C# - 带有 if 语句的 Foreach 循环

Question

How can I go about doing this so if the "if" statement is true, to skip the code below the foreach loop and to go on with the rest of the program

void()
{
    foreach()
    {
        if()
        {

        }
    }

    //code I want to skip if "if" statement is true

}

Answer 1

There's no way to directly do what you want (without "goto" labels -- perish the thought!), but you can use the "break" keyword, and set a variable you can refer to later.

void()
{
    var testWasTrue = false;
    foreach()
    {
        if()
        {
            testWasTrue = true;
            break;  // break out of the "foreach"
        }
    }

    if( !testWasTrue ) {
        //code I want to skip if "if" statement is true
    }

}

Answer 2

I know this was already answered, but I figured I'd throw in my 2 cents since nobody considered abstracting the check to a separate method:

void()
{
    if (ShouldDoStuff(myCollection))
        DoStuff(myCollection);
    else
        DoOtherStuff(myCollection);
}

private bool ShouldDoStuff(collection)
{
    foreach()
    {
        if ()
            return true;
    }
    return false;
}

This provides a much cleaner code at the higher level for dealing with your algorithms and removes all the clutter discussed about. It cleanly separates the tasks in void() of checking and performing the actions and readers instantly know exactly what the program flow is without having to discern what they're doing with a boolean or break logic lurking about. No single method has more than 1 responsibility or task.

Yeah, it's possible the poster wants to do other work in their foreach, but that's an entirely different discussion and not what was described in their question. If you simply want to check if the given collection (or object) satisfies a certain condition, that check can be moved to a separate method. Even leaves the door open for automated unit tests for all three components.

Even if DoStuff and DoOtherStuff are not abstracted to their own methods, it provides nicer readability and logical flow.

Answer 3

The 'break' keyword will break out of the loop.

foreach (someClass a in someArray) 
{
  if(a.someProperty) // bool property 
  {
    //Stuff to do if that condition is true
    doSomethingElse();
    //Calling the break keyword will stop the loop and jump immediately outside of it
    break;
  }
  //Other code to run for each iteration of the loop
}

//Here is where execution will pick up either after break is called or after the loop finishes

Answer 4

void()
{
     bool process = true;
     foreach()
     {
          if()
          {
              process = false;
              break;
          }
     }

     if (process)
     {
       //code I want to skip if "if" statement is true
     }

}

Answer 5

As was mentioned in my comment you may do this through extra bool variable.

void()
    {
        bool positiveResult; // by default it gets false value
        foreach()
        {
            if()
            {
                positiveResult = true;
                // you may use "break" to skip the loop
                break;
            }
        }

        if( !positiveResult  ) 
         {
            //code I want to skip if "if" statement is true
         }

    }

Answer 6

void() 
{ 
    bool skip = false;
    foreach() 
    { 
        if() 
        { 
           skip = true;
        } 
    } 

    if(!skip)
    {
        //code I want to skip if "if" statement is true 
    }
} 

Answer 7

Only way I know how is a bool flag.

void()
{
  bool x = false;
  foreach()
  {
    if()
    {
      x = true;
      break;
    }
  }
  if(!x)
  {
    //Code to skip if "if" statement is true.
  }
}

Not super elegant, but easy. Edit: beat by 12 secs :)

Answer 8

If the collection you are iterating through contains The IEnumerable Interface, You could use Any() with a Lambda!

int[] myArray = { 1, 2, 3 };

                if( myArray.Any((a) => a == 1) )
                {
                    return;
                }

It is read: if my array contains any value a where a is equal to 1, then return out of this function.

Plus if you want to make it harder to read, you can omit the curly braces/brackets.

if( myArray.Any((a) => a == 1) )
     return;