get next value in A..Z range using two lambdas, one Func<char> variable

A_Z_cycle.cs

static public class A_Z_cycle
{
    static public Func<char> Next = () => {
        const char a='A', b='Z', c=(char)(b-a+1); 
        int n=-1;
        return (Next=(()=>(char)(a + (n=(n+1)%c))))();
    };
}