A class to print and print preview a DataGrid control

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Introduction

The System.Windows.Forms.DataGrid control is one of the most powerful and frequently used controls in the .NET arsenal and this class (DataGridPrinter) adds functionality to allow you to generate print and print previews from your data grid in a tidy and customizable layout.

To draw a grid, first draw a square

The basic operation when drawing a data grid is to draw a rectangle and fit text inside it. To do this I have a single subroutine called DrawCellString which draws a string inside a cell according to the alignment and format parameters passed in.

Public Function DrawCellString(ByVal s As String, _
      ByVal HorizontalAlignment As CellTextHorizontalAlignment, _
      ByVal VerticalAlignment As CellTextVerticalAlignment, _
      ByVal BoundingRect As Rectangle, _
      ByVal DrawRectangle As Boolean, _
      ByVal Target As Graphics, _
      ByVal PrintFont As Font)


        Dim x As Single, y As Single

        If DrawRectangle Then
            Target.DrawRectangle(_GridPen, BoundingRect)
        End If

        '\\ Set the text alignment

        If HorizontalAlignment = 
              CellTextHorizontalAlignment.LeftAlign Then
            _Textlayout.Alignment = StringAlignment.Near
        ElseIf HorizontalAlignment = 
                   CellTextHorizontalAlignment.RightAlign _
        Then
             _Textlayout.Alignment = StringAlignment.Far
        Else
             _Textlayout.Alignment = StringAlignment.Center
        End If

        Dim BoundingRectF As New RectangleF(BoundingRect.X + _CellGutter, _ 
                                BoundingRect.Y + _CellGutter,  _ 
                                BoundingRect.Width - (2 * _CellGutter),  _ 
                                BoundingRect.Height - (2 * _CellGutter))

        Target.DrawString(s, PrintFont, System.Drawing.Brushes.Black, _ 
                          BoundingRectF, _Textlayout)

End Function

There are two class level variables that are used to define how a cell is drawn: CellGutter specifies a margin (in pixels) between the edge of the string bounding box and the GridPen is the pen used to draw the box.

Now you can draw a box, you can draw a row

There are two types of rows you need to print in order to print a grid: a row of column headers and a row of data. This class always starts each new page with a row of column headers.

    Private Sub PrintGridHeaderLine(ByVal e As _
              System.Drawing.Printing.PrintPageEventArgs)

        Dim Top As Double = _PageContentRectangle.Top
        Dim Bottom As Double = Top + _Rowheight + (2 * _CellGutter)

        Top = RoundTo(Top, 2)
        Bottom = RoundTo(Bottom, 2)

        Dim nColumn As Integer

        For nColumn = 0 To GridColumnCount() - 1
            Dim rcCell As New Rectangle(_ColumnBounds(nColumn).Left, Top, _
                                 _ColumnBounds(nColumn).Width, Bottom - Top)
            Call DrawCellString(GetColumnHeadingText(nColumn),  _ 
                                CellTextHorizontalAlignment.CentreAlign, _
                                CellTextVerticalAlignment.MiddleAlign, _ 
                                rcCell, True, e.Graphics, _PrintFont)
        Next
    End Sub

This is fairly straightforward. The only tricky bit is getting the title of the column from the data grid which is done thus:

    Private Function GetColumnHeadingText(ByVal Column As Integer) As String

        If TypeOf _DataGrid.DataSource Is DataTable Then
            Return CType(_DataGrid.DataSource, _
                        DataTable).Columns(Column).ToString
        ElseIf TypeOf _DataGrid.DataSource Is DataSet Then
            Return CType(_DataGrid.DataSource, DataSet).Tables( _
                      _DataGrid.DataMember).Columns(Column).ToString
        ElseIf TypeOf _DataGrid.DataSource Is DataView Then
            Return CType(_DataGrid.DataSource, _
                    DataView).Table.Columns(Column).ToString
        Else
            'TODO : Get the column caption....

