Here is an example of a form with three radio buttons: Small, Medium, and Large:

To create a radio button, on the Toolbox, you can click the RadioButton control . To programmatically create a radio button, declare a variable of type RadioButton, use the gcnew operator to allocation memory for it and add it to the Controls collection of its parent. Because radio buttons always come as a group, you should include them in another control that visibly shows that the radio buttons belong together. The most common control used for this purpose is the group box created using the GroupBox control.

Unlike most of other controls that can be positioned anywhere, a radio button should not be placed directly on a form. Instead, a radio button should be positioned in a container that belongs to a form. The typical container is the group box. When a radio button is added to a group box, the location of the radio button is relative to its parent. This location is easy to specify if you are visually designing the application. If you are programmatically creating it, make sure you specify the location based on the control that will hold the radio button. Here are examples:

#include <windows.h>

#using <System.dll>
#using <System.Drawing.dll>
#using <System.Windows.Forms.dll>

using namespace System;
using namespace System::Drawing;
using namespace System::Windows::Forms;

public ref class CExercise : public Form
{
private:
    RadioButton ^ radSmall;
    RadioButton ^ radMedium;
    RadioButton ^ radLarge;
    GroupBox    ^ grpPizzaSize;

public:
    CExercise()
    {
	InitializeComponent();
    }

private:
    void InitializeComponent()
    {
        grpPizzaSize = gcnew GroupBox;
        grpPizzaSize->Size = System::Drawing::Size(160, 120);
        grpPizzaSize->Location = Point(20, 10);

        radSmall = gcnew RadioButton;
        radSmall->Location = Point(20, 20);

        radMedium = gcnew RadioButton;
        radMedium->Location = Point(20, 50);

        radLarge = gcnew RadioButton;
        radLarge->Location = Point(20, 80);

        grpPizzaSize->Controls->Add(radSmall);
        grpPizzaSize->Controls->Add(radMedium);
        grpPizzaSize->Controls->Add(radLarge);

        Controls->Add(grpPizzaSize);
    }
};

[STAThread]
int APIENTRY WinMain(HINSTANCE hInstance,
		     HINSTANCE hPrevInstance,
		     LPSTR lpCmdLine,
		     int nCmdShow)
{
    Application::Run(gcnew CExercise);

    return 0;
}

This would produce:

To indicate what a radio button represents, it is accompanied by text, also referred to as its caption. To specify the caption of a radio button at a design time, type a string in the Text field of its Properties window. To programmatically specify the caption of a radio button, assign a string to its Text property. Here are examples:

void InitializeComponent()
{
        grpPizzaSize = gcnew GroupBox;
        grpPizzaSize->Text = "Pizza Size";
        grpPizzaSize->Size = System::Drawing::Size(160, 120);
        grpPizzaSize->Location = Point(20, 10);

        radSmall = gcnew RadioButton;
        radSmall->Text = "Small";
        radSmall->Location = Point(20, 20);

        radMedium = gcnew RadioButton;
        radMedium->Text = "Medium";
        radMedium->Location = Point(20, 50);

        radLarge = gcnew RadioButton;
        radLarge->Text = "Large";
        radLarge->Location = Point(20, 80);

        grpPizzaSize->Controls->Add(radSmall);
        grpPizzaSize->Controls->Add(radMedium);
        grpPizzaSize->Controls->Add(radLarge);

        Controls->Add(grpPizzaSize);
    }
}

This would produce:

The application we are going to create is used to calculate the amount owed on a loan using the following formula:

	P = Principal
	r = Annual (Interest) Rate
	m = Number of Compounding Periods per Year
	n = Total Number of Compounding Periods
	A = Amount Earned After n periods

1. Start Microsoft Visual Studio
2. To create a new application, on the main menu, click File -> New Project
3. In the middle list, click Windows Forms Application
4. Change the Name to CompoundInterest1
5. Design the form as followed:
    

   Control Name Text Additional Properties GroupBox   Loan Setup   Label   Principal:   TextBox txtPrincipal 0.00 TextAlign: Right Label   Interest Rate:   TextBox txtInterestRate 8.25 TextAlign: Right Label   %   Label   Number of Periods:   TextBox txtPeriods 1 TextAlign: Text Label   years   GroupBox   Compound Frequency   RadioButton rdoMonthly Monthly   RadioButton rdoQuarterly Quarterly   RadioButton rdoSemiannually Semiannually   RadioButton rdoAnnually Annually   GroupBox   Results   Label   Interest Earned:   TextBox txtInterestEarned 0.00 TextAlign: Right ReadOnly: True Label   Future Value:   TextBox txtFutureValue 0.00 TextAlign: Right ReadOnly: True Button btnCalculate Calculate   Button btnClose Close

