Validation attribute for list<string>

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C#

Windows

Hi,

I am getting an errors that Model.IsValid == false.

Here is one of the property with an error:

// Property

[RegularExpression(@"^[0-9]*$", ErrorMessage = "Invalid number")]
public List<string> Numbers { get; set; }

//Constructor

public ClassName()
{
 Numbers  = new List<string>();
}

Can someone explain me why? Do I need to validate each element of the List? How to achieve it?

What I have tried:

I tried to debug the problem and searched google but didn't find anything usefully.