WPF Binding custom list indexer

Question

I'm trying to make a screen with lots of controls using mvvm It's a settings screen that I want to allow the user to search for the settings he wants, leaving the others invisible.

I wouldn't want to have to create a property for every control, instead I'd like to create a list and index every item from it to a control.

However, for ease of maintenance, I would like to use a custom indexer, in this case a string

I created this list

public class ObservConfigList: ObservableCollection<ConfigModel>
{
    public ConfigModel this[string find]
    {
        get => this.FirstOrDefault(x => x.Config == find);
        set
        {
            var indice = this.IndexOf(this.FirstOrDefault(x => x.Config == find));
            if (indice >= this.Count)
                this[indice] = value;
        }
    }
}

And the xaml was like this

<Grid DataContext="{Binding ListConfig[EMPRESA]}" Style="{StaticResource visibConvert}">
        <Grid.ColumnDefinitions>                
            <ColumnDefinition Style="{StaticResource col1}"/>
            <ColumnDefinition Style="{StaticResource col2}"/>
        </Grid.ColumnDefinitions>
        <TextBlock Text="{Binding Descricao}"/>
        <ComboBox Grid.Column="1" Text="{Binding Valor}">
            <ComboBoxItem Content="SIM"/>
            <ComboBoxItem Content="NÃO"/>
        </ComboBox>
    </Grid>

my viewmodel

  private ObservConfigList _listConfig = new ObservConfigList();
    public ObservConfigList ListConfig { get => _listConfig; set => _listConfig = value; }
    private void ConfigViewModel()
    {
        ConfigEmpresa = new ConfigModel();         

        ConfigEmpresa.Descricao = "Empresa";
        ConfigEmpresa.IsVisible = true;
        ConfigEmpresa.Config = "EMPRESA";
        ListConfig.Add(ConfigEmpresa);
    }

It even worked as I expected at runtime, but I don't know if this is the correct way to do it and in xaml a notification keeps showing that the EMPRESA index is invalid.

if it works as expected at runtime and designer doesn't crash, then you are doing fine. xaml editor is not perfect. it might have detected integer index implemented in ObservableCollection class and complains about string — ASh, Nov 04 '21 at 16:28
you're probably right, but it's really annoying to see this error showing up in the error list of vs. even compiling and working, the error list will fill with these notifications since I would do this for each control. — Maicon, Nov 04 '21 at 16:48

score 0 · Accepted Answer · answered Nov 04 '21 at 17:18

I found this question

and modified the code from my list to do so

 public class ObservConfigList
{
    private ObservableCollection<ConfigModel> _listConfig = new ObservableCollection<ConfigModel>();
    public ObservableCollection<ConfigModel> ListConfig { get => _listConfig; set => _listConfig = value; }

    public ConfigModel this[string find]
    {
        get => ListConfig.FirstOrDefault(x => x.Config == find);
        set
        {
            var indice = ListConfig.IndexOf(ListConfig.FirstOrDefault(x => x.Config == find));
            if (indice >= ListConfig.Count)
                ListConfig[indice] = value;
        }
    }
}

This way it no longer displays error notifications.

WPF Binding custom list indexer

1 Answers1