语句

示例

语句列表和块语句

static void Main() {
    F();
    G();
    {
        H();
        I();
    }
}

标记语句和 goto 语句

static void Main(string[] args) {
    if (args.Length == 0)
        goto done;
    Console.WriteLine(args.Length);

done:
    Console.WriteLine("Done");
}

局部常数声明

static void Main() {
    const float pi = 3.14f;
    const int r = 123;
    Console.WriteLine(pi * r * r);
}

局部变量声明

static void Main() {
    int a;
    int b = 2, c = 3;
    a = 1;
    Console.WriteLine(a + b + c);
}

表达式语句

static int F(int a, int b) {
    return a + b;
}

static void Main() {
    F(1, 2);  // Expression statement
}

if 语句

static void Main(string[] args) {
    if (args.Length == 0)
        Console.WriteLine("No args");
    else
        Console.WriteLine("Args");
}

switch 语句

static void Main(string[] args) {
    switch (args.Length) {
        case 0:
            Console.WriteLine("No args");
            break;
        case 1:
            Console.WriteLine("One arg ");
            break;
        default:
            int n = args.Length;
            Console.WriteLine("{0} args", n);
            break;
    }
}

while 语句

static void Main(string[] args) {
    int i = 0;
    while (i < args.Length) {
        Console.WriteLine(args[i]);
        i++;
    }
}

do 语句

static void Main() {
    string s;
    do { s = Console.ReadLine(); }
    while (s != "Exit");
}

for 语句

static void Main(string[] args) {
    for (int i = 0; i < args.Length; i++)
        Console.WriteLine(args[i]);
}

foreach 语句

static void Main(string[] args) {
    foreach (string s in args)
        Console.WriteLine(s);
}

break 语句

static void Main(string[] args) {
    int i = 0;
    while (true) {
        if (i == args.Length)
            break;
        Console.WriteLine(args[i++]);
    }
}

continue 语句

static void Main(string[] args) {
    int i = 0;
    while (true) {
       Console.WriteLine(args[i++]);
       if (i < args.Length)
            continue;
       break;
    }
}

return 语句

static int F(int a, int b) {
    return a + b;
}

static void Main() {
    Console.WriteLine(F(1, 2));
    return;
}

throw 语句和 try 语句

static int F(int a, int b) {
    if (b == 0)
        throw new Exception("Divide by zero");
    return a / b;
}

static void Main() {
    try {
        Console.WriteLine(F(5, 0));
    }
    catch(Exception e) {
        Console.WriteLine("Error");
    }
}

checked 和 unchecked 语句

static void Main() {
    int x = Int32.MaxValue;

    Console.WriteLine(x + 1);      // Overflow

    checked {
        Console.WriteLine(x + 1);  // Exception
    }    

    unchecked {
        Console.WriteLine(x + 1);  // Overflow
    }
}

lock 语句

static void Main() {
    A a = ...;
    lock(a) {
        a.P = a.P + 1;
    }
}

using statements

static void Main() {
    using (Resource r = new Resource()) {
        r.F();
    }
}