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CreateCell event cellelement is always null

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GridView

This is a migrated thread and some comments may be shown as answers.

34 Answers, 1 is accepted

answered on 04 Nov 2010, 09:27 PM

Hi LLC,

Welcome to the forums...

You need to use the CellFormatting event. the below example shows changing the cell back color if the cell text property = "Name" (change to suite your condition)

Let me know if you need further help
Richard

Private Sub RadGridView1_CellFormatting(ByVal sender As System.Object, ByVal e As Telerik.WinControls.UI.CellFormattingEventArgs) Handles RadGridView.CellFormatting

Dim cell As GridDataCellElement = TryCast(e.CellElement, GridDataCellElement)

If cell IsNot Nothing Then

If cell.Text = "Name" Then

cell.BackColor = Color.Aqua

cell.GradientStyle = GradientStyles.Solid

cell.DrawFill = True

Else

cell.ResetValue(LightVisualElement.DrawBorderProperty, ValueResetFlags.Local)

cell.ResetValue(LightVisualElement.BorderBoxStyleProperty, ValueResetFlags.Local)

cell.ResetValue(LightVisualElement.BorderWidthProperty, ValueResetFlags.Local)

cell.ResetValue(LightVisualElement.BorderColorProperty, ValueResetFlags.Local)

End If

End Sub

answered on 05 Nov 2010, 12:22 PM

Thanks, Richard. It's a little more complicated. I would only want to do the process only once because it doesn't depend on the values in the cells, it depens on the values I have in another table of a database (Let's say it's the structure) and these values correspond to the values I have in the grid in position (I hope you have understood me). If for example I sort the grid the values don't correspond and it makes the process again. If I'm not mistaken Cellformating fires each time the grid is modified. I was trying to do this process in DataBindingComplete event but it seems cell.style.backcolor doesn't work (it doesn't change the colour). Another question: Could I access enabled property in this event?, I don't find it. I would need it in order to disable some checkboxes which don't fulfil the condition.

Thanks for your help and I apologize for my bad english.

answered on 05 Nov 2010, 12:32 PM

Hi LLC,

You would still need to use the CellFormatting event because of the new virtualization system that the RadGridView uses which gives it it's good performance. For more information on virtualization and it's implications see this link

I'd suggest getting your database values outside of this event and comparing them.

As per the example, you should be using

cell.BackColor

Not

cell.style.backcolor

The enabled property for the cell is part of the CellElement, and you can reach it from within the CellFormatting event.

hope that helps, but let me know if you have further questions.

Richard

answered on 05 Nov 2010, 02:04 PM

Hello,

It is always null because there you can set another type of the cell, based on some conditions, basically you can do something like this:

void radGridView1_CreateCell(object sender, GridViewCreateCellEventArgs e)

{

e.CellElement = new CustomCellElement(e.Column, e.Row);

}

Where you can say that this cell should be a custom cell element.

But as Richard said you can use either the CellFormatting event to color specific cells, or the RowFormatting to format rows:
A very basic example could be this:

void radGridView1_CellFormatting(object sender, CellFormattingEventArgs e)

{

if (e.CellElement.IsSelected)

{

e.CellElement.BackColor = Color.Red;

}

else

{

e.CellElement.ResetValue(LightVisualElement.BackColorProperty, Telerik.WinControls.ValueResetFlags.Local);

}

void radGridView1_RowFormatting(object sender, RowFormattingEventArgs e)

{

if (e.RowElement.IsSelected)

{

e.RowElement.BackColor = Color.Red;

}

else

{

e.RowElement.ResetValue(LightVisualElement.BackColorProperty, Telerik.WinControls.ValueResetFlags.Local);

}

Hope this helps, if you have any other questions or comments, please let me know,

Best Regards,
Emanuel Varga

answered on 05 Nov 2010, 05:56 PM

Thanks to both. I'm using CellFormatting event but I'm having problems with some cells. Namely they are checkboxes and I want some of them disabled. I'm doing some tests simply asking about the value of the checkbox (if it's unchecked I try to disable it setting cell.enabled=false, it works in most of the cells but in some it isn't working; sometimes it disable cells with value true and sometimes it doesn't disable cells with value false). Another question is about method resetvalue, the compiler doesn't recognize LightVisualElement: I see is a radproperty object and I declare it but it hasn't backcolorproperty or drawborder property. I'm investigating about its use: Is it necessary for what I want to get?

Thanks for your answers.

answered on 08 Nov 2010, 12:24 PM

Thanks to both (Richard and Emanuel) for assisting me.

This is the code: (I've made some progress but I'm still not getting the functionality I want).

Some considerations:
-Rad is an alias for Telerik.Wincontrols.UI

-primeraVez (spanish for first time) it's a boolean declared in the form. Its purpose is avoiding the code to execute every time cellformatting is handled. I only want this to be done the first time the grid is painted because I don't want the cells enabled to disable if I uncheck them. Maybe this should be done in another event? (I've tried in DataBindingComplete but I don't have access to enabled property and besides it can have some problems due to UI virtualization as Richard pointed).

Curious thing about this: If I remove the code concerning primeraVez it works well (it disables cells with checkbox value false and enables cells with checkbox value true) but as I have said before if I uncheck a cell enabled it will been disabled after editing.

-I've tried casting the cell to GridCheckBoxCellElement but I get the same result.