        End If
    End Function

And to print a row of data we do the same thing but with the row content of the current row:

Private Sub PrintGridLine(ByVal e As _
         System.Drawing.Printing.PrintPageEventArgs, _ 
              ByVal RowNumber As Integer)

        Dim RowFromTop As Integer = RowNumber + 1 - _CurrentPrintGridLine
        Dim Top As Double = _PageContentRectangle.Top + (RowFromTop * _
                                         ((_CellGutter * 2) + _Rowheight))
        Dim Bottom As Double = Top + _Rowheight + (2 * _CellGutter)

        Top = RoundTo(Top, 2)
        Bottom = RoundTo(Bottom, 2)

        Dim Items() As Object

            If TypeOf _DataGrid.DataSource Is DataTable Then
                Items = CType(_DataGrid.DataSource, _
                        System.Data.DataTable).DefaultView.Item(_
                                         RowNumber - 1).Row.ItemArray
            ElseIf TypeOf _DataGrid.DataSource Is DataSet Then
                Items = CType(_DataGrid.DataSource, _
                              System.Data.DataSet).Tables(     _
                                _DataGrid.DataMember).DefaultView.Item(_
                                             RowNumber - 1).Row.ItemArray
            ElseIf TypeOf _DataGrid.DataSource Is DataView Then
                Items = CType(_DataGrid.DataSource, _
                         System.Data.DataView).Table.DefaultView.Item( _
                                             RowNumber - 1).Row.ItemArray
            Else
                'TODO : Get the content for the current row from the data 

                '       source ....

            End If

            Dim nColumn As Integer
            For nColumn = 0 To Items.Length - 1
                Dim rcCell As New Rectangle(_ColumnBounds(nColumn).Left, Top,_
                       _ColumnBounds(nColumn).Width, Bottom - Top)
                Call DrawCellString(Items(nColumn).ToString, _ 
                               CellTextHorizontalAlignment.CentreAlign, _ 
                               CellTextVerticalAlignment.MiddleAlign,  _ 
                               rcCell, True, e.Graphics, _PrintFont)
            Next
End Sub

Fitting it all onto a page

The printed page is divided into three areas: the header, the body and the footer. There is also an InterSectionSpacing property that specifies a gap to use between the sections. These are all expressed as percentages of the page height and setting any of them to zero will omit that section.

The body section is worked out from what remains of the page height when the header, footer and inter section spacing have been added up and this is used to calculate how many rows can possibly fit on each page:

    Private Function RowsPerPage(ByVal GridLineFont As Font, _
                                ByVal e As Graphics) As Integer

        Return (_PageContentRectangle.Height / _ 
                ((_CellGutter * 2) + _Rowheight)) - 2

    End Function

Settings that change the look of the grid

The color and width of the lines around the sections can be set with the HeaderPen, FooterPen and GridPen properties respectively.

The font to use for each of the sections can be set with the HeaderFont, FooterFont and PrintFont properties respectively.

Using the class to preview and print a DataGrid

If you have a data grid on a form that you want to preview and optionally print using this class you can add a System.Windows.Forms.PrintPreviewDialog to your form and a Print menu and add the following code to it:

    Private GridPrinter As DataGridPrinter

    Private Sub MenuItem_File_print_Click(ByVal sender As Object, _ 
                                   ByVal e As System.EventArgs) _ 
                                   Handles MenuItem_File_print.Click

        If GridPrinter Is Nothing Then
            GridPrinter = New DataGridPrinter(Me.DataGrid1)
        End If

        With GridPrinter
            .HeaderText = "Some text"
            .HeaderHeightPercent = 10
            .FooterHeightPercent = 5
            .InterSectionSpacingPercent = 2
            '\\ Set any other properties to 

            'affect the look of the grid...

        End With

        With Me.PrintPreviewDialog1
            .Document = GridPrinter.PrintDocument
            If .ShowDialog = DialogResult.OK Then
                GridPrinter.Print()
            End If
        End With
    End Sub