Wpf datagrid validationrule for unique field

validation, wpf, wpfdatagrid

Solution

I finally got things working!

Here's the solution:

In the XAML I added the following ValidationStep:

<my:UniqueNameSolidWoodRule CurrentCollection="{StaticResource CurrentSolidWoodCollection}" ValidationStep="CommittedValue"/>

This way I'm getting a BindingExpression object instead of a string as the first parameter of the overridden Validate method, which gives me much more information about the record to validate like the HashCode I can use to check if I'm comparing the same object.

Here's the updated Validate method:

public class UniqueNameSolidWoodRule : ValidationRule
{
    public CollectionViewSource CurrentCollection { get; set; }

    public override ValidationResult Validate(object value, CultureInfo cultureInfo)
    {
        if (value != null)
        {
            ObservableCollection<SolidWood_VM> castedCollection = (ObservableCollection<SolidWood_VM>)CurrentCollection.Source;

            SolidWood_VM curValue = (SolidWood_VM)((BindingExpression)value).DataItem;

            foreach (SolidWood_VM swVM in castedCollection)
            {
                if (curValue.GetHashCode() != swVM.GetHashCode() && swVM.Designation == curValue.Designation.ToString())
                {
                    return new ValidationResult(false, ResourcesManager.Instance.GetString("DuplicatedRecord"));
                }
            }
        }

        return new ValidationResult(true, null);
    }
}

Problem

I've got a suclassed ValidationRule named UniqueNameSolidWoodRule to validate for duplicate entries in a datagrid. Here's the code: ``` public class UniqueNameSolidWoodRule : ValidationRule { public CollectionViewSource CurrentCollection { get; set; } public override ValidationResult Validate(object value, CultureInfo cultureInfo) { if (value != null) { ObservableCollection<SolidWood_VM> castedCollection = (ObservableCollection<SolidWood_VM>)CurrentCollection.Source; foreach (SolidWood_VM swVM in castedCollection) { if (swVM.Designation == value.ToString()) { return new ValidationResult(false, ResourcesManager.Instance.GetString("DuplicatedRecord")); } } } return new ValidationResult(true, null); } } ``` And here's the XAML snippet: ``` <DataGrid.Resources> <CollectionViewSource x:Key="CurrentSolidWoodCollection" Source="{Binding Path=SolidWoods}" /> </DataGrid.Resources> <DataGridTextColumn x:Name="Column2" Header="{x:Static p:Resources.Designation}" Width="auto"> <DataGridTextColumn.Binding> <Binding Path="Designation" ValidatesOnDataErrors="True" UpdateSourceTrigger="LostFocus"> <Binding.ValidationRules> <my:UniqueNameSolidWoodRule CurrentCollection="{StaticResource CurrentSolidWoodCollection}"/> </Binding.ValidationRules> </Binding> </DataGridTextColumn.Binding> </DataGridTextColumn> ``` My problem is that sometimes this rule compares the value with its own row. How could I prevent this? It seems to me that I need a row.index property associated with the value to compare, but unfortunnally I can't figure a way out to achieve this.

Original source