0F) <= 0.5F
End Function).ToArray()
bmp = My.Resources.Money
Dim Table1 = New DataTable("TableName")
Table1.Columns.AddRange({
New DataColumn("Column1", GetType(String)),
New DataColumn("Column2", GetType(Integer)),
New DataColumn("Column3", GetType(Integer)),
New DataColumn("ColorIndex", GetType(Integer))
})
Table1.Rows.Add("Item1", 44, 99)
Table1.Rows.Add("Item2", 50, 70)
Table1.Rows.Add("Item3", 75, 85)
Table1.Rows.Add("Item2", 60, 70)
Table1.Rows.Add("Item3", 75, 85)
Table1.Rows.Add("Item4", 77, 21)
Table1.Rows.Add("Item2", 50, 70)
' ...etc.
DataGridView1.DataSource = Table1
DataGridView1.Columns("ColorIndex").Visible = False
UpdateColorColumn()
Table1.AcceptChanges()
End Sub
Protected Overrides Sub OnFormClosed(e As FormClosedEventArgs)
MyBase.OnFormClosed(e)
bmp.Dispose()
DirectCast(DataGridView1.DataSource, IDisposable)?.Dispose()
End Sub
Private Sub DataGridView1_CellValueChanged(sender As Object,
e As DataGridViewCellEventArgs) _
Handles DataGridView1.CellValueChanged
UpdateColorColumn()
End Sub
Private Sub DataGridView1_CellPainting(sender As Object,
e As DataGridViewCellPaintingEventArgs) _
Handles DataGridView1.CellPainting
If e.RowIndex >= 0 AndAlso e.ColumnIndex = -1 AndAlso
e.RowIndex <> DataGridView1.NewRowIndex Then
Dim ellipseSize = DataGridView1.RowTemplate.Height - 3
Dim ellipseRect = New Rectangle(
e.CellBounds.X + (e.CellBounds.Width - ellipseSize) \ 2,
e.CellBounds.Y + (e.CellBounds.Height - ellipseSize) \ 2,
ellipseSize, ellipseSize)
Dim imgSize = ellipseSize ' Or smaller...
Dim imgRect = New Rectangle(
ellipseRect.X + (ellipseRect.Width - imgSize) \ 2,
ellipseRect.Y + (ellipseRect.Height - imgSize) \ 2,
imgSize, imgSize)
Dim drv = DirectCast(DataGridView1.Rows(e.RowIndex).DataBoundItem, DataRowView)
Dim colorIndex = Convert.ToInt32(drv.Item("ColorIndex"))
Dim g = e.Graphics
Dim gs = g.Save()
e.Paint(e.ClipBounds, DataGridViewPaintParts.Background Or
DataGridViewPaintParts.Border Or
DataGridViewPaintParts.SelectionBackground)
Using ellipseBrush = New SolidBrush(colors(colorIndex))
g.SmoothingMode = SmoothingMode.AntiAlias
g.FillEllipse(ellipseBrush, ellipseRect)
g.InterpolationMode = InterpolationMode.HighQualityBicubic
g.DrawImage(bmp, imgRect, 0, 0, bmp.Width, bmp.Height,
GraphicsUnit.Pixel)
End Using
g.Restore(gs)
e.Handled = True
End If
End Sub
Private Sub UpdateColorColumn()
Dim dt = DirectCast(DataGridView1.DataSource, DataTable)
dt.EndInit()
Dim groups = dt.AsEnumerable().
GroupBy(Function(g) New With {
Key .Col1 = g.Item(0),
Key .Col2 = g.Item(1),
Key .Col3 = g.Item(2) ' Remove this to group by the first two.
})
For i = 0 To groups.Count - 1
Dim group = groups(i)
Dim colorIndex = i Mod colors.Length
For Each row In group
row("ColorIndex") = colorIndex
Next
Next
End Sub
If you have a DataBase, fill the DataTable before you add the ColorIndex column. To update the DB, you don't need to do anything special regarding the additional column(s). The INSERT and UPDATE commands execute their SQL CommandText queries and ignore anything else in the Columns collection. However, you can get a copy of the current DataTable and exclude the non-database columns.
For example:
Dim dt = Table1.DefaultView.
ToTable(False, Table1.Columns.
Cast(Of DataColumn).
Where(Function(c) c.ColumnName <> "ColorIndex").
Select(Function(c) c.ColumnName).ToArray())
As another option, use the DataGridViewRow.Tag property to keep the color index. The same could have been written like this.
Private colors As Color()
' ...
Protected Overrides Sub OnLoad(e As EventArgs)
MyBase.OnLoad(e)
' ...
DataGridView1.DataSource = Table1
UpdateColorIndices()
End Sub
' ...
