如何退出 C# 中的 foreach 循环？

Question

foreach (var name in parent.names)
{
    if name.lastname == null)
    {
        Violated = true;
        this.message = "lastname reqd";
    }

    if (!Violated)
    {
        Violated = !(name.firstname == null) ? false : true;
        if (ruleViolated)
            this.message = "firstname reqd";
    }
}

Whenever violated is true, I want to get out of the foreach loop immediately. How do I do it?

Answer 1

Use break .

---

Unrelated to your question, I see in your code the line:

Violated = !(name.firstname == null) ? false : true;

In this line, you take a boolean value (name.firstname == null) . Then, you apply the ! operator to it. Then, if the value is true, you set Violated to false; otherwise to true. So basically, Violated is set to the same value as the original expression (name.firstname == null) . Why not use that, as in:

Violated = (name.firstname == null);

Answer 2

只需使用以下语句：

break;

Answer 3

使用break关键字。

Answer 4

Look at this code, it can help you to get out of the loop fast!

foreach (var name in parent.names)
{
   if (name.lastname == null)
   {
      Violated = true;
      this.message = "lastname reqd";
      break;
   }
   else if (name.firstname == null)
   {
      Violated = true;
      this.message = "firstname reqd";
      break;
   }
}

Answer 5

During testing I found that foreach loop after break go to the loop beging and not out of the loop. So I changed foreach into for and break in this case work correctly- after break program flow goes out of the loop.

Answer 6

break; - to exit foreach

continue; - jump to next value

Answer 7

Instead of foreach loop

foreach (var name in parent.names)
{
    if name.lastname == null)
    {
        Violated = true;
        this.message = "lastname reqd";
    }

    if (!Violated)
    {
        Violated = !(name.firstname == null) ? false : true;
        if (ruleViolated)
            this.message = "firstname reqd";
    }
}

make use of equivalent for loop

bool Violated = false;

for (int i = 0; i < parent.names.Count && !Violated; i++)
{
    var name = parent.names[i];
    
    if name.lastname == null)
    {
        Violated = true;
        this.message = "lastname reqd";
    }

    if (!Violated)
    {
        Violated = !(name.firstname == null) ? false : true;
        if (ruleViolated)
            this.message = "firstname reqd";
    }
}

With the condition i < parent.names.Count && !Violated you get full control to stop the loop safe without any break or return or whatever to brutally force the foreach to stop.