Best way to databind a group of radiobuttons in WinForms

Question

I'm currently working on databinding some of my existing Windows Forms, and I've ran into an issue figuring out the proper way of databinding a group of radiobutton controls within a group box.

My business object has an integer property which I want to databind against 4 radiobuttons (where each of them represents the values 0 - 3).

I'm currently binding against a presenter object which works as the binder between the form and the business object, and the way I've done it now is to have 4 separate properties which each binds against each of these values (I do use INotifyPropertyChanged, but not including that here):

Private int _propValue;

Public bool PropIsValue0 
{ 
  get { return _propValue == 0; }
  set
  {
    if (value) 
      _propValue = 0;
  }
}

Public bool PropIsValue1 { // As above, but with value == 1 }
Public bool PropIsValue2 { // As above, but with value == 2 }
Public bool PropIsValue3 { // As above, but with value == 3 }

And I then bind each of the radiobuttons to their respective property as above.

This does not seem right to me, so any advice are highly appreciated.

Answer 1

Following is a generic RadioGroupBox implementation in the spirit of ArielBH's suggestion (some code borrowed from Jay Andrew Allen's RadioPanel). Just add RadioButtons to it, set their tags to different integers and bind to the 'Selected' property.

public class RadioGroupBox : GroupBox
{
    public event EventHandler SelectedChanged = delegate { };

    int _selected;
    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;
    }

    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;
            SelectedChanged(this, new EventArgs());
        }
    }
}

Note that you can't bind to the 'Selected' property via the designer due to initialization order problems in InitializeComponent (the binding is performed before the radio buttons are initialized, so their tag is null in the first assignment). So just bind yourself like so:

    public Form1()
    {
        InitializeComponent();
        //Assuming selected1 and selected2 are defined as integer application settings
        radioGroup1.DataBindings.Add("Selected", Properties.Settings.Default, "selected1");
        radioGroup2.DataBindings.Add("Selected", Properties.Settings.Default, "selected2");
    }

Answer 2

I know this post is old but in my search for an answer for this same problem I came across this post and it didn't solve my problem. I ended up having a lightbulb go off randomly just a minute ago and wanted to share my solution.

I have three radio buttons in a group box. I'm using a List<> of a custom class object as the data source.

Class Object:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace BAL
{
class ProductItem
{

    // Global Variable to store the value of which radio button should be checked
    private int glbTaxStatus;
    // Public variable to set initial value passed from 
    // database query and get value to save to database
    public int TaxStatus
    {
        get { return glbTaxStatus; }
        set { glbTaxStatus = value; }
    }

    // Get/Set for 1st Radio button
    public bool Resale
    {
        // If the Global Variable = 1 return true, else return false
        get
        {
            if (glbTaxStatus.Equals(1))
            {
                return true;
            }
            else
            {
                return false;
            }
        }

        // If the value being passed in = 1 set the Global Variable = 1, else do nothing
        set
        {
            if (value.Equals(true))
            {
                glbTaxStatus = 1;
            }
        }
    }

    // Get/Set for 2nd Radio button
    public bool NeverTax
    {
        // If the Global Variable = 2 return true, else return false
        get
        {
            if (glbTaxStatus.Equals(2))
            {
                return true;
            }
            else
            {
                return false;
            }
        }

        // If the value being passed in = 2 set the Global Variable = 2, else do nothing
        set
        {
            if (value.Equals(true))
            {
                glbTaxStatus = 2;
            }
        }
    }

    // Get/Set for 3rd Radio button
    public bool AlwaysTax
    {
        // If the Global Variable = 3 return true, else return false
        get
        {
            if (glbTaxStatus.Equals(3))
            {
                return true;
            }
            else
            {
                return false;
            }
        }

        // If the value being passed in = 3 set the Global Variable = 3, else do nothing
        set
        {
            if (value.Equals(true))
            {
                glbTaxStatus = 3;
            }
        }
    }

// More code ...

Three seperate public variables with get/set accessing the same one global variable.

In the code behind, I have a function called during the Page_Load() setting all the controls databindings. For each radio button I add its own databinging.

radResale.DataBindings.Add("Checked", glbProductList, "Resale", true, DataSourceUpdateMode.OnPropertyChanged, false);
radNeverTax.DataBindings.Add("Checked", glbProductList, "NeverTax", true, DataSourceUpdateMode.OnPropertyChanged, false);
radAlwaysTax.DataBindings.Add("Checked", glbProductList, "Always", true, DataSourceUpdateMode.OnPropertyChanged, false);

I hope this helps someone!!

Answer 3

I think I would use my own GroupBox. I would bind the CustomGroupBox to your Model and set the correct RadioButton (using the tag or name properties) from the binded value.

