What's wrong with this boolean iteration?

While doing this bool iteration, I was tempted to use the non existing operator ||=, and figured there must be a simpler or better design that would replace its valid use (rather than think it's just "missing"):

bool validExtension = false;

foreach (string extension in Plugin.Extensions)
{
    validExtension = validExtension || Path.GetExtension(file).Equals(extension.TrimStart('*'), StringComparison.InvariantCultureIgnoreCase);

    if (validExtension)
    {
        break;
    }
}

importButton.Enabled = File.Exists(importTextBox.Text) 开发者_StackOverflow社区&& validExtension;

That loop has an invariant: on entry to the body, validExtension = false.

So the body can be simplified to:

if (validExtension = Path.GetExtension(file).Equals(extension.TrimStart('*'), StringComparison.InvariantCultureIgnoreCase))
    break;

If there wasn't such an invariant, you could use the compound assignment operator |= if you always wanted to evaluate the right-hand side, or if (!lhs) lhs = rhs; if you wanted short-circuiting.

foreach (string extension in Plugin.Extensions)
{
     if (Path.GetExtension(file).Equals(extension.TrimStart('*'), StringComparison.InvariantCultureIgnoreCase))
     {
          validExtension = true;
          break;
     }
}

This works because you are breaking the first time you find a valid extension, so validExtension is always false on the first line of the loop.

can't you just say validExtension = Path.Get.... since at the start of the expression validExtension will always be false.

While there is no ||= operator in C#, there is the |= operator that may be what you're looking for. MSDN Reference

If its a string[], the whole code can be changed like this

Func<string[], string, bool> validExtension = (arr, s) => arr.Contains(s);
importButton.Enabled = validExtension(Plugin.Extensions, Path.GetExtension(file)) && File.Exists(importTextBox.Text);

For checking a value inside an Array you could always use Array.Contains extension method.
P.S: I have reversed the tests as Ben Voigt rightfully said