FlagColumn Outlook Style

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Introduction

The DataGridViewFlagColumn inherits the existing System.Windows.Forms.DataGridViewImageColumn. It paints the backcolor and chooses the image depending on the value you give the cell. In this code, I use a Flag enumeration of four possible values:

Public Enum Flag As Integer
    Blank = 0
    Red = 1
    Blue = 2
    Yellow = 3
End Enum 

If you create more flag icons, you can extend this enumeration. There also is an ErrorIcon supplied: this icon will be drawn if the value of the cell does not match one of the enumeration values.

The code has two classes: DataGridViewFlagColumn with just one member:

Public NotInheritable Class DataGridViewFlagColumn
    Inherits DataGridViewImageColumn

    Public Sub New()
        Me.CellTemplate = New DataGridViewFlagCell
        ...
    End Sub

End Class

In the constructor, I assign the CellTemplate to the second class: DataGridViewFlagCell, which inherits from System.Windows.Forms.DataGridViewImageCell. This class has some basic methods and functions: it retrieves the right icon and the right backcolor, and the Paint method will use them to paint the cells.

This class also provides a different backcolor when the mouse enters/leaves the cell. Have fun!