Answer 4

This is my approach for binding a list of radio buttons to an enum.

Using the Enum as a string in the button's Tag property, I use the Binding.Format and Binding.Parse event to decide which button should be checked.

public enum OptionEnum
{
   Option1 = 0,
   Option2
}

OptionEnum _rbEnum = OptionEnum.Option1;
OptionEnum PropertyRBEnum
{
    get { return _rbEnum; }
    set
    {
        _rbEnum = value;
        RaisePropertyChanged("PropertyRBEnum");
    }
}

public static void FormatSelectedEnum<T>(object sender, ConvertEventArgs args) where T : struct
{
    Binding binding = (sender as Binding);
    if (binding == null) return;

    Control button = binding.Control;

    if (button == null || args.DesiredType != typeof(Boolean)) return;

    T value = (T)args.Value;
    T controlValue;

    if (Enum.TryParse(button.Tag.ToString(), out controlValue))
    {
        args.Value = value.Equals(controlValue);
    }
    else
    {
        Exception ex = new Exception("String not found in Enum");
        ex.Data.Add("Tag", button.Tag);

        throw ex;
    }
}

public static void ParseSelectedEnum<T>(object sender, ConvertEventArgs args) where T : struct
{
    Binding binding = (sender as Binding);
    if (binding == null) return;

    Control button = binding.Control;
    bool value = (bool)args.Value;

    if (button == null || value != true) return;

    T controlValue;

    if (Enum.TryParse(button.Tag.ToString(), out controlValue))
    {
        args.Value = controlValue;
    }
    else
    {
        Exception ex = new Exception("String not found in Enum");
        ex.Data.Add("Tag", button.Tag);

        throw ex;
    }
}

Then setup your data binding like this:

radioButton1.Tag = "Option1";
radioButton2.Tag = "Option2";

foreach (RadioButtonUx rb in new RadioButtonUx[] { radioButton1, radioButton2 })
{
    Binding b = new Binding("Checked", this, "PropertyRBEnum");
    b.Format += FormatSelectedRadioButton<OptionEnum>;
    b.Parse += ParseSelectedRadioButton<OptionEnum>;

    rb.DataBindings.Add(b);
}

Answer 5

I started to resolve the same problematic.

I used a RadioButtonBinding class which encapsulates all radiobuttons about an enum in the data source.

This following class keeps all radio buttons in a list and makes a lookup for the enum :

class RadioButtonBinding : ILookup<System.Enum, System.Windows.Forms.RadioButton>
{
    private Type enumType;
    private List<System.Windows.Forms.RadioButton> radioButtons;
    private System.Windows.Forms.BindingSource bindingSource;
    private string propertyName;

    public RadioButtonBinding(Type myEnum, System.Windows.Forms.BindingSource bs, string propertyName)
    {
        this.enumType = myEnum;
        this.radioButtons = new List<System.Windows.Forms.RadioButton>();
        foreach (string name in System.Enum.GetNames(this.enumType))
        {
            System.Windows.Forms.RadioButton rb = new System.Windows.Forms.RadioButton();
            rb.Text = name;
            this.radioButtons.Add(rb);
            rb.CheckedChanged += new EventHandler(rb_CheckedChanged);
        }
        this.bindingSource = bs;
        this.propertyName = propertyName;
        this.bindingSource.DataSourceChanged += new EventHandler(bindingSource_DataSourceChanged);
    }

    void bindingSource_DataSourceChanged(object sender, EventArgs e)
    {
        object obj = this.bindingSource.Current;
        System.Enum item = obj.GetType().GetProperty(propertyName).GetValue(obj, new object[] { }) as System.Enum;
        foreach (System.Enum value in System.Enum.GetValues(this.enumType))
        {
            if (this.Contains(value))
            {
                System.Windows.Forms.RadioButton rb = this[value].First();
                if (value.Equals(item))
                {
                    rb.Checked = true;
                }
                else
                {
                    rb.Checked = false;
                }
            }
        }
    }

    void rb_CheckedChanged(object sender, EventArgs e)
    {
        System.Windows.Forms.RadioButton rb = sender as System.Windows.Forms.RadioButton;
        System.Enum val = null;
        try
        {
            val = System.Enum.Parse(this.enumType, rb.Text) as System.Enum;
        }
        catch(Exception ex)
        {
            // cannot occurred if code is safe
            System.Windows.Forms.MessageBox.Show("No enum value for this radio button : " + ex.ToString());
        }
        object obj = this.bindingSource.Current;
        obj.GetType().GetProperty(propertyName).SetValue(obj, val, new object[] { });
        this.bindingSource.CurrencyManager.Refresh();
    }

    public int Count
    {
        get
        {
            return System.Enum.GetNames(this.enumType).Count();
        }
    }

