Upcasting and downcasting in C#

Upcasting converts an object of a specialized type to a more general type

Downcasting converts an object from a general type to a more specialized type

BankAccount    ba1,
                   ba2 =   new BankAccount("John", 250.0M, 0.01);
    LotteryAccount la1,
                   la2 =   new LotteryAccount("Bent", 100.0M);

    ba1 = la2;                    // upcasting   - OK
//  la1 = ba2;                    // downcasting - Illegal 
                                  //   discovered at compile time
//  la1 = (LotteryAccount)ba2;    // downcasting - Illegal
                                  //   discovered at run time
    la1 = (LotteryAccount)ba1;    // downcasting - OK 
                                  //   ba1 already refers to a LotteryAccount