I made a
static partial class Utils
First of all a
Utils class with many methods tends to become a huge pile of much unrelated code. Because nearly all "Helper" methods will be placed there. By dividing them into single files you fight against a symptom and not againt the root cause. You'll transform the pile of code into a pile of files.
You should cluster the methods into topics and divide the Utils class in meaningful units. Please keep an eye on the Single Responsibility Principle.