Custom group box not binding to bindingsource

Question

I need to bind a GroupBox to a BindingSource, which in turn is bound to the following object:

public class CustomerType
{
    public int Id {get; set;}
    public string Name {get; set;}
    public MemberType MemberType {get; set;}
}

public enum MemberType {Adult, Child}

I followed this answer to create a custom GroupBox. I also set the data bindings as follows:

groupBoxMemberType.DataBindings.Add("Selected", this.bindingSource, "MemberType");

However, when loading an existing object, I get the following exception:

DataBinding cannot find a row in the list that is suitable for all bindings.

The exception occurs when setting the data source:

customerType = customerTypeRequest.Load(id);
bindingSource.DataSource = customerType;  //raises exception

What am I missing? Is there an alternative to get radio buttons to bind to a datasource, specifically a BindingSource?

Answer 1

This is the changed code:

[DefaultBindingProperty("Selected")]
public class RadioGroupBox : GroupBox
{
    #region events

    [Description("Occurs when the selected value changes.")]
    public event SelectedChangedEventHandler SelectedChanged;

    public class SelectedChangedEventArgs : EventArgs
    {
        public int Selected { get; private set; }

        internal SelectedChangedEventArgs(int selected)
        {
            this.Selected = selected;
        }
    }
    public delegate void SelectedChangedEventHandler(object sender, SelectedChangedEventArgs e);

    #endregion

    private int selected;

    [Browsable(false)]
    [Bindable(BindableSupport.Yes, BindingDirection.TwoWay)]
    [Description("The selected value associated with this control."), Category("Data")]
    public int Selected
    {
        get { return selected; }
        set
        {
            int val = 0;
            var radioButton = this.Controls.OfType<RadioButton>()
                .FirstOrDefault(radio =>
                    radio.Tag != null
                   && int.TryParse(radio.Tag.ToString(), out val) && val == value);

            if (radioButton != null)
            {
                radioButton.Checked = true;
                selected = val;
            }
        }
    }

    protected override void OnControlAdded(ControlEventArgs e)
    {
        base.OnControlAdded(e);

        var radioButton = e.Control as RadioButton;
        if (radioButton != null)
            radioButton.CheckedChanged += radioButton_CheckedChanged;
    }

    protected void OnSelectedChanged(SelectedChangedEventArgs e)
    {
        if (SelectedChanged != null)
            SelectedChanged(this, e);
    }

    private void radioButton_CheckedChanged(object sender, EventArgs e)
    {
        var radio = (RadioButton)sender;
        int val = 0;
        if (radio.Checked && radio.Tag != null
             && int.TryParse(radio.Tag.ToString(), out val))
        {
            selected = val;
            OnSelectedChanged(new SelectedChangedEventArgs(selected));
        }
    }
}

Further to setting the Tag property to the corresponding int value of the enum, you need to subscribe to the SelectedChanged event in your form, eg:

private void radioGroupBoxMemberType_SelectedChanged(object sender, SelectedChangedEventArgs e)
{
    customerType.MemberType = (MemberType)e.Selected;
}

Improvements to this class would be:

1. Inherit from RadioButton and use a new property instead of the Tag property.

2. Access and set the bindingsource property directly in the control to avoid subscribing to the event.