Which Radio button in the group is checked?

Question

Using WinForms; Is there a better way to find the checked RadioButton for a group? It seems to me that the code below should not be necessary. When you check a different RadioButton then it knows which one to uncheck… so it should know which is checked. How do I pull that information without doing a lot of if statements (or a switch).

     RadioButton rb = null;

     if (m_RadioButton1.Checked == true)
     {
        rb = m_RadioButton1;
     }
     else if (m_RadioButton2.Checked == true)
     {
        rb = m_RadioButton2;
     }
     else if (m_RadioButton3.Checked == true)
     {
        rb = m_RadioButton3;
     }

Engstrom

The underlying code does not know which one to uncheck, it just iterates all the RadioButton controls below the same parent of the changed control and unchecks the one previously checked. – Licht

Are you using WinForms or ASP.Net? – Persephone

Answer 1

You could use LINQ:

var checkedButton = container.Controls.OfType<RadioButton>()
                                      .FirstOrDefault(r => r.Checked);

Note that this requires that all of the radio buttons be directly in the same container (eg, Panel or Form), and that there is only one group in the container. If that is not the case, you could make List<RadioButton>s in your constructor for each group, then write list.FirstOrDefault(r => r.Checked).

Persephone

Should that be s.FirstOrDefault instead of list.FirstOrDefault in the second paragraph of your answer? – Carbo

@Phoenix: s is a pluralization, not a variable name. – Persephone

Excellent answer, but did not really answer OP's main question. See my answer. – Cimbri

for you vb.net guys, I'll save you a trip to the Telerik converter: Dim checkedButton = radConnections.Controls.OfType(Of RadioButton)().FirstOrDefault(Function(r) r.Checked) – Cornhusking

Answer 2

You can wire the CheckedEvents of all the buttons against one handler. There you can easily get the correct Checkbox.

// Wire all events into this.
private void AllCheckBoxes_CheckedChanged(Object sender, EventArgs e) {
    // Check of the raiser of the event is a checked Checkbox.
    // Of course we also need to to cast it first.
    if (((RadioButton)sender).Checked) {
        // This is the correct control.
        RadioButton rb = (RadioButton)sender;
    }
}

Exceptional

Should be this instead - if (((RadioButton)sender).Checked) – Brutish

There's no CheckedChanged in WPF's RadioButton where did you get it from? – Filibeg

Answer 3

For those without LINQ:

RadioButton GetCheckedRadio(Control container)
{
    foreach (var control in container.Controls)
    {
        RadioButton radio = control as RadioButton;

        if (radio != null && radio.Checked)
        {
            return radio;
        }
    }

    return null;
}

Dyne

Answer 4

The OP wanted to get the checked RadioButton BY GROUP. While @SLaks' answer is excellent, it doesn't really answer the OP's main question. To improve on @SLaks' answer, just take the LINQ one step further.

Here's an example from my own working code. Per normal WPF, my RadioButtons are contained in a Grid (named "myGrid") with a bunch of other types of controls. I have two different RadioButton groups in the Grid.

To get the checked RadioButton from a particular group:

List<RadioButton> radioButtons = myGrid.Children.OfType<RadioButton>().ToList();
RadioButton rbTarget = radioButtons
      .Where(r => r.GroupName == "GroupName" && r.IsChecked)
      .Single();

If your code has the possibility of no RadioButtons being checked, then use SingleOrDefault() (If I'm not using tri-state buttons, then I always set one button "IsChecked" as a default selection.)

Roubaix

r.GroupName == "GroupName" and r.IsChecked are of different types (bool and bool?), you should have used r.IsChecked.Value, which is of type bool. – Saltwater

try .Where(r => r.GroupName == "GroupName" && r.IsChecked == true) because r.IsChecked is nullable bool property. – Preterhuman

what does myGrid refer to here. – Laurettalaurette

@Saltwater Could you tell what is "radioButtons" here? – Desmund

@Preterhuman Could you tell what is "radioButtons" here? – Desmund

@BellaSwan - I've edited the original answer, it should be clear for you now. – Saltwater

@Saltwater the edits will take time to be approved yet. Could you not explain in the comments? – Desmund

@BellaSwan - have a look at the code - you create a list of all the radio buttons and assign it to a variable. And then, on the same variable you need to run the Where selection and assign it to rbTarget. – Saltwater

Answer 5

You can use the CheckedChanged event for all your RadioButtons. Sender will be the unchecked and checked RadioButtons.

However

Answer 6

Sometimes in situations like this I miss my youth, when Access was my poison of choice, and I could give each radio button in a group its own value.

My hack in C# is to use the tag to set the value, and when I make a selection from the group, I read the value of the tag of the selected radiobutton. In this example, directionGroup is the group in which I have four five radio buttons with "None" and "NE", "SE", "NW" and "SW" as the tags on the other four radiobuttons.

I proactively used a button to capture the value of the checked button, because because assigning one event handler to all of the buttons' CHeckCHanged event causes EACH button to fire, because changing one changes them all. So the value of sender is always the first RadioButton in the group. Instead, I use this method when I need to find out which one is selected, with the values I want to retrieve in the Tag property of each RadioButton.

  private void ShowSelectedRadioButton()
    {
        List<RadioButton> buttons = new List<RadioButton>();
        string selectedTag = "No selection";
        foreach (Control c in directionGroup.Controls)
        {
            if (c.GetType() == typeof(RadioButton))
            {
                buttons.Add((RadioButton)c);
            }
        }
        var selectedRb = (from rb in buttons where rb.Checked == true select rb).FirstOrDefault();
        if (selectedRb!=null)
        {
             selectedTag = selectedRb.Tag.ToString();
        }

        FormattableString result = $"Selected Radio button tag ={selectedTag}";
        MessageBox.Show(result.ToString());
    }

FYI, I have tested and used this in my work.

