asp.net core radio button helper renders always the same id for each radio button

Question

Create.cshtml // Rest form code removed for brevity

<div class="form-group">
<label for="GradingKey.HalfScoresCount">
    <input asp-for="GradingKey.HalfScoresCount" value="true" type="radio" />Yes
</label>
<span asp-validation-for="GradingKey.HalfScoresCount" class="text-danger" />
</div>

<div class="form-group">
<label for="GradingKey.HalfScoresCount">
    <input asp-for="GradingKey.HalfScoresCount" value="false" type="radio" />No
</label>
<span asp-validation-for="GradingKey.HalfScoresCount" class="text-danger" />
</div>

Created Html

<div class="form-group">
<label for="GradingKey.HalfScoresCount">
    <input value="true" type="radio" data-val="true" data-val-required="Das Feld &quot;HalfScoresCount&quot; ist erforderlich." id="GradingKey_HalfScoresCount" name="GradingKey.HalfScoresCount" />Yes
</label>
<span class="text-danger field-validation-valid" data-valmsg-for="GradingKey.HalfScoresCount" data-valmsg-replace="true" />
</div>

<div class="form-group">
<label for="GradingKey.HalfScoresCount">
    <input value="false" type="radio" id="GradingKey_HalfScoresCount" name="GradingKey.HalfScoresCount" />No
</label>
<span class="text-danger field-validation-valid" data-valmsg-for="GradingKey.HalfScoresCount" data-valmsg-replace="true" />
</div>

Why has the generated html the same id for both radio buttons?

How can I avoid that?

Answer 1

Why has the generated html the same id for both radio buttons?

By default, the id field for an input will be the name of the property set in the asp-for tag helper value. You've got the same value listed twice:

<input asp-for="GradingKey.HalfScoresCount" value="true" type="radio" />Yes
<input asp-for="GradingKey.HalfScoresCount" value="false" type="radio" />No

How can I avoid that?

Simply specify your own id attribute values:

<input asp-for="GradingKey.HalfScoresCount" value="true" type="radio" id="myFirstId" />Yes
<input asp-for="GradingKey.HalfScoresCount" value="false" type="radio" id="mySecondId" />No

As long as you do not modify the name attribute, the model binding will still function properly.