如何在C＃IF语句中使用此示例“ return”？

Question

The sample I want to use is from This SO article .

public static bool HasWritePermissionOnDir(string path)
{
    var writeAllow = false;
    var writeDeny = false;
    var accessControlList = Directory.GetAccessControl(path);
    if (accessControlList == null)
        return false;
    var accessRules = accessControlList.GetAccessRules(true, true, typeof(System.Security.Principal.SecurityIdentifier));
    if (accessRules == null)
        return false;

    foreach (FileSystemAccessRule rule in accessRules)
    {
        if ((FileSystemRights.Write & rule.FileSystemRights) != FileSystemRights.Write) continue;

        if (rule.AccessControlType == AccessControlType.Allow)
            writeAllow = true;
        else if (rule.AccessControlType == AccessControlType.Deny)
            writeDeny = true;
    }

    return writeAllow && !writeDeny;
}

How can I use the "return writeAllow && !writeDeny" in an If statement? Or can I even do that. Sorry if this is a dumb question, but in my limited experience I haven't see a return look like that.

Answer 1

Is this what you mean by "using it in an if-statement"??

if (HasWritePermissionOnDir(mypath))
{
    // Then write a new file to the directory
}

This code calls the function with mypath , and based on the returned result (which boils down to writeAllow && !writeDeny ), it may or may not evaluate to true and execute the if-statement.

Answer 2

At the end of the method, the boolean value is evaluated and returned in one line. But you could rewrite it like this (not recommended, just showing for clarity):

bool ValueToReturn = WriteAllow && !writeDeny;
return ValueToReturn;

Or if you think about it in plain English:

Return true if write is allowed and not denied.

The double ampersand ( & ) is a logical short-circuit meaning (in this case) that if the first term evaluates to false, it won't matter if the second term does or not, so it won't be evaluated.

Answer 3

writeAllow && !writeDeny eavluates to a bool . The only requirement for an if statement is that whatever is inside the parentheses evaluates to a bool . So using the expression inside of an if statement is as simple as:

if (writeAllow && !writeDeny)
{
    //do something
}

Answer 4

The && operator is a boolean operator, meaning it returns either true or false. That means you can use this expression in an if statement exactly the way it is:

if (writeAllow && !writeDeny)

will work.

Answer 5

If I understand, you want to take this code and put it inside one of your own functions. Is that correct?

Firstly, I suggest you leave it as a separate function. It makes it easier to discern when that piece of code is meant to do. You can use it in an if statement with:

if (HasWritePermissionOnDir("C:\\My\\Path"))
{
    // TODO
}

Or if you insist on copying the code inline:

// TODO: Content of HasWritePermissionOnDir method without the return statement...
if (WriteAllow && !writeDeny)
{
    // TODO
}