Getting problem to select the checked radio button

Question

Can any one help me to get the values of selected radio button which are place inside the listview control in asp.net using c# 

 

i try this code 

 

RadioButton rb1 = (RadioButton)ListView1.FindControl("RadioButton1");

if (rb1.Checked == true)

{

Label1.Text = rbl1;

}

 

but is shows me the following error

 

Object reference not set to an instance of an object.