where should i place the code for events of drop down list and radio button event which are created at runtime table

Your Question is not very clear. What I understood is - You have created dynamic DropDownList and RadioButton and now you want to assign some Event to it.

Try as below code to assign an Event to your dynamically created DropDownList.

myDropdownList.SelectedIndexChanged += new EventHandler(myDropdownList_SelectedIndexChanged);
myDropdownList.AutoPostBack = true;

private void myDropdownList_SelectedIndexChanged(object sender, EventArgs e)
{
  //Write your Dropdown Selected Index Changed code here.

}

And try as below code to assign an Event to your dynamically created RadioButton.

myRadioButton.CheckedChanged += new EventHandler(this.myRadioButton_CheckedChanged);
myDropdownList.AutoPostBack = true;

private void myRadioButton_CheckedChanged(object sender, System.EventArgs e)
{
  //Write your RadioButton Changed code here.

}

Hope this helps.