How to call TryUpdateModel outside a data operation method

Question

• VS2012, .NET 4.51

I have a user control that contains a ListView that is using model binding. So far so good. I want to display a list of objects based on how the user has manipulated the view mode. To this end I have a public property called Roles. However when I call TryUpdateModel() from inside there, I receive the exception:

TryUpdateModel' must be passed a value provider or alternatively must be invoked from inside a data-operation method of a control that uses model binding for data binding

Now while I understand I can drop out of edit mode by doing:

lvData.EditIndex = -1;

and then in the UpdateMethod call TryUpdateModel(), I was wondering how I could call TryUpdateModel without having to wire up the method to do the update. To put it another way how/where/what do I supply for the IValueProvider parameter to TryUpdateModel().

/// <summary>
///     Initialise the user control
/// </summary>
/// <param name="aRoles">List of roles to display</param>
public void Activate(List<RoleInfo> aRoles)
{
    //List we will be binding
    _ViewModel = new List<MembershipRolesViewModel>();

    //Transfer the supplied list into the view model
    foreach (RoleInfo roleInfo in aRoles)
    {
        _ViewModel.Add(new MembershipRolesViewModel
        {
            RoleDisplayName = roleInfo.RoleDisplayName,
            RoleHint = roleInfo.RoleHint,
            RoleName = roleInfo.RoleName,
            RoleSelected = roleInfo.RoleSelected
        });
    }
}

//ListView.SelectMethod points here
public IQueryable<MembershipRolesViewModel> RolesSelect()
{
    return _ViewModel.AsQueryable();
}

//Property to return the roles as manipulated by the user
public List<RoleInfo> Roles
{
    get
    {
        List<RoleInfo> result = new List<RoleInfo>();
        TryUpdateModel(_ViewModel);

        foreach (MembershipRolesViewModel membershipRolesViewModel in _ViewModel)
        {
            result.Add(new RoleInfo
            {
                RoleDisplayName = membershipRolesViewModel.RoleDisplayName,
                RoleHint = membershipRolesViewModel.RoleHint,
                RoleName = membershipRolesViewModel.RoleName,
                RoleSelected = membershipRolesViewModel.RoleSelected
            });
        }

        return result;
    }
}

TryUpdateModel must be passed a value provider or alternatively must be invoked from inside a data-operation method of a control that uses model binding for data binding.

Answer 1

There's no simple way to get values from ListView items. You have to loop on items and extract their values.

var bindableTemplate = lv.ItemTemplate as IBindableTemplate;
foreach (ListViewItem item in lv.Items)
{
    var dic = bindableTemplate.ExtractValues(item).Cast<System.Collections.DictionaryEntry>().ToDictionary(k => (string)k.Key, v => v.Value);
    var provider = new DictionaryValueProvider<object>(dic, System.Globalization.CultureInfo.InvariantCulture);

    // Now we can update the item.
    TryUpdateModel<RoleInfo>(model, provider);
}

Or force the ListView to update own item.

public List<RoleInfo> Roles
{
    get
    {
        List<RoleInfo> result = new List<RoleInfo>();
        for (int i = 0; i < lv.Items.Count; i++)
            if (lv.Items[i].ItemType == ListViewItemType.DataItem)
                lv.UpdateItem(i, true);

        //...

        return result;
    }
}



public void lv_UpdateItem(int id)
{
    RoleInfo model = //...
    TryUpdateModel(model);
}

Hope this helps.