-I attach a picture of the form showing the grid indicating the wrong cells. (The initial values of the checkbox cells have been set in DataBindingComplete event depending on the values of a table in a database).

Thanks guys again for your help.

Private Sub DG1_CellFormatting(ByVal sender As Object, ByVal e As Telerik.WinControls.UI.CellFormattingEventArgs) Handles DG1.CellFormatting

If primeraVez

Then

             Dim celda As Rad.GridDataCellElement = TryCast(e.CellElement, Rad.GridDataCellElement) 
             Dim indiceFila As Integer = e.CellElement.RowIndex 
             Dim indiceColumna As Integer = e.CellElement.ColumnIndex

If celda IsNot Nothing Then

Select Case celda.ColumnInfo.HeaderText.ToUpper

Case "BIEN".ToUpper, "MAL".ToUpper

If celda.Value = False Then

celda.BackColor = Color.Red

celda.Enabled = False

Else

celda.ResetValue(Rad.LightVisualElement.BackColorProperty, Telerik.WinControls.ValueResetFlags.Local)

'celda.BackColor = Color.White

celda.Enabled = True

End If

End Select

'Last cell: I set boolean variable to false to indicate I don't want the code to be executed when grid is painted for the first time.

                    'I control it asking if I have reached the last cell of the grid (Maybe there is a better way).

                    'If I remove this verification cells enable and disable well so I think the problem is here.

If primeraVez And indiceFila = DG1.Rows.Count - 1 AndAlso indiceColumna = DG1.Columns.Count - 1 Then

primeraVez = False

End If

End Sub

answered on 08 Nov 2010, 01:35 PM

picture1.JPG

Hi, Richard. It's this way:

+Without "PrimeraVez" boolean all cells are OK but If I uncheck a cell (enabled) this cell gets disabled, I want to keep it enabled.
+With "PrimeraVez" boolean some cells are wrong (disabled when they should be enabled and enabled when they should be disabled) but when I uncheck cells enabled they keep enabled (it's what I want).

I hope you understand me

PS: Check out the attached picture.

answered on 08 Nov 2010, 03:01 PM

Hi LLC,

To change the back colour of a cell you need to use the Cellformatting event. Please try the very first exmaple that I gave: I.e.

Private Sub RadGridView1_CellFormatting(ByVal sender As System.Object, ByVal e As Telerik.WinControls.UI.CellFormattingEventArgs) Handles RadGridView.CellFormatting

Dim cell As GridDataCellElement = TryCast(e.CellElement, GridDataCellElement)

If cell IsNot Nothing Then

If cell.Text = "Name" Then

cell.BackColor = Color.Aqua

cell.GradientStyle = GradientStyles.Solid

cell.DrawFill = True

Else

cell.ResetValue(LightVisualElement.DrawBorderProperty, ValueResetFlags.Local)

cell.ResetValue(LightVisualElement.BorderBoxStyleProperty, ValueResetFlags.Local)

cell.ResetValue(LightVisualElement.BorderWidthProperty, ValueResetFlags.Local)

cell.ResetValue(LightVisualElement.BorderColorProperty, ValueResetFlags.Local)

End If

End Sub

the reason that there is more than one back color is that you can apply a gradient to blend in color from one to another.

Please try the above example so we can continue to hel solve your issues

Thanks
Richard

answered on 08 Nov 2010, 05:46 PM

Hi, Richard. Using your example setting the backcolor is working (By the way in DataBindingComplete it doesn't never work, however forecolor it works). But I still have the same problem, if I uncheck the cell the color changes and I don't want that (I'd like it always stayed the same color if initially was checkes though after I uncheck it). I've set readonly to false in the cells I don't want to be modified in DataBindingComplete event. This way cells initially unchecked can't be modified and they have the backcolor I want but as I have told you if I uncheck a cell initially checked (its readonly property is false) the backcolor changes and I don't want that. Is there any way to access readonly property in CellFormatting event? If I could verify its value I think I could solve this definitely.

Maybe I should try the aproach you told some posts ago: "Adding another column with a value that does not change (a boolean) and tie the enabled property of the checkbox to that." (I would need two extra columns in that case I think one for each boolean column I want to control).

Anyways, thanks again for your effort and assistance.

Accepted

answered on 16 Nov 2010, 10:52 AM

Hello LLC,

Because in the DataBindingComplete you are setting the Tag value for the CellInfo and in the CellFormatting you are reading it for the CellElement, please take a look at the following code:

void radGridView1_CellFormatting(object sender, CellFormattingEventArgs e)

{

if (e.CellElement.RowInfo.Cells[0].Tag != null && e.CellElement.RowInfo.Cells[0].Tag.Equals(true))

{

e.CellElement.BackColor = Color.Red;

e.CellElement.DrawFill = true;

}

else

{

e.CellElement.ResetValue(LightVisualElement.BackColorProperty, ValueResetFlags.Local);

e.CellElement.ResetValue(LightVisualElement.DrawFillProperty, ValueResetFlags.Local);

}

void radGridView1_DataBindingComplete(object sender, GridViewBindingCompleteEventArgs e)

{

foreach (var row in radGridView1.Rows)

{

if (row.Index % 2 == 0)

{

row.Cells[0].Tag = true;

}

Hope this helps, if you have any other questions or comments, please let me know,

Best Regards,
Emanuel Varga
Telerik WinForms MVP

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CreateCell event cellelement is always null

34 Answers, 1 is accepted