Why is IValueConverter not called for DataGrid autogenerated Column

Question

In an autogenerated datagrid column, I want to replace a certain value (-1) with blank.

I created an IValueConverter:

<ValueConversion(GetType(DataRowView), GetType(String))>
Public Class UsageConversion
    Implements IValueConverter

    Public Function Convert(value As Object, targetType As System.Type, parameter As Object, culture As System.Globalization.CultureInfo) As Object Implements System.Windows.Data.IValueConverter.Convert
        Dim model As ProgModel = DirectCast(value, ProgModel)
        If model.Usage = -1 Then
            Return ""
        Else
            Return model.Usage.ToString
        End If
    End Function

    Public Function ConvertBack(value As Object, targetType As System.Type, parameter As Object, culture As System.Globalization.CultureInfo) As Object Implements System.Windows.Data.IValueConverter.ConvertBack
        Return Nothing
    End Function
End Class

And bound it into the OnAutoGeneratingColumn method:

        Dim dgtc As DataGridTextColumn = TryCast(e.Column, DataGridTextColumn)
        If dgtc IsNot Nothing Then 
                Dim UsageBinding = New Binding()
                UsageBinding.Converter = New UsageConversion
                Dim tbStyle As New Style
                tbStyle.TargetType = GetType(TextBlock)
                tbStyle.Setters.Add(New Setter(TextBlock.TextProperty, UsageBinding))
                dgtc.ElementStyle = tbStyle
        End If

The OnAutoGeneratingColumn runs well, but the Convert code does not run - setting a breakpoint in it shows it is never called.

Any ideas why?

I am using .Net 4.0

Thanks!

Does a breakpoint in your `OnAutoGeneratingColumn` handler get hit? — Sheridan, Jan 20 '14 at 09:06
Yes, a breakpoint shows that the code I posted from OnAutoGeneratingColumn does run, and that dgtc.ElementStyle setters includes a setter with Property = Text — GilShalit, Jan 20 '14 at 11:30
Have you tried setting `UsageBinding.UpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged;`? Maybe it *is* working, but just not *when* expected? — Sheridan, Jan 20 '14 at 11:34
@Sheridan, tried this now, no change. I mean the Converter to be called when the data is loaded into the column. — GilShalit, Jan 20 '14 at 11:42

Sheridan · Answer 1 · 2014-01-20T18:52:14.823

2

I'm not sure why you're trying to set this Binding on the ElementStyle... surely, you just want to set that Binding on the whole column:

    Dim dgtc As DataGridTextColumn = TryCast(e.Column, DataGridTextColumn)
    If dgtc IsNot Nothing Then 
            Dim UsageBinding = New Binding()
            UsageBinding.Converter = New UsageConversion
            dgtc.Binding = UsageBinding

edited Jan 20 '14 at 18:52

answered Jan 20 '14 at 11:54

Sheridan

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Oh... just beaten to it. If this is the solution, please award the accepted answer to @potehin143. – Sheridan Jan 20 '14 at 11:55
As @potehin143 only posted a comment, I can just +1 it. Tanks anyway - you were right on the mark. – GilShalit Jan 20 '14 at 18:03
and BTW, no need for "YourPropertyName". Dim UsageBinding = New Binding() works just fine. – GilShalit Jan 20 '14 at 18:04
Ok, thanks for getting back to me... I'll update my example accordingly. – Sheridan Jan 20 '14 at 18:52

potehin143 · Accepted Answer · 2014-01-20T11:49:00.483

0

I Guess you have to set UsageBinding.Path property

Binding.Path property it not set so you column it binded to nothing and that is why no value comes to Converter

try this

Dim UsageBinding = New Binding(e.PropertyName)
UsageBinding.Converter = New UsageConversion
dgtc.Binding=UsageBinding

edited Jan 20 '14 at 11:49

answered Jan 20 '14 at 10:30

potehin143

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4
9

Thanks. This did not make any difference. – GilShalit Jan 20 '14 at 11:27
1

I guess you dont need style there Just bind your column to data via Converter – potehin143 Jan 20 '14 at 11:50
My comment about this not making a difference was for the suggestion before the edit. As it stands now - this is the correct answer - thanks! – GilShalit Jan 20 '14 at 18:06

Why is IValueConverter not called for DataGrid autogenerated Column

2 Answers2