Persist a value in an inherited class or create a custom parameter

Question

Hi

I am making some changes to a fairly old project.

It has a DataGrid with an Inherited Class 

Public Class CustomDataGridTextBox

          Inherits DataGridTextBoxColumn

and a Override Sub

Protected Overloads Overrides Sub Paint (.......

What it was doing was alternating the Data Grid Line colours

New Requirement is to break up some items in the DataGrid By categories

So I have added new lines to the data and sorted so they show up ad category headers (Production Stations)

And they would like the Category Header to be a different colour and then the alternating line colours to restart.

This did not sound too difficult but that has proven a trap

Setting the category header is no problem but restarting the alternating colours is

Previously the row was determined to be odd or even to set the colour.

Now I am intending to use an Integer to define what colour is used but it persists only for that text box.

How can I get it to extend its life so each call can refer to it and update it and set the desired colour?

All I need to do is have an integer variable that will hold its value for the next call?

Thanks for any Assistance

Doug

Answer 1

All I need to do is have an integer variable that will hold its value for the next call?

If this is really what you are trying to do, then declaring the variable as Static will solve the problem.
http://msdn.microsoft.com/en-us/library/z2cty7t8(v=vs.100).aspx

Answer 2

Hi Acamar,

I just worked out that this was not my problem,

The TextBoxColumn code Sub, as it says works on the columns. and holds the variable as it runs through each row. I have to find another way.

Thanks for your reply

Answer 3

In that case you may wish to provide a little more explanation.

You were previously setting the color of the control according to whether the line number in the grid was odd or even.   I think the reason that this rule no longer works is that you want the first item within any category to be the same color - that's probably what you mean by 'restarting'.  If I was doing this I would simnply retain the old rule and accept that some categories will start with one color and other categories will start with a different color.  Whatever, it seems that you have decided to store the original line numbers (before the headers get added) as properties of the text box, and use those (as odd or even) to determine the coloring. 

I think you are expecting a property of the custom text box class instance to be different for each cell that uses the class, and you will then color the cell according to that value.  To calculate that value, you would need to work through the rows in the grid assigning alternating numbers, and starting again after you hit a header cell.  Why use a value like that, when you could simply set the cell style properties, such as color?  Style properties, unlike the textbox instance, are unique to each cell.

Answer 4

Thanks Acamar,

I will look at that.

Sorry I did not post some code, it is on another disconnected PC.

Essentially you are correct:

Header row Colour A

First Data Row Colour B

Second Data Row Colour C

Subsequent Data Rows alternating B C B C etc

then another Header Row and starting over B C B C etc

I also understand what you are saying about retaining the old rule (I just felt it would look more professional to start each group the same way) and that would be a simpler solution.

Thanks for your help, I will consider options.

Doug

Answer 5

HI,

For this you can go with global class and use global variables into this class.

Answer 6

Hi,

I have got it partially working.

The requirement is that the Grid will have 3 Row background Colours (in this case the set BackColor, the set AlternatingBackColor and a constant 'Salmon'

That is working fine but my problem now is that clicking on a cell (which selects the row) or selecting the row from the Row Headers Column does not highlight the row correctly.

It used to set a Dark Blue BackColor.

Now it just inverts the text and it is not readable.

I could not find why this changed but whenever there is a paint over-ride it does so I am assuming the paint over-ride is setting the cells (and consequently the row) to the colours the over ride paint event sets.

OK so I figured I could force them to another colour in the same sub.

I moved the Class Module into the Project and tried to reference the DataGrid but could not get that to work so I sent an integer in the form to the current row number

And then tried to read that and compare with the paint 'rowNum' and then set the cell to another colour.

This seemed to work as if I set the variable in the for to say Row 2 it does colour Row 2

However if I set it using events in the form to the Row Number that is clicked etc it does not work

The variable changes value in the form (checked but using a break point)

But the variable in the Class Module does not reference this changed value (checked with Debug)

     

Any ideas?

