How to make a property required based on multiple condition?

Question

I have a list of Pair of radio buttons (Yes/No): ``` Q1.(Y)(N) Q2.(Y)(N) Q3.(Y)(N) Q4.(Y)(N) ``` and I have one property in my model `public string MedicalExplanation { get; set; }` My goal is to make Explanation required if any of the radio button has been set to true. My first try was to use `[Required]` but it does not handle conditions. Then I decided to use third party tool like MVC Foolproof Validation I used it like this: `[RequiredIf("Q1", true, ErrorMessage = "You must explain any \"Yes\" answers!")]` Now the problem is I don't know how to make it required if any of the other Q2, Q3, Q4 is checked. Please advice

Accepted Answer

In your ViewModel, create a bool property like this:

```
public bool IsMedicalExplanationRequired
{
   get
   {
       return Q1 || Q2 || Q3 || Q4;
   }
}
```

Then, use your `RequiredIf` attribute like this:

```
[RequiredIf("IsMedicalExplanationRequired", true, ErrorMessage = "You must explain any \"Yes\" answers!")]
```

UPDATE:

If your Q1 - Q4 properties are of type `bool?`, just change the `IsMedicalExplanationRequired` property like below:

```
public bool IsMedicalExplanationRequired
{
   get
   {
       return Q1.GetValueOrDefault() || Q2.GetValueOrDefault() || Q3.GetValueOrDefault() || Q4.GetValueOrDefault();
   }
}
```

How to make a property required based on multiple condition?

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