WPF DataGrid Validation.HasError is always false (MVVM)

Question

I have some trouble getting the Information if there are ValidationErrors inside the Datagrid / the DataGridCells. What I'm trying to do is to Disable a Button via Commands (CanExecute) basedOn the presence or absence of Validation Errors. Therefore I bind the the DataGrid's Validation.HasError to the CommandParameter on the Button. The Validation is implemented with IDataErrorInfo in the ViewModel and works just fine. Any DataGridCell containing a wrong value gets a red Border and a Tooltip describing the Error. What I just cant get to work is Binding that Button's CommandParameter to Validation.HasError on the DataGrid. If i debug this issue, Validation.HasError is always false. Why? And how can i fix it? I tried virtually every "solution" I found here and elsewhere on the net. Nothing worked so far. My DataGrid XAML: ``` <DataGrid x:Uid="DataGrid_1" Name="SomeDataGrid" Grid.Column="0" Grid.Row="1" Grid.RowSpan="2" ItemsSource="{Binding SomeItems}" SelectedItem="{Binding SomeSelecte…

Accepted Answer

Ok i finally worked it out! The following Method from here does indeed work, but only after the Window containing my Datagrid is fully loaded (eg. in the Window / Usercontrol Loaded EventHandler):

```
public bool IsValid(DependencyObject parent)
{
    if (Validation.GetHasError(parent))
        return false;

// Validate all the bindings on the children
    for (int i = 0; i != VisualTreeHelper.GetChildrenCount(parent); ++i)
    {
        DependencyObject child = VisualTreeHelper.GetChild(parent, i);
        if (!IsValid(child)) { return false; }
    }

return true;
}
```

WPF DataGrid Validation.HasError is always false (MVVM)

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