Thanks

   'Over-ride Paint Method
        Protected Overloads Overrides Sub Paint(ByVal g As Graphics, _
                    ByVal bounds As Rectangle, ByVal source As CurrencyManager, _
                    ByVal rowNum As Integer, ByVal backBrush As Brush, _
                    ByVal foreBrush As Brush, ByVal alignToRight As Boolean)

            Static iRowColr As Integer = 0
            Dim oVal As Object = Me.GetColumnValueAtRow([source], rowNum)
            Dim stVal As String = ""
            If Not oVal Is DBNull.Value Then
                stVal = oVal.ToString
            End If

            'Dim dr As DataRow = CType(source.List().Item(rowNum), DataRowView).Row
            'stVal = dr(1).ToString.Trim


                If bColourHeader Then
                    If Me.HeaderText = "Wrk:" Then 'WorkStation Column
                        If stVal <> stHdRow Then 'Is it 1st Row of WorkStation ie Header Row
                            stHdRow = stVal 'Then Set Header Reference
                            iRowColr = 0 'Set Row Colour Index to Header Colour
                        Else
                            'Not 1st Row of Header
                            If iRowColr = 0 Then 'If Index is Header Colour then set to Alternate Colour
                                iRowColr = 2
                            ElseIf iRowColr = 1 Then 'If Index is Main Colour then set to Alt Colour
                                iRowColr = 2
                            ElseIf iRowColr = 2 Then 'If Index is Alt Colour then set to Main Colour
                                iRowColr = 1
                            End If
                        End If
                    ElseIf Me.HeaderText = "" Then 'Space Columns
                        iRowColr = 2 '    set to Alt Colour
                    Else '    Other Columns
                        If stVal = "" Then
                            iRowColr = 0
                        Else
                            If iRowColr = 0 Then
                                iRowColr = 2
                            ElseIf iRowColr = 1 Then
                                iRowColr = 2
                            ElseIf iRowColr = 2 Then
                                iRowColr = 1
                            End If
                        End If
                    End If
                Else
                    If iRowColr = 1 Then
                        iRowColr = 2
                    Else
                        iRowColr = 1
                    End If
                End If
            End If


            Dim colBackCol As Color = Me.DataGridTableStyle.BackColor
            Dim colAltBackCol As Color = Me.DataGridTableStyle.AlternatingBackColor
            Dim colBreakCol As Color = Color.LightSalmon
            Dim bshBackColour As SolidBrush = New SolidBrush(colBackCol)
            Dim bshAltColour As SolidBrush = New SolidBrush(colAltBackCol)
            Dim bshBreakColour As SolidBrush = New SolidBrush(colBreakCol)
            Dim colSelCol As Color = Color.DarkGreen
            Dim bshSelColour As SolidBrush = New SolidBrush(colSelCol)
            Dim iSeldRow As Integer = FormShopOrders.iCurrRow
            If (iSeldRow > 0) And iSeldRow = rowNum Then
                backBrush = bshSelColour
           Else
                If iRowColr = -1 Then
                    backBrush = bshSelColour
                ElseIf iRowColr = 0 Then
                    backBrush = bshBreakColour
                ElseIf iRowColr = 2 Then
                    backBrush = bshAltColour
                ElseIf iRowColr = 1 Then
                    backBrush = bshBackColour
                End If
            End If

            MyBase.Paint(g, bounds, source, rowNum, backBrush, foreBrush, alignToRight)

        End Sub

Answer 7

I presume the variable you are referring to is iSeldRow.

The class instance where this code is executing does not have any knowledge of or access to variables in the form unless you set the references up for it.   How you do that depends in part on how the class instance is created.  If it's created by code in the form (for instance at form load) or if it is a shared class then you can reference that class instance from the form - you have a reference variable for the class instance if you created the instance, or you use the class name as a reference if it is a shared class.   So you could create a class property, and update that property when the selected row changes using the class instance reference and the property name. 

