WPF

<Style x:Key="dataGridCurrencyCellStyle" 
        BasedOn="{StaticResource dataGridCellStyle}"
        TargetType="{x:Type DataGridCell}">

    <Setter Property="Width" Value="75"/>
    <Setter Property="TextBlock.TextAlignment" Value="Right"/>
    <Setter Property="TextBlock.Text" Value="{Binding StringFormat={}{0:0.##}}"/>
    <Setter Property="IsEnabled" Value="{Binding DataContext.AreFieldsEnabled, ElementName=budgetControl}"/>

</Style>

private void LoadTable()
{
    if (Budgets.Count > 0)
    {
        // 1- Create the data table

        BudgetTable = null;
        BudgetTable = new DataTable();

        // Add the first column
        DataColumn column = new DataColumn();
        column.ColumnName = "Type";
        column.DataType = System.Type.GetType("System.String");
        column.ReadOnly = false;
        BudgetTable.Columns.Add(column);

        // Get a distinct list of Plan/Elevations
        List<string> planElevations = new List<string>();

        switch (BudgetType)
        {
            case BudgetType.Job:
                var sheets = JobSequenceSheets.Where(x => x.Status == "New").ToList();
                planElevations = sheets.Select(x => $"{x.Plan}{x.Elevation}").ToList();
                break;

            case BudgetType.Project:
                planElevations = ProjectPlanTypeSummaries.Select(x => $"{x.Plan}{x.Elevation}").ToList();
                break;

            default:
                throw new ArgumentException("Unhandled CASE statement");
                break;
        }

        // Add a column for every distinct Plan/Elevation
        foreach (var planElevation in planElevations)
        {
            column = new DataColumn();

            column.ColumnName = planElevation;
            column.Caption = planElevation;
            column.DataType = System.Type.GetType("System.Decimal");
            column.ReadOnly = false;

            BudgetTable.Columns.Add(column);
        }

        // 2 - Now Bind Columns

        // Set up the columns list
        DataGridColumns = new ObservableCollection<DataGridColumn>();

        // Get a list of column names from the Budget Table
        string[] columnNames = (from dc in BudgetTable.Columns.Cast<DataColumn>()
                                select dc.ColumnName).ToArray();

        // Go through each column
        foreach (string item in columnNames)
        {
            // Create binding
            Binding binding = new Binding(item);
            string styleName = "";

            // Get binding mode and style name
            if (item == "Type")
            {
                binding.Mode = BindingMode.OneTime;
                styleName = "budgetGridCellStyle";
            }
            else
            {
                binding.Mode = BindingMode.TwoWay;
                binding.UpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged;
                styleName = "dataGridCurrencyCellStyle";
            }

            // Get the style
            var style = Application.Current.FindResource(styleName) as Style;

            // Bind the column
            var col = new DataGridTextColumn()
            {
                Header = item,
                Binding = binding,
                Visibility = Visibility.Visible,
                CellStyle = style
            };

            DataGridColumns.Add(col);
        }

        // 3 - Now add rows for the data
        foreach (var budget in Budgets)
        {
            AddRow(budget);
        }
    }
}

<DataGrid Grid.Row="1" 
            x:Name="budgetGrid" 
            Style="{StaticResource dataGridStyle}"
            GridLinesVisibility="All"
            ItemsSource="{Binding BudgetTable, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}">

    <i:Interaction.Behaviors>
        <cls:ColumnsBindingBehaviour Columns="{Binding DataContext.DataGridColumns, 
                                                        Mode=TwoWay, 
                                                        UpdateSourceTrigger=PropertyChanged, 
                                                        RelativeSource={RelativeSource AncestorType=DataGrid}}" />
    </i:Interaction.Behaviors>

    <behaviours:Interaction.Triggers>
        <behaviours:EventTrigger EventName="CellEditEnding">
            <behaviours:InvokeCommandAction Command="{Binding ElementName=budgetControl, Path=DataContext.CellEditedCommand}" 
                                            PassEventArgsToCommand="True"/>
        </behaviours:EventTrigger>
    </behaviours:Interaction.Triggers>

</DataGrid>

protected virtual void OnChildDesiredSizeChanged(UIElement child);

protected override void OnChildDesiredSizeChanged(UIElement child)
{
    base.OnChildDesiredSizeChanged(child);
    child.Measure(new Size(double.PositiveInfinity, double.PositiveInfinity));
    child.Arrange(new Rect(BoundedVisual.GetLocation(child), child.DesiredSize));
}

public event EventHandler LayoutUpdated;

<Canvas>
    <RichTextBox Canvas.Top="50" Canvas.Left="80">
</Canvas>

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