    System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
    {
        return this.radioButtons.GetEnumerator();
    }

    public bool Contains(Enum key)
    {
        return System.Enum.GetNames(this.enumType).Contains(key.ToString());
    }

    public IEnumerable<System.Windows.Forms.RadioButton> this[Enum key]
    {
        get
        {
            return this.radioButtons.FindAll(a => { return a.Text == key.ToString(); });
        }
    }

    IEnumerator<IGrouping<Enum, System.Windows.Forms.RadioButton>> IEnumerable<IGrouping<Enum, System.Windows.Forms.RadioButton>>.GetEnumerator()
    {
        throw new NotImplementedException();
    }

    public void AddControlsIntoGroupBox(System.Windows.Forms.GroupBox gb)
    {
        System.Windows.Forms.FlowLayoutPanel panel = new System.Windows.Forms.FlowLayoutPanel();
        panel.Dock = System.Windows.Forms.DockStyle.Fill;
        panel.FlowDirection = System.Windows.Forms.FlowDirection.RightToLeft;
        foreach (System.Windows.Forms.RadioButton rb in this.radioButtons)
        {
            panel.Controls.Add(rb);
        }
        gb.Controls.Add(panel);
    }
}

You are using the class into a form by adding that code in the constructor of the form:

    public PageView()
    {
        InitializeComponent();
        RadioButtonBinding rbWidth = new RadioButtonBinding(typeof(Library.EnumConstraint), this.pageBindingSource, "ConstraintWidth");
        rbWidth.AddControlsIntoGroupBox(this.groupBox1);
        RadioButtonBinding rbHeight = new RadioButtonBinding(typeof(Library.EnumConstraint), this.pageBindingSource, "ConstraintHeight");
        rbHeight.AddControlsIntoGroupBox(this.groupBox3);
        this.pageBindingSource.CurrentItemChanged += new EventHandler(pageBindingSource_CurrentItemChanged);
    }

Answer 6

Set the tag name of your radio buttons to something that represents the value.

Create a string setting, for example, OptionDuplicateFiles, and give it the default value of the tag name for your default radio button.

To save your checked radio button:

Settings.Default.OptionDuplicateFiles = gbxDuplicateFiles.Controls
   .OfType<RadioButton>()
   .Where(b => b.Checked)
   .Select(b => b.Tag)
   .First()
   .ToString();

To load your checked radio button:

(gbxDuplicateFiles.Controls
   .OfType<RadioButton>()
   .Where(b => b.Tag.ToString() == Settings.Default.OptionDuplicateFiles)
   .First())
   .Checked = true;

Tada!

Answer 7

I liked the idea of a RadioButtonGroupBox but I decided to create a version that is self supporting. There is no reason to add value to Tag attribute or to introduce new value attributes. Any assigned radio button is still a member of the RadioButtonGroupBox and the sequence of radiobuttons is defined during development. Soo, I modified the code. Now I can get and set the selected radiobutton by index position, By Control Name and by Text. BTW Text is only useable if your asssigned Text is different for each radiobutton.

public class RadioButtonGroupBox : GroupBox
{
    public event EventHandler SelectedChanged = delegate { };

    int _nIndexPosCheckRadioButton = -1;
    int _selected;
    public int Selected
    {
        get
        {
            return _selected;
        }
    }


    public int CheckedRadioButtonIndexPos
    {
        set
        {
            int nPosInList = -1;
            foreach (RadioButton item in this.Controls.OfType<RadioButton>())
            {
                // There are RadioButtonItems in the list...
                nPosInList++;

                // Set the RB that should be checked
                if (nPosInList == value)
                {
                    item.Checked = true;
                    // We can stop with the loop
                    break;
                }
            }
            _nIndexPosCheckRadioButton = nPosInList;
        }
        get
        {
            int nPosInList = -1;
            int nPosCheckeItemInList = -1;

            foreach (RadioButton item in this.Controls.OfType<RadioButton>())
            {
                // There are RadioButtonItems in the list...
                nPosInList++;

                // Find the RB that is checked
                if (item.Checked)
                {
                    nPosCheckeItemInList = nPosInList;
                    // We can stop with the loop
                    break;
                }
            }
            _nIndexPosCheckRadioButton = nPosCheckeItemInList;
            return _nIndexPosCheckRadioButton;
        }
    }

    public string CheckedRadioButtonByText
    {
        set
        {
            int nPosInList = -1;
            foreach (RadioButton item in this.Controls.OfType<RadioButton>())
            {
                // There are RadioButtonItems in the list...
                nPosInList++;

