Validate a list in a custom validation attribute

Question

Using a custom validation attribute, I'm trying to validate a list of objects. The class is shown below: MyClass . In the custom attribute, I'm able to covert object value into a list of objects, but how can I access the properties, Id and Name within objects?

I understand I could put the attribute directly on the the MyClass properties, but I need to check a couple things before validation. First, I need to check if the number of items in the list is greater than one. Then, if the count is greater than one, I need to check if both Id and Name are null.

My thought is that it would be easier to validate the entire list in one Attribute. However even if I did place the attributes on the MyClass properties, I still need to access the values within the list.

If the list is passed as the value parameter of IsValid then all list items would be within value. If I put the attributes on the MyClass properties I would need to get the values another way. I've been able to get single values with the code below, but I'm unable to get a list of values.

Bottom line: I need a way to access all the values within a list either from the object value parameter or the ValidationContext validationContext parameter.

Getting a single value (not a list of values):

var property = validationContext.ObjectType.GetProperty("MyProperty");
var value = property.GetValue(validationContext.ObjectInstance, null);

Custom Attribute:

public sealed class ValidateNewSauList : ValidationAttribute
{
    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        var myList = value as IList;
    } 
}

Here is the User defined class:

public class MyClass
{
    public int Id { get; set; }
    public string Name { get; set; }
}

Answer 1

The business logic is a bit unclear, so, based on just a qualified guess, the solution could be as following. Assuming that you have a _lst = List<MyClass> , then you can iterate through the list and apply your validation rules (eg referred to as methods ValidateID() and ValidateName() ) to both properties:

foreach (MyClass _mc in _lst)
{
   ValidateID (_mc.Id);
   ValidateName (_mc.Name);

}

Hope this may help. Best regards,