Understanding ValidationContext in DataAnnotations

I want to utilize Validator.TryValidateValue() but don't understand the mechanics. Say, i have the following:

public class User {
    [Required(AllowEmptyStrings = false)]
    [StringLength(6)]
    public string Name { get; set; }
}

and the method:

public void CreateUser(string name) {...}

My validation code is:

ValidationAttribute[] attrs = bit of reflection here to populate from User class
var ctx = new ValidationContext(name, null, null);
var errors = new List<ValidationResult>();
bool valid = Validator.TryValidateValue(name, ctx, errors, attrs);

It works fine until value of name is null. I'm getting ArgumentNullException when instantiating ValidationContext and don't understand why. TryValidateValue() also demands non-null context. I have a value and a list of attributes to validate against. What is that ValidationContext for?