RadioButtonList and their 'Value' property - asp.net

Question

I was wondering about the 'Value' property of an item in a RadioButtonList.
If I want to get the value of the selected Radio Button that is in the list, these must be unique or it will auto-select the first item it finds with the value I'm looking for. So no duplicate values.
Why is this? I've looked around the net, used them, and such so I know HOW it is working, but I would like to know WHY it works this way.
If I select an item in the list, it knows which item I selected. The button fills in, you can get the index of the item that is selected...so why doesn't it go: "Okay, you selected the item at index X. You also want the value? Okay, let me access the list, go to item X and get its value."
I can only think that when you want the value of an item, it is looking by value rather than by index then by value?
UPDATE 1:
In my particular case I was doing this:
I have 1 RadioButtonList that has 3 items(RadioButtons) in it. The following Select...Case occurs inside of a button click.
Select Case RadioButtonList1.SelectedItem.Text
Case "TextA"
Case "TextB"
//This RadioButton has a value of 200
Case "TextC"
//This RadioButton has a value of 200
End Select
This works for the first Case and only ONE other. As I debugged, the first and second cases went through fine. When I selected the third RadioButton, then execute the event, it will automatically select the second RadioButton because it has the same value as the third, but comes first in the list.
Changing one of the identical values fixes this.

Answer 1

Not sure I completely understand, Do you have your HTML, script to share? You might have a problem if you're using duplicate IDs to group the radio button set; you should just use same name attribute. In that case, if you try to get the value using selectElementById it will just grab the first one.
Since you "want to get the value of the selected Radio Button that is in the list", you can get that array of same-named inputs (getElementsByName) and loop through and look for the 'CHECKED' condition:
<input type="radio" name="cars" value="beamer" checked="checked">BMW<br><br>
<input type="radio" name="cars" value="prius">Prius<br><br>
<input type="radio" name="cars" value="volvo">Volvo<br><br>
<input type="radio" name="cars" value="beamer">BMW<br><br>
<input type="radio" name="cars" value="prius">Prius<br><br>
<input type="radio" name="cars" value="volvo">Volvo<br><br>
<p>Selected Car Value and Index:</p>
<div id="selectedCar"></div><br><br>
<button onclick="getVal()">Get Value and Index</button>
<script>
var getVal = function(){
var cars = document.getElementsByName('cars');
var result = document.getElementById("selectedCar");
for (var i = 0, length = cars.length; i < length; i++) {
if (cars[i].checked) {
result.innerHTML = "value: " + cars[i].value + " and index: " + i;
break;
}
}
}
</script>