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HtmlInputRadioButton Class   Input Radio Element

Creates a selectable radio button control.

Declarative Syntax

<input type=radio id="accessID" runat="server"
   checked
   name = "radiobuttongroup"
   value = "radioButtonValue"
>

For information on the individual members of this class, see HtmlInputRadioButton in the class library.

• This control does not require a closing tag.

The HtmlInputRadioButton control creates a single radio button input field. By default, each individual radio button can be selected.

You can group a set of radio buttons together in cases where only one button from the set of options needs to be selected. This is done by setting a common value for the name attribute on each radio button in the group.

For example, the following snippet creates a group of radio buttons in which only one radio button may be selected.

<input type=radio name="optgroup1">Red
<input type=radio name="optgroup1">White
<input type=radio name="optgroup1">Blue

The selected state must be still be tested on the individual radio buttons, however.

The HtmlInputRadioButton enables programming of the HTML <input type=radio> element. The sample below illustrates use of the HtmlInputRadioButton control.

This example shows a simple way to find the selected radiobutton from a group of HtmlRadioButton controls. In this case, the checked property is simply evaluated and a message of the result is rendered via a <p runat=server> generic control.

Responding to User Selection in Radio Button Controls Run Sample | View Source

Note that the HtmlRadioButton control does not have an event that notifies the server when a user has selected a radio button option.

You must rely on using one of the button controls — such as the HtmlInputButton, HtmlInputImage, or HtmlButton — to cause a postback that will allow to program the HtmlRadioButton control itself.

To respond to User Selection in Radio button controls:

1. Declare a set of radio button controls, a button control that will cause postback when clicked by the user, and a <span> control to render the postback message.

   <form runat="server">
   
      <p><b>The first president of the United States was:</b></p>
   
      <table width=300 cellpadding=5 bgcolor="beige" style="border:1px inset">
      <tr><td><label><input type=radio id="Radio1" name="choices"
         runat="server">Abraham Lincoln</label></td></tr>
      <tr><td><label><input type=radio id="Radio2" name="choices"
         runat="server">Christopher Columbus</label></td></tr>
      <tr><td><label><input type=radio id="Radio3" name="choices"
         runat="server">George Washington</label></td></tr>
      <tr><td><label><input type=radio id="Radio4" name="choices"
         runat="server">Robert Plant</label></td></tr>
      </table>
   
      <p><button onServerClick="chkAnswer" runat="server">Submit</button>
   
      <p id="msg" runat="server" />
   
   </form>

2. Create event handling code to process the information gathered from the radio button group.

   <script language="C#" runat="server">
   string [ ] answers = {
      "Abraham Lincoln came a tad bit later.",
      "Christopher Columbus was an explorer, <br>not a United States President.",
      "Correct. George Washington was the first President <br>of the United States of America.",
      "Robert Plant was the lead vocalist of Led Zeppelin, <br>not a United States President."};
   
   void chkAnswer ( object src, EventArgs e ) {
      string txt = "";
      if ( Radio1.Checked )
         txt += answers [ 0 ];
      else if ( Radio2.Checked )
         txt += answers [ 1 ];
      else if ( Radio3.Checked )
         txt += answers [ 2 ];
      else if ( Radio4.Checked )
         txt += answers [ 3 ];
      msg.InnerHtml = txt;
   }
   </script>

HtmlInputRadioButton Class   Input Radio Element   Web Forms Events and Handlers