Blazor InputText with Required attribute but Disabled - .net-core

Question

So I have a model, other properties removed for brevity:
public class OutOfLimitReasonViewModel
{
[Required]
public int ReasonId { get; set; }
[Required(ErrorMessage = "Other Reason is required")]
public string OtherReason { get; set; }
}
Of course I have an EditForm on the .razor page and the InputText I care about looks like this:
<InputText #bind-Value="model.OtherReason" class="form-control" disabled="#(!OtherReasonRequired)" />
<ValidationMessage For="#(() => model.OtherReason)" />
There is also a select that has the list of available Reason objects, one of which is Other.
I do have a property called OtherReasonRequired which graphically does what I want (either Enable or Disable the input based on if the selected Reason == "Other") so that code works:
public bool OtherReasonRequired
{
get
{
var result = false;
if (model.ReasonId > 0)
{
var reason = Reasons.Find(x => x.Id == model.ReasonId);
result = reason.Reason == "Other";
}
return result;
}
}
This works perfectly if I select Other and give OtherReason a value, the Save/Submit button is valid and it works.
My issue is when I have NOT selected Other. Graphically, the InputField does get disabled and grayed out. But the Save/Submit believes the model is invalid because there is no value in the OtherReason field.
Is there something I can do to get this to work?
Would love to have a dynamic attribute called RequiredIf.
But logically to me, I see this as a bug. If a control is disabled, it's value is irrelevant in my mind.

Answer 1

Please check the following. I don't use any of the built-in Data Annotation, but it's still very easy to check the input and let the user know what I want them to do:
<EditForm Model="#DisplayModel" OnValidSubmit="HandleValidSubmit" >
<InputRadioGroup TValue=int? #bind-Value=DisplayModel.ReasonID>
#for (int i=1; i< Reasons.Count(); i++){
<InputRadio Value=Reasons[i].ID /> #Reasons[i].Description <br/>
}
<InputRadio Value=0 />Other <br/>
</InputRadioGroup>
<input #bind=DisplayModel.OtherText disabled=#((DisplayModel.ReasonID??1) !=0 ) />
<button type="submit">Submit</button>
<div class="text-danger">#DisplayMessage</div>
</EditForm>
#code {
string DisplayMessage="";
class Reason { public int? ID; public string? Description; }
List<Reason> Reasons = new List<Reason> {
new Reason { ID = 0, Description = "Other"},
new Reason { ID = 1, Description = "You're lame" },
new Reason { ID = 2, Description = "I'm too busy" }
};
class MyDisplayModel
{
public int? ReasonID;
public string OtherText="";
}
MyDisplayModel DisplayModel = new MyDisplayModel();
private async Task HandleValidSubmit()
{
if(DisplayModel.ReasonID is not null) if (DisplayModel.ReasonID==0) if (DisplayModel.OtherText == "")
{
DisplayMessage = "You must type a description of your issue.";
StateHasChanged();
await Task.Delay(1500);
DisplayMessage = "";
}
}
}