validation service

ValidationService.cs

public class ValidationService : IValidationService
{
    private BindableBase bindableBase;
    private object ruleCollection;
    private MethodInfo methodInfo;

    public event EventHandler<ValidationResultArgs> PropertyInvalid;

    public RuleCollection<VM> For<VM>(VM bindableBase) where VM : BindableBase
    {
        this.bindableBase = bindableBase;
        ruleCollection = new RuleCollection<VM>();
        bindableBase.PropertyChanged += BindableBase_PropertyChanged;
        var type = typeof(RuleCollection<VM>);
        methodInfo = type.GetMethod(nameof(RuleCollection<BindableBase>.GetRules));
        return (RuleCollection<VM>)ruleCollection;
    }
    
    // was ruleCollection.GetRules()
    private List<IValidationRule> GetRules()
    {
        var returnValue = methodInfo.Invoke(ruleCollection, null);
        return (List<IValidationRule>)returnValue;
    }
    ...
}


public class RuleCollection<VM> where VM : BindableBase
{
    private readonly List<IValidationRule> validationRuleList = new List<IValidationRule>();

    public RuleCollection<VM> AddRule<T>(Expression<Func<VM, object>> expression, params ValidationRule<T>[] rules)
    {
        var propertyName = expression.GetMemberName();
        return AddRule(propertyName, rules);
    }
    ...