CheckDynamicUmbracoProperties.cs

public static class CheckDynamicUmbracoProperties<T>
{
    public static T SelectFirstPropertyValueOfGivenAlias(IPublishedContent ChildPage, string PropertyTypeAlias)
    {
        var query = ((Dictionary<string, IPublishedProperty>
              .ValueCollection)ChildPage.Properties)
              .Where(x => x.PropertyTypeAlias == PropertyTypeAlias)
              .Select(x => x.Value).Cast<T>()
              .FirstOrDefault();

        return query;
    }
}