Then, the code in the overloaded Paint event can reference the internal class variable for that property to get the row number it needs.

If my analysis of your code is correct you must have a declaration for the variable iSeldRow somewhere in that class - without it the code would not compile.   You need to remove that declaration, and change the code so it refers to the new property value instead.

Answer 8

Hi Acamar,

Thanks for your response,

It does not seem to be correct to me that the Class Module does not have access to the variable because as you say later the code would not compile if it could not access the public variable in the Form. Maybe I have not understood what you are saying?

Also as I said, if I initialise the variable in the form to a value say -1 or say 2 then the Class Module reacts appropriately to the value that I set.

What doesn't happen is that as the variable, in Form Class, changes its value reflecting the selected row it does not change the value in the Class Module.

Have I misunderstood something here?

I would still like to understand this but I have managed to get a solution to the problem I was having. I realised that the row was being selected and then painted over by the new paint code. So instead of trying to determine if the row was the selected row, I looked at the backbrush property and if its colour = the colour set for the SelectedRow I then bypast the code that recoloured the row.

Please continue to explain what is happening with the variable if I have missed something.

Thanks

Doug

Answer 9

If you have a structure such as

Class Form1
    Dim iSeldRow As Integer = 1
End Class

Class myModule
   If iSeldRow = ...
End Class

then the code will not compile.  If you give iSeldRow public visibility then you can do

Class myModule
   If Form1.iSeldRow = ...
End Class

because you are providing a full reference to the variable (assuming the default instance name) .  If you can reference the variable using the code you posted then that code must have been inserted into the Form1 class, whereas you description implied it was still in its own module.   That's why I queried my analysis of your code - despite your reference to the 'Class Module' the fact that the code compiled indicated that you had actually merged the module code into the Form1 class, making your access to the variable legal (and telling you that the problem was elsewhere).

Answer 10

Hi Acmar

The code is not in the form it is in its ow Class Module within the Project:

Solution '24x7Production' (...)

        .....

        .....

        - Production Recording

              .....

              - FormShopOrders.vb

              .....

           - ClassSODataGrid

_______________________________

  Public Class FormShopOrders

             Public iCurrRow As Integer = 2      'Set to 2 to test that Integer is passed

        .........

        .........

            Private Sub grdSelSO_SetRow (ByVal iRow As Integer)

                 ' iCurrRow = iRow    'Remarked out whil testing variable value is past to Class

            End Sub

           .......

   End Class

 

_____________________________________

   Public Class CustDGrid

        ......

   End Class

   Public Class CustTextBoxCol

        ......

       Protected Overloads Overrides Sub Paint(  ...,  ...., ....)

            ......

          Dim iSelRow As Integer = FormShopOrders.iCurrRow

           ......

      End Sub

   End Class

Yes it compiles with no errors

Setting iCurrRow to constant value of 2 then running the program, iSelRow gets set to 2

But then if I un remark the code in FormShopOrders iCurrRow gets set to the row number on the grid when you click the grid

but iSelRow is not updated it always holds its initial value.

Thanks

Answer 11

iSelRow is declared within the class in which it is being used so it will not cause a compile error.  The value you are setting it to corresponds to my second example where you explicitly reference the form instance that contains the variable:

          Dim iSelRow As Integer = FormShopOrders.iCurrRow

However, FormShopOrders is a class name.  It is usable as an instance name if you are asuming the default instance.  That is usually an unsafe assumption, but may be OK in this case.

Your testing is not telling you what you need to know.  Use code like this instead:
  Public Class FormShopOrders
            Public iCurrRow As Integer
             ...
            Private Sub grdSelSO_SetRow (ByVal iRow As Integer)
                 ICurrRow = 2 'Set to 2 for testing, or
                 ' iCurrRow = iRow    'Set to row number for running
            End Sub

   End Class

Then insert a breakpoint at the line that actually sets the value and make sure it gets set.