c# - 如何修复错误 CS1738 命名参数规范必须在指定所有固定参数后出现

Question

public static Mutex CreateMutex(){
    MutexAccessRule rule = new MutexAccessRule(new SecurityIdentifier(WellKnownSidType.WorldSid, null), MutexRights.FullControl, AccessControlType.Allow);
    MutexSecurity mutexSecurity = new MutexSecurity();
    mutexSecurity.AddAccessRule(rule);
    bool createdNew;
    return new Mutex(initiallyOwned: false,"Global\\E475CED9-78C4-44FC-A2A2-45E515A2436", out createdNew,mutexSecurity);
}

Error CS1738 Named argument specifications must appear after all fixed arguments have been specified

Answer 1

所以引用 C# Doc

Named arguments, when used with positional arguments, are valid as long

• as they're not followed by any positional arguments

所以这就是原因，为什么你会遇到编译错误。

使用 C# 7.2 及更高版本时，它说:

Named arguments, when used with positional arguments, are valid as long

• as they're used in the correct position.

有关更多信息，请参阅:
Named and Optional Arguments

所以如果我们看一下 constructor :

public Mutex (bool initiallyOwned,
              string name,
              out bool createdNew,
              System.Security.AccessControl.MutexSecurity mutexSecurity);

我们将看到在您的情况下，位置的顺序是正确的。
如果您要切换到 C# 7.2 或更高版本，您的代码将被编译。

但是对于较低版本，您有两种选择:

删除 initiallyOwned 的参数命名

对所有参数使用命名参数

喜欢:

return new Mutex(initiallyOwned: false,
                 name: "Global\E475CED9-78C4-44FC-A2A2-45E515A2436",
                 createdNew: out createdNew,
                 mutexSecurity: mutexSecurity); 

使用第二个选项时，命名参数的位置不再重要。