如何突破名单 <T> .ForEach（）从C＃中的if语句中循环

Question

I would like to skip an iteration of a List<T>.ForEach() loop from within an if statement.

I have the code:

        instructions.ForEach(delegate(Instruction inst)
        {                
            if (!File.Exists(inst.file))
            {
                continue; // Jump to next iteration
            }

            Console.WriteLine(inst.file);
        });

However the compiler states there is nothing to jump out from (presumably as it seems to take the if block as the enclosing block?).

Is there anyway to do the above? Something like parentblock.continue; etc.

Thanks

Answer 1

Use a return statement instead of continue . Remember that by using the ForEach extension method, you are executing a function for each item, the body of which is specified between { and }. By exiting the function it will just continue with the next value from the list.

Answer 2

ForEach in this case is just a method executing a delegate for every item in the list. It is not a looping control structure so continue cannot appear there. Rewrite it as a normal foreach loop:

foreach (var inst in instructions) {
    if (!File.Exists(inst.file))
    {
        continue; // Jump to next iteration
    }

    Console.WriteLine(inst.file);
}

Answer 3

Use LINQ's Where clause to apply the predicate from the onset

foreach(Instruction inst in instructions.Where(i => File.Exists(i.file))){
    Console.WriteLine(inst.file);
}

Answer 4

The delegate that is sent to the ForEach function will run once per item in the instructions list. For it to skip one item just return from the delegate function.

    instructions.ForEach(delegate(Instruction inst)
    {                
        if (!File.Exists(inst.file))
        {
            return; // Jump to next iteration
        }

        Console.WriteLine(inst.file);
    });