public class CurrencyConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
var val = value as Employee;
if (val == null)
return "C";
var cultureInfo = new CultureInfo("fr-FR");
if (val.EmployeeID > 1005)
return "F";                
return cultureInfo.NumberFormat.CurrencySymbol;
}

public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}

public class GridCellCurrencyRendererExt : GridCellCurrencyRenderer
{
public override void OnInitializeDisplayElement(DataColumnBase dataColumn, TextBlock uiElement, object dataContext)
{
base.OnInitializeDisplayElement(dataColumn, uiElement, dataContext);
}
public override void OnInitializeEditElement(DataColumnBase dataColumn, CurrencyTextBox uiElement, object dataContext)
{
base.OnInitializeEditElement(dataColumn, uiElement, dataContext);
var binding = new Binding {Converter=new CurrencyConverter() };
uiElement.SetBinding(CurrencyTextBox.CurrencySymbolProperty, binding);
}
}

public class SfDataGridBehavior : Behavior<SfDataGrid>
{
protected override void OnAttached()
{
base.OnAttached();
this.AssociatedObject.CellRenderers.Remove("Currency");
this.AssociatedObject.CellRenderers.Add("Currency", new GridCellCurrencyRendererExt());
}  
}