[Solved] C# MemoryCache Changing Data by Itself

Change:

Utility.CacheHelper.SaveTocache("MyKey",a);

to:

Utility.CacheHelper.SaveTocache("MyKey",a.ToList());

and:

List<String> b = Utility.CacheHelper.GetFromCache<List<String>>("MyKey");

to:

List<String> b = Utility.CacheHelper.GetFromCache<List<String>>("MyKey").ToList();

Technically just the latter change is required – the former will make it even more bulletproof.

This is necessary since if any entries adding to the MemoryCache will be shared amongst callers – so if one caller manipulates the List then other callers will also see that manipulated list.

By calling ToList you ensure that each caller gets its own copy of the List – so items added to one won’t be seen in the other.