Possible to store references to objects in list?

C# doesn't have a concept of "ref locals" (the CLR does though). So you'll need to wrap the values in a reference type that you can mutate. For example,

public class Ref<T> where T : struct
{
    public T Value {get; set;}
}

List<Ref<int>> intRefList = new List<Ref<int>>();
var myIntRef = new Ref<int> { Value = 1 };
intRefList.Add(myIntRef);

Console.WriteLine(myIntRef.Value);//1

Console.WriteLine(intRefList[0].Value);//1

myIntRef.Value = 2;

Console.WriteLine(intRefList[0].Value);//2

Edit: C# 7.0 added ref locals but they still can't be used in this way because you can't put ref locals into an array or list.

No, this is not possible in C#.

C# does not support references to local variables, which includes references to elements of local containers.

The only way to obtain a true reference in C# (that is, not an instance of a reference type, but an actual reference to another variable) is via the ref or out parameter keywords. Those keywords cannot be used with any sort of indexed value or property, which includes elements in a List<>. You also have no direct control over these references: the compiler performs the dereferencing for you, behind the scenes.

Interestingly, the CLR does support this kind of reference; if you decompile CIL into C# you will sometimes see types like int& that are references to int. C# purposely does not allow you to use these types directly in your code.