6. On the form, double-click the Close button and implement its OnClick() event as follows:
   

   System::Void btnClose_Click(System::Object^  sender, System::EventArgs^  e)
   {
   	Close();
   }

7. To test the application, press F5
8. Close the form and return to your programming environment

If you add only one radio button to a container, when the application starts, the lone radio button would appear with an empty round circle. If the user clicks that lone radio button, the radio button's circle becomes filled with a dot and the user cannot remove or change this aspect. If you equip a container with more than one radio button, the user can click the desired one to select it and only one of the radio buttons can be selected at a given time. The radio button that is selected is referred to as checked. To support this description, the RadioButton class is equipped with a property named Checked.

At design time, to select a radio button, in the Properties window, set its Checked property to True. At run time, to programmatically select a radio button, assign a true value to its Checked property. To find out whether a particular radio button is selected, get the value of its Checked property. You can also programmatically check a radio button. Here is an example:

void InitializeComponent()
{
        grpPizzaSize = gcnew GroupBox;
        grpPizzaSize->Text = "Pizza Size";
        grpPizzaSize->Size = System::Drawing::Size(160, 120);
        grpPizzaSize->Location = Point(20, 10);

        radSmall = gcnew RadioButton;
        radSmall->Text = "Small";
        radSmall->Location = Point(20, 20);

        radMedium = gcnew RadioButton;
        radMedium->Text = "Medium";
        radMedium->Location = Point(20, 50);

        radLarge = gcnew RadioButton;
        radLarge->Text = "Large";
        radLarge->Location = Point(20, 80);

        grpPizzaSize->Controls->Add(radSmall);
        grpPizzaSize->Controls->Add(radMedium);
        grpPizzaSize->Controls->Add(radLarge);

        Controls->Add(grpPizzaSize);

	radMedium->Checked = true;
}

If the user clicks a radio button, since this control is primarily a button, the radio button that was clicked in the group fires a Click event. This is the most regularly used event of a radio button. Normally, when the user clicks a button in the group, the round box of that button becomes filled and the Click event is fired. If the user clicks a button that is already checked, nothing changes in the round box of that button but the Click event fires again. In some cases, you may want to execute code only if the checked state of a button has actually changed rather than being interested in whether the button was clicked or not. Fortunately, if you are interested only when the checked stated of a button is changed, you can use the CheckedChanged event. This event is fired whenever the checked state of a button is modified. Here is an example of implementing it:

System::Void rdoSmall_CheckedChanged(Object ^ sender, EventArgs ^ e)
{
        txtPizzaPrice->Text = "$8.75";
}

1. Return to the form.
   On the form, click Monthly
2. In the Properties window, double-click Checked to set its value to True
3. On the form, double-click the Calculate button and implement its Click() event as follows:
   

   System::Void btnCalculate_Click(Object ^ sender, EventArgs ^ e)
   {
       double principal = 0.00,
              interestRate = 0.00,
              interestEarned = 0.00;
       double futureValue = 0.00,
              ratePerPeriod = 0.00,
              periods = 0;
       int compoundType = 0;
   
       // Retrieve the value of the principal
       principal = double::Parse(txtPrincipal->Text);
   
       // Retrieve the interest rate
       interestRate = double::Parse(txtInterestRate->Text) / 100;
   
       // Find out what radio button was clicked
       // to apply the compound frequency
       if( rdoMonthly->Checked )
           compoundType = 12;
       else if( rdoQuarterly->Checked )
           compoundType = 4;
       else if( rdoSemiannually->Checked )
           compoundType = 2;
       else
           compoundType = 1;
   
       // Get the number of periods
       periods = double::Parse(txtPeriods->Text);
   
       // These values will make the calculation easier to read
       double i = interestRate / compoundType;
       double n = compoundType * periods;
   
       // Perform the necessary calculations
       ratePerPeriod = interestRate / periods;
       futureValue = principal * Math::Pow(1 + i, n);
       interestEarned = futureValue - principal;
   
       // Display the values in the appropriate text boxes
       txtInterestEarned->Text = interestEarned.ToString("C");
       txtFutureValue->Text = futureValue.ToString("C");
   }