                // Set the RB that should be checked
                if (item.Text == value)
                {
                    item.Checked = true;
                    // We can stop with the loop
                    break;
                }
            }
            _nIndexPosCheckRadioButton = nPosInList;
        }
        get
        {
            string cByTextValue = "__UNDEFINED__";
            int nPosInList = -1;
            int nPosCheckeItemInList = -1;

            foreach (RadioButton item in this.Controls.OfType<RadioButton>())
            {
                // There are RadioButtonItems in the list...
                nPosInList++;

                // Find the RB that is checked
                if (item.Checked)
                {
                    cByTextValue = item.Text;
                    nPosCheckeItemInList = nPosInList;
                    // We can stop with the loop
                    break;
                }
            }
            _nIndexPosCheckRadioButton = nPosCheckeItemInList;
            return cByTextValue;
        }
    }

    public string CheckedRadioButtonByName
    {
        set
        {
            int nPosInList = -1;
            foreach (RadioButton item in this.Controls.OfType<RadioButton>())
            {
                // There are RadioButtonItems in the list...
                nPosInList++;

                // Set the RB that should be checked
                if (item.Name == value)
                {
                    item.Checked = true;
                    // We can stop with the loop
                    break;
                }
            }
            _nIndexPosCheckRadioButton = nPosInList;
        }
        get
        {
            String cByNameValue = "__UNDEFINED__";
            int nPosInList = -1;
            int nPosCheckeItemInList = -1;

            foreach (RadioButton item in this.Controls.OfType<RadioButton>())
            {
                // There are RadioButtonItems in the list...
                nPosInList++;

                // Find the RB that is checked
                if (item.Checked)
                {
                    cByNameValue = item.Name;
                    nPosCheckeItemInList = nPosInList;
                    // We can stop with the loop
                    break;
                }
            }
            _nIndexPosCheckRadioButton = nPosCheckeItemInList;
            return cByNameValue;
        }
    }


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

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


    void radioButton_CheckedChanged(object sender, EventArgs e)
    {
        _selected = CheckedRadioButtonIndexPos;
        SelectedChanged(this, new EventArgs());
    }

}

Answer 8

My approach is to put each radio button into its own panel before binding them to a boolean property:

    public static Binding Bind<TObject>(this RadioButton control, object dataSource, string dataMember)
    {
        // Put the radio button into its own panel
        Panel panel = new Panel();
        control.Parent.Controls.Add(panel);
        panel.Location = control.Location;
        panel.Size = control.Size;
        panel.Controls.Add(control);
        control.Location = new Point(0, 0);

        // Do the actual data binding
        return control.DataBindings.Add("Checked", dataSource, dataMember);
    }

Answer 9

I would like to make an observation about the code block that might be helpful to people reading these posts. The following code may not always work as expected due to it's structure.

try
    {
      val = System.Enum.Parse(this.enumType, rb.Text) as System.Enum;
    }
    catch(Exception ex)
    {
      // cannot occurred if code is safe
      System.Windows.Forms.MessageBox.Show("No enum value for this radio button : " + ex.ToString());
    }
    object obj = this.bindingSource.Current;
    obj.GetType().GetProperty(propertyName).SetValue(obj, val, new object[] {
    }
  );
  this.bindingSource.CurrencyManager.Refresh();

If an error occurs in the try block, the catch block will be executed. The code will continue to execute after the catch block. Since there was no handling of binding source, the variables following the catch could end up in a indeterminate state and may throw another exception that may or may not be handled.

A better approach is as follows

 try
        {
            val = System.Enum.Parse(this.enumType, rb.Text) as System.Enum;

        object obj = this.bindingSource.Current;
        obj.GetType().GetProperty(propertyName).SetValue(obj, val, new object[] { });
        this.bindingSource.CurrencyManager.Refresh();
        }
        catch(EntityException ex)
        {
            // handle error
        }
        catch(Exception ex)
        {
            // cannot occurred if code is safe
            System.Windows.Forms.MessageBox.Show("No enum value for this radio button : " + ex.ToString());
        }

This allows the enum value error to be handled as well as other errors that may occur. However use the EntityException or variations of it before the Exception block (all decendents of Exception have to come first). One can get specific entity state information for a entity framework error by using the entity framework classes instead of the Exception base class. This can be helpful for debugging or providing clearer run time messages for the user.

When I setup try-catch blocks I like to view it as a "layer" on top of the code. I make decisions about the flow of the exceptions through out the program, their display to the user, and what ever cleanup is required to allow the program to continue working properly without objects in a indeterminate state that can cascade to other errors.