c# - 在调用方方法中检索原始变量/参数名称(类似于 [CallerMemberName] 属性)

Question

有没有办法在调用方方法中获取变量/参数的原始名称？在某种程度上，它就像 [CallerMemberName]属性，但对于变量/参数。

更新 2018.02: 这个问题与这些问题类似:1 , 2和 3 ，但到 2018 年初仍没有有效的标准化解决方案。建议的解决方案:使用 Expression<Func<T>>可以有 non-documented effects 并且非常 CPU 密集型，因为将代码转换为表达式以仅获取变量的原始名称并不是一个简单的操作。这就像创建一个 1М 大小的空数组来存储单个整数而不是简单的整数——非常无效 («з гармати по горобцям»)。

简短示例:

int ComplexMathMethod(int startPos, int endPos,
    int backgroundStartPos, int backgroundEndStart, 
    int squareStartPos, // …and other positions… )
{
    CheckPosition(startPos);
    CheckPosition(endPos);
    CheckPosition(backgroundStartPos);
    CheckPosition(backgroundEndStart);
    CheckPosition(squareStartPos);
    // …and so on…  
}

void CheckPosition(int position)
{
    bool isValidPosition = // complex check;
    if (!isValidPosition)
    {
        throw new ArgumentException(nameof(position));

        // --->>> It will be extremely convenient to automatically replace "nameof(position)" with original 
        // name of variable/argument from caller method, like: "startPos", "endPos", "backgroundStartPos", etc.

        // Additional string argument with original variable name is not a good solution too.
        // Because, I have similar "check" method that checks 4 connected position’s integers at once.
        // Therefore, 4 input ints with additional +4 string arguments will make a mess.
    }
}

---

长示例:

void ShowMessage(string messageStr)
{

    // Problem: get original variable/argument name, as it was called, in the caller method.
    string callerMethodArgName;

    // If method was called from "Main" method, than callerMethodArgName should equal to "finishMsg".
    // If method was called from "DoWork" method, than callerMethodArgName should equal to "taskName".
    // If method was called from "StartProgram" method, than callerMethodArgName should equal to "startingMsg".    

    // …missing logic, reflection code, etc.

    // The next line is just a stub.
    callerMethodArgName = nameof(messageStr);

    Console.WriteLine($"Variable name is \"{callerMethodArgName}\"; value is \"{messageStr}\".");

}

void Main()
{
    StartProgram();
    DoWork("Programming…");

    // Example 1.
    string finishMsg = "Finish!";
    ShowMessage(finishMsg);
}

// Example, caller method 2.
void StartProgram()
{
    string startingMsg = "Starting program";
    ShowMessage(startingMsg);
}

// Example, caller method 3.
void DoWork(string taskName)
{
    ShowMessage(taskName);
}

当前程序输出:

// Variable name is "messageStr"; value is "Starting program".
// Variable name is "messageStr"; value is "Programming…".
// Variable name is "messageStr"; value is "Finish!".

要求/期望的输出:

// Variable name is "startingMsg"; value is "Starting program".
// Variable name is "taskName"; value is "Programming…".
// Variable name is "finishMsg"; value is "Finish!".

我不确定这是否可能。我花了几个小时玩反射，但不幸的是，它没有结果。这在实际项目调试时会非常方便。

Answer 1

您可以为此使用 Linq.Expressions。首先，您需要像这样更改 CheckPosition 的签名:

void CheckPosition(Expression<Func<int>> positionExpression)

之后你可以这样调用它:

CheckPosition(() => startPos);

完整代码:

int ComplexMathMethod(int startPos, int endPos,
    int backgroundStartPos, int backgroundEndStart,
    int squareStartPos) // …and other positions… )
{
    CheckPosition(() => startPos);
    CheckPosition(() => endPos);
    CheckPosition(() => backgroundStartPos);
    CheckPosition(() => backgroundEndStart);
    CheckPosition(() => squareStartPos);
    // …and so on…  

    return 0;
}

void CheckPosition(Expression<Func<int>> positionExpression)
{
    var name = ((MemberExpression) positionExpression.Body).Member.Name;
    var value = positionExpression.Compile().Invoke();

    Console.WriteLine($"Name = {name}, value ={value}");
}