4. Test the application
    
   
5. After using it, close the form and return to your programming environment

By default, the round box of a radio button is positioned to the left side of its accompanying label but you have many options. Besides the left position, you can position the round box to the top, the right, or the bottom etc side of its label. The position of the round box with regards to its label is controlled by the CheckAlign property which is a value of type ContentAlignment. To specify it at design time, access the Properties window of the radio button and select the desired value from the CheckAlign field. You can also change this property programmatically. Here are examples:

void InitializeComponent()
{
        grpPizzaSize = gcnew GroupBox;
        grpPizzaSize->Text = "Pizza Size";
        grpPizzaSize->Size = System::Drawing::Size(160, 120);
        grpPizzaSize->Location = Point(20, 10);

        radSmall = gcnew RadioButton;
        radSmall->Text = "Small";
        radSmall->CheckAlign = ContentAlignment::TopCenter;
        radSmall->Location = Point(20, 20);

        radMedium = gcnew RadioButton;
        radMedium->Text = "Medium";
        radMedium->CheckAlign = ContentAlignment::TopCenter;
        radMedium->Location = Point(20, 50);

        radLarge = gcnew RadioButton;
        radLarge->Text = "Large";
        radLarge->CheckAlign = ContentAlignment::TopCenter;
        radLarge->Location = Point(20, 80);

        grpPizzaSize->Controls->Add(radSmall);
        grpPizzaSize->Controls->Add(radMedium);
        grpPizzaSize->Controls->Add(radLarge);

        Controls->Add(grpPizzaSize);
}

Besides the alignment of the check box, you can also control the alignment of the text with regards to the bounding rectangle of the control. This characteristic is controlled by the TextAlign property of the RadioButton class. The TextAlign property also is of type ContentAlignment.

By default, a radio button appears as a rounded box that gets filled with a big dot when the user selects it. Optionally, you can make a radio button appear as a toggle button. Normally, if you make one radio button appear as a button, you should apply the same characteristics on the other radio buttons of the same group. The button would appear as a rectangular object. When the user clicks such a button, it appears down:

If the user clicks another button, this button becomes up:

To change the appearance of a radio button, assign the Button or Normal value to its Appearance property. The Appearance property is based on the Appearance enumeration. Here are examples:

void InitializeComponent()
{
        grpPizzaSize = gcnew GroupBox;
        grpPizzaSize->Text = "Pizza Size";
        grpPizzaSize->Size = System::Drawing::Size(150, 120);
        grpPizzaSize->Location = Point(20, 10);

        radSmall = gcnew RadioButton;
        radSmall->Appearance = Appearance::Button;
        radSmall->Location = Point(20, 20);

        radMedium = gcnew RadioButton;
        radMedium->Appearance = Appearance::Button;
        radMedium->Location = Point(20, 50);

        radLarge = gcnew RadioButton;
        radLarge->Appearance = Appearance::Button;
        radLarge->Location = Point(20, 80);

        grpPizzaSize->Controls->Add(radSmall);
        grpPizzaSize->Controls->Add(radMedium);
        grpPizzaSize->Controls->Add(radLarge);

        Controls->Add(grpPizzaSize);
}

This would produce:

As you can see, you can apply the Appearance property to a radio button that does not have a caption. You can also use a caption. If you do, make sure you align the caption to make is good to see. Here are examples:

void InitializeComponent()
{
        grpPizzaSize = gcnew GroupBox;
        grpPizzaSize->Text = "Pizza Size";
        grpPizzaSize->Size = System::Drawing::Size(150, 120);
        grpPizzaSize->Location = Point(20, 10);

        radSmall = gcnew RadioButton;
        radSmall->Text = "Small";
        radSmall->Appearance = Appearance::Button;
        radSmall->TextAlign = ContentAlignment::MiddleCenter;
        radSmall->CheckAlign = ContentAlignment::MiddleCenter;
        radSmall->Location = Point(20, 20);

        radMedium = gcnew RadioButton;
        radMedium->Text = "Medium";
        radMedium->Appearance = Appearance::Button;
        radMedium->TextAlign = ContentAlignment::MiddleCenter;
        radMedium->CheckAlign = ContentAlignment::MiddleCenter;
        radMedium->Location = Point(20, 50);

        radLarge = gcnew RadioButton;
        radLarge->Text = "Large";
        radLarge->Appearance = Appearance::Button;
        radLarge->TextAlign = ContentAlignment::MiddleCenter;
        radLarge->CheckAlign = ContentAlignment::MiddleCenter;
        radLarge->Location = Point(20, 80);

        grpPizzaSize->Controls->Add(radSmall);
        grpPizzaSize->Controls->Add(radMedium);
        grpPizzaSize->Controls->Add(radLarge);

        Controls->Add(grpPizzaSize);
}

This would produce:

If you configure your application and give the user the ability to change the appearance of the radio button from a round circle to a rectangular object and vice-versa, and if the user decides to change this appearance, when this is done, the control whose appearance was changed fires an AppearanceChanged event. The AppearanceChanged event is of type EventArgs, meaning that it does not carry any significant information other than to let you know that the appearance of the button was changed.