分配運算子
賦值運算子 = 將左手運算元的值設定為右手運算元的值，並返回該值：
int a = 3; // assigns value 3 to variable a
int b = a = 5; // first assigns value 5 to variable a, then does the same for variable b
Console.WriteLine(a = 3 + 4); // prints 7
賦值運算子 = 將左手運算元的值設定為右手運算元的值，並返回該值：
int a = 3; // assigns value 3 to variable a
int b = a = 5; // first assigns value 5 to variable a, then does the same for variable b
Console.WriteLine(a = 3 + 4); // prints 7