嵌套if语句（nested if statements）

在F＃编程中嵌套if/then或if/then/else语句总是合法的，这意味着你可以在另一个if或else if语句中使用if或else if语句。

语法 (Syntax)

if expr then
   expr
   if expr then
      expr
   else
      expr
else
   expr

例子 (Example)

let a : int32 = 100
let b : int32 = 200
(* check the boolean condition using if statement *)
if (a = 100) then
(* if condition is true then check the following *)
   if (b = 200) then
      printfn "Value of a is 100 and b is 200\n"
printfn "Exact value of a is: %d" a
printfn "Exact value of b is: %d" b

编译并执行程序时，它会产生以下输出 -

Value of a is 100 and b is 200
Exact value of a is: 100
Exact value of b is: 200