We have a Ticket class which implements IValidatableObject. It contains IEnumerable<ValidationResult> Validate(ValidationContext validationContext) method which performs object validation based on the private _action property.

If _action is ETicketAction.Create, assignee must be null; if action is ETicketAction.Edit, assignee must not be null. Besides these rules, we want to validate some common Ticket fields (ProductLineId, ProductVersion). For this prupose, we implemented private ValidateCommonFields method which is called from both create and edit actions.

public partial class Ticket : IValidatableObject
{
    public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
    {
        if (string.IsNullOrEmpty(Summary))
        {
            yield return new ValidationResult("Summary must be set!");
        }
        
        if (_action == (int)ETicketAction.Create)
        {
            if (Assignee != null)
            {
                yield return new ValidationResult("Assignee must be null when creating a ticket!");
            }
            
            ValidateCommonFields();
        }
        else if (_action == (int)ETicketAction.Edit)
        {
            if (Assignee == null)
            {
                yield return new ValidationResult("Assignee must be set when editing a ticket!");
            }
            
            ValidateCommonFields();
        }
        else if (_action == (int)ETicketAction.Close)
        {
            // ...
        }
    }

    private IEnumerable<ValidationResult> ValidateCommonFields()
    {
        if (ProductLineId == null)
        {
            yield return new ValidationResult("Product line must be set!");
        }

        if (ProductVersion.IsNullOrEmpty())
        {
            yield return new ValidationResult($"Product version must be set!");
        }
    }
}

Debugger reaches the line where it calls ValidateCommonFields(), but it never steps inside the function. We placed a breakpoint inside ValidateCommonFields, but it is never hit. Both ProductLineId and ProductVersion are null, but the ValidationResults inside ValidateCommonFields are not returned.

I assume it has something to do with the yield statements. Should I use yield return ValidateCommonFields() when calling the common validation method?