Joey

Mithridatism

Modifying only the 'FormatableString' result, I was able to use the code in my program. I was also not aware of radioButton Tag. This is how the answers should be. Great Sir. – Laurettalaurette

Answer 7

You can use an Extension method to iterate the RadioButton's Parent.Controls collection. This allows you to query other RadioButtons in the same scope. Using two extension methods, you can use the first determine whether any RadioButtons in the group are selected, then use the second to get the selection. The RadioButton Tag field can be used to hold an Enum to identify each RadioButton in the group:

    public static int GetRadioSelection(this RadioButton rb, int Default = -1) {
        foreach(Control c in  rb.Parent.Controls) {
            RadioButton r = c as RadioButton;
            if(r != null && r.Checked) return Int32.Parse((string)r.Tag);
        }
        return Default;
    }

    public static bool IsRadioSelected(this RadioButton rb) {
        foreach(Control c in  rb.Parent.Controls) {
            RadioButton r = c as RadioButton;
            if(r != null && r.Checked) return true;
        }
        return false;
    }

Here's a typical use pattern:

if(!MyRadioButton.IsRadioSelected()) {
   MessageBox.Show("No radio selected.");
   return;
}
int selection = MyRadioButton.GetRadioSelection;

Sizemore

Answer 8

In addition to the CheckedChangedEvent wiring one could use the Controls "Tag" property to distinguish between the radio buttons... an (spaghetti code) alternative would be the "TabIndex" property ;P

Bay

it means you could use quickly switch-case's on the selected radiobutton id (using the property System.Windows.Forms.Control.Tag) please dont rate down if you simply dont understand my addition to the question. – Bay

Answer 9

A simple way to handle this is to capture the CheckedChanged event for each of the radio buttons and have each one set their value in the Tag field of their container. Then when you're ready to read which radio button is clicked, just use the Tag field of the container.

    private void rbUnread_CheckedChanged(object sender, EventArgs e)
    {
        if (rbUnread.Checked)
            pnlStatus.Tag = 1;
    }
    private void rbRead_CheckedChanged(object sender, EventArgs e)
    {
        if (rbRead.Checked)
            pnlStatus.Tag = 2;
    }
    private void rbUnfinished_CheckedChanged(object sender, EventArgs e)
    {
        if (rbUnfinished.Checked)
            pnlStatus.Tag = 3;
    }

Solidago

Answer 10

if you want to save the selection to file or any else and call it later, here what I do

string[] lines = new string[1];

lines[0]  = groupBoxTes.Controls.OfType<RadioButton>()
            .FirstOrDefault(r => r.Checked).Text;

File.WriteAllLines("Config.ini", lines);

then call it with

string[] ini = File.ReadAllLines("Config.ini");
groupBoxTes.Controls.OfType<RadioButton>()
.FirstOrDefault(r => (r.Text == ini[0])).Checked = true;

Newfoundland

Answer 11

If you want to get the index of the selected radio button inside a control you can use this method:

public static int getCheckedRadioButton(Control c)
{
    int i;
    try
    {
        Control.ControlCollection cc = c.Controls;
        for (i = 0; i < cc.Count; i++)
        {
            RadioButton rb = cc[i] as RadioButton;
            if (rb.Checked)
            {
                return i;
            }
        }
    }
    catch
    {
        i = -1;
    }
    return i;
}

Example use:

int index = getCheckedRadioButton(panel1);

The code isn't that well tested, but it seems the index order is from left to right and from top to bottom, as when reading a text. If no radio button is found, the method returns -1.

Update: It turned out my first attempt didn't work if there's no radio button inside the control. I added a try and catch block to fix that, and the method now seems to work.

Conspicuous

Answer 12

The GroupBox has a Validated event for this purpose, if you are using WinForms.

private void grpBox_Validated(object sender, EventArgs e)
    {
        GroupBox g = sender as GroupBox;
        var a = from RadioButton r in g.Controls
                 where r.Checked == true select r.Name;
        strChecked = a.First();
     }

Inlet

Answer 13

For developers using VB.NET

Private Function GetCheckedRadio(container) As RadioButton
    For Each control In container.Children
        Dim radio As RadioButton = TryCast(control, RadioButton)

        If radio IsNot Nothing AndAlso radio.IsChecked Then
            Return radio
        End If
    Next

    Return Nothing
End Function

Kg

Answer 14

Yet another try - Using event lambda expressions

As form initializes a single event handler can be assigned to all controls of type RadioButton in a group box, and use .tabIndex or .tag property to identify what option is checked when it changes.

This way you can subscribe to any of the events of each radio button in one go

int priceOption = 0;
foreach (RadioButton rbtn in grp_PriceOpt.Controls.OfType<RadioButton>())
{
    rbtn.CheckedChanged += (o, e) =>
    {
        var button = (RadioButton)o;
        if (button.Checked)
        {
            priceOption = button.TabIndex;
        }
    };
}

As events are assigned to radio buttons only, no type checking of sender is implemented.

Also notice as we loop all buttons this could be a perfect moment to assign data properties, change text etc.

Pretorius