使用反射獲取元組的值

Question

所以我試圖使用反射來獲取元組的值，唯一的問題是我得到了一個異常：System.Reflection.TargetInvocationException。 我已經嘗試按照此處建議的一條評論獲取其值： Casting to a Tuple<object,object> , var itemX = t.GetProperty("ItemX").GetValue(data); 如果我使用 lem.FieldType.GetProperty("Item1").Name ，我可以將名稱恢復為 Item1, Item2 等...，我是否正確使用它還是有其他方法？

FieldInfo[] fields = this.GetType().GetFields(BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.Public | BindingFlags.Static | BindingFlags.FlattenHierarchy);
FieldInfo[] tuples = fields.Where(field=>typeof(IStructuralEquatable).IsAssignableFrom(field.FieldType) && typeof(IStructuralComparable).IsAssignableFrom(field.FieldType)).ToArray();

Debug.WriteLine(tuples.Length.ToString()" ->");
foreach (var elem in tuples)
{
    Debug.WriteLine(elem.FieldType.GetProperty("Item1").GetValue(this,null).ToString());

    PropertyInfo[] info = elem.FieldType.GetProperties();
    Debug.WriteLine(info[0].GetValue(this,null).ToString());
    for(int i=0;i<info.Length;i++)
    {
        Debug.WriteLine(info[i].GetValue(this,null).ToString());
    }

還有我的元組：

protected Tuple<string,int, int, int> testTuple = new Tuple<string, int, int, int>("Test",1,0,1);

Answer 1

讓我們查詢tuple的Item1..ItemN屬性； 我們可以借助Linq和正則表達式來完成，例如

  using System.Linq;
  using System.Reflection;
  using System.Text.RegularExpressions;

  ...

  Dictionary<string, object> result = testTuple
    .GetType()
    .GetProperties()
    .Where(prop => prop.CanRead)
    .Where(prop => !prop.GetIndexParameters().Any())
    .Where(prop => Regex.IsMatch(prop.Name, "^Item[0-9]+$"))
    .ToDictionary(prop => prop.Name, prop => prop.GetValue(testTuple));

是時候將它包裝到您的方法中了：

  ...
  foreach (var tuple in tuples) {
    var result = tuple
      .GetType()
      .GetProperties()
      .Where(prop => prop.CanRead)
      .Where(prop => !prop.GetIndexParameters().Any())
      .Where(prop => Regex.IsMatch(prop.Name, "^Item[0-9]+$"))
      .Select(prop => new {
         name  = prop.Name,
         value = prop.GetValue(tuple), 
       });

    foreach (var item in result)
      Debug.WriteLine($"{item.name} = {item.value}");
  }
  ...

編輯：讓我們從獲取Tuple<,...,>類型的所有字段開始（請參閱下面的評論）：

  Object objectToInspect = this;

  HashSet<Type> typleTypes = new HashSet<Type>() {
    typeof(Tuple<>),
    typeof(Tuple<,>),
    typeof(Tuple<,,>),
    typeof(Tuple<,,,>),
    typeof(Tuple<,,,,>),
    typeof(Tuple<,,,,,>),
    typeof(Tuple<,,,,,,>),
    typeof(Tuple<,,,,,,,>),
  };

  var fieldsWithTuples = objectToInspect
    .GetType()
    .GetFields(BindingFlags.NonPublic |
               BindingFlags.Instance |
               BindingFlags.Public |
               BindingFlags.Static |
               BindingFlags.FlattenHierarchy)
    .Where(field => field.FieldType.IsGenericType)
    .Where(field => typleTypes.Contains(field.FieldType.GetGenericTypeDefinition()))
    .Select(field => new {
      name  = field.Name,
      value = field.GetValue(field.IsStatic
                 ? null                     // we should provide null for static
                 : objectToInspect)
    })
    .Where(item => item.value != null);
 // .Select(item => item.value) // if you want tuple values
 // .ToArray();                 // materialized as an array

現在我們准備好使用我上面的代碼：

  foreach (var tuple in fieldsWithTuples.Select(f => f.value)) {
    var result = tuple
      .GetType()
      .GetProperties()
      .Where(prop => prop.CanRead)
      .Where(prop => !prop.GetIndexParameters().Any())
      .Where(prop => Regex.IsMatch(prop.Name, "^Item[0-9]+$"))
      .Select(prop => new {
         name  = prop.Name,
         value = prop.GetValue(tuple), 
       });

    foreach (var item in result)
      Debug.WriteLine($"{item.name} = {item.value}");
  }

Answer 2

元組的定義如下： Tuple<T1,T2,T3,T4,T5,T6,T7,TRest> 。

遵循元組內的值數量，其邏輯不同，因此要在所有情況下（即使有 8 個項目或更多）通過反射讀取元組，只需使用這段代碼（通用編碼）：

    public IEnumerable<object> EnumerateValueTuple(object valueTuple)
    {
        var tuples = new Queue<object>();
        tuples.Enqueue(valueTuple);

        while (tuples.Count > 0 && tuples.Dequeue() is object tuple)
        {
            foreach (var field in tuple.GetType().GetFields())
            {
                if (field.Name == "Rest")
                    tuples.Enqueue(field.GetValue(tuple));
                else
                    yield return field.GetValue(tuple);
            }
        }
    }

你可以使用：

var item = (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11);

foreach(var value in EnumerateValueTuple(item))
  Console.Out.WriteLine(value); // Prints "1 2 3 4 5 6 7 8 9 10 11"