Getting value from html radio button - in aspx-c#

问题:

I have the following HTML source

<form name="Register1" action="Register.aspx" id="registerform" method="post" 
      runat="server" style="margin-top: 15px;">
    <input type="radio" name="Gender" value="male" />male
    <input type="radio" name="Gender" value="female" />female
</form>

My question is how can I get the selected value to variable in the c# page?

I tried this :

Gender = Request.Form["Gender"].ToString();

But it didn't work...

回答1:

place your code like this:

 if (Request.Form["Gender"] != null)
 {
     string selectedGender = Request.Form["Gender"].ToString();
 }

Note that Request.Form["Gender"] will be null if none of the RadioButtons are selected.

see the markup below

<form id="form1" runat="server" method="post">
    <input type="radio" name="Gender" value="male" id="test" checked="checked" />
    male
    <input type="radio" name="Gender" value="female" />female
    <input type="submit" value="test" />
    <asp:Button ID="btn" runat="server" Text="value" />
</form>

for both the buttons i.e input type="submit" and usual asp:button, Request.Form["Gender"] is going to have some value upon PostBack, provided, either of the RadioButtons is selected.

And yes, upon PostBack only, i.e. when you hit either of the buttons and not on first load.

回答2:

To start with you will need the form posted the Form collection won't have anything on the page load, so suppose you have a button and you click to submit the form then in the click event handler you can get the selected value with the code you have tried.

I guess the collection is null hence the NullReference exception when you access it.

It is better to access it like

if(!string.IsNullOrEmpty(Request.Form["Gender"]))
{

}

回答3:

Use a RadioButtonList

<asp:RadioButtonList id="RadioButtonList1" runat="server">
    <asp:ListItem value="male">male</asp:ListItem>
    <asp:ListItem value="female">female</asp:ListItem>
</asp:RadioButtonList>

and get the value with

RadioButtonList1.SelectedValue;

回答4:

if you are working with asp.net make sure that HTML control name by Request.Form contains these ct100$ with the name or id through which you are assessing. check the below example.

int rbratebyname = 0;

if (Request.Form["ctl00$ContentPlaceHolder1$rate"] != null)
{
    rbratebyname = int.Parse(Request.Form["ctl00$ContentPlaceHolder1$rate"]);
}