Private Sub DataGridView1_CellPainting(sender As Object,
e As DataGridViewCellPaintingEventArgs) _
Handles DataGridView1.CellPainting
If e.RowIndex >= 0 AndAlso e.ColumnIndex = -1 AndAlso
e.RowIndex <> DataGridView1.NewRowIndex Then
Dim ellipseSize = DataGridView1.RowTemplate.Height - 3
Dim ellipseRect = New Rectangle(
e.CellBounds.X + (e.CellBounds.Width - ellipseSize) \ 2,
e.CellBounds.Y + (e.CellBounds.Height - ellipseSize) \ 2,
ellipseSize, ellipseSize)
Dim imgSize = ellipseSize
Dim imgRect = New Rectangle(
ellipseRect.X + (ellipseRect.Width - imgSize) \ 2,
ellipseRect.Y + (ellipseRect.Height - imgSize) \ 2,
imgSize, imgSize)
Dim colorIndex = Convert.ToInt32(DataGridView1.Rows(e.RowIndex).Tag)
Dim g = e.Graphics
Dim gs = g.Save()
e.Paint(e.ClipBounds, DataGridViewPaintParts.Background Or
DataGridViewPaintParts.Border Or
DataGridViewPaintParts.SelectionBackground)
Using ellipseBrush = New SolidBrush(colors(colorIndex))
g.SmoothingMode = SmoothingMode.AntiAlias
g.FillEllipse(ellipseBrush, ellipseRect)
g.InterpolationMode = InterpolationMode.HighQualityBicubic
g.DrawImage(bmp, imgRect, 0, 0, bmp.Width, bmp.Height,
GraphicsUnit.Pixel)
End Using
g.Restore(gs)
e.Handled = True
End If
End Sub
Private Sub UpdateColorIndices()
DataGridView1.EndEdit()
Dim groups = DataGridView1.Rows.Cast(Of DataGridViewRow).
Where(Function(r) r.Index <> DataGridView1.NewRowIndex).
GroupBy(Function(r) New With {
Key .Col0 = r.Cells(0).Value,
Key .Col1 = r.Cells(1).Value,
Key .Col2 = r.Cells(2).Value
})
For i = 0 To groups.Count - 1
Dim index = i Mod colors.Length
For Each row In groups(i)
row.Tag = index
Next
Next
DataGridView1.Invalidate()
End Sub
Also, you could create a Dictionay(Of Integer, Color) where each KeyValuePair holds the row index and the ellipse color.
Private colors As Color()
Private ReadOnly dictColors As New Dictionary(Of Integer, Color)
' ...
Private Sub DataGridView1_CellPainting(sender As Object,
e As DataGridViewCellPaintingEventArgs) _
Handles DataGridView1.CellPainting
If e.RowIndex >= 0 AndAlso e.ColumnIndex = -1 AndAlso
e.RowIndex <> DataGridView1.NewRowIndex Then
Dim ellipseSize = DataGridView1.RowTemplate.Height - 3
Dim ellipseRect = New Rectangle(
e.CellBounds.X + (e.CellBounds.Width - ellipseSize) \ 2,
e.CellBounds.Y + (e.CellBounds.Height - ellipseSize) \ 2,
ellipseSize, ellipseSize)
Dim imgSize = ellipseSize
Dim imgRect = New Rectangle(
ellipseRect.X + (ellipseRect.Width - imgSize) \ 2,
ellipseRect.Y + (ellipseRect.Height - imgSize) \ 2,
imgSize, imgSize)
Dim g = e.Graphics
Dim gs = g.Save()
e.Paint(e.ClipBounds, DataGridViewPaintParts.Background Or
DataGridViewPaintParts.Border Or
DataGridViewPaintParts.SelectionBackground)
Using ellipseBrush = New SolidBrush(dictColors(e.RowIndex))
g.SmoothingMode = SmoothingMode.AntiAlias
g.FillEllipse(ellipseBrush, ellipseRect)
g.InterpolationMode = InterpolationMode.HighQualityBicubic
g.DrawImage(bmp, imgRect, 0, 0, bmp.Width, bmp.Height,
GraphicsUnit.Pixel)
End Using
g.Restore(gs)
e.Handled = True
End If
End Sub
Private Sub UpdateColorIndices()
DataGridView1.EndEdit()
dictColors.Clear()
Dim groups = DataGridView1.Rows.Cast(Of DataGridViewRow).
Where(Function(r) r.Index <> DataGridView1.NewRowIndex).
GroupBy(Function(r) New With {
Key .Col0 = r.Cells(0).Value,
Key .Col1 = r.Cells(1).Value,
Key .Col2 = r.Cells(2).Value
})
For i = 0 To groups.Count - 1
Dim index = i Mod colors.Length
For Each row In groups(i)
dictColors(row.Index) = colors(index)
Next
Next
DataGridView1.Invalidate()
End Sub
