提问



我正在尝试使用我的代码中的Reflection 1 示例实现数据转换。[51]


GetSourceValue函数有一个开关比较各种类型,但我想删除这些类型和属性,并GetSourceValue只使用一个字符串作为参数获取属性的值。我想在字符串中传递一个类和属性并解析属性的值。


这可能吗?


1 原始博客文章的Web档案版 [52]

最佳参考


 public static object GetPropValue(object src, string propName)
 {
     return src.GetType().GetProperty(propName).GetValue(src, null);
 }


当然,你会想要添加验证和诸如此类的东西,但这就是它的要点。

其它参考1


这样的事情怎么样:


public static Object GetPropValue(this Object obj, String name) {
    foreach (String part in name.Split('.')) {
        if (obj == null) { return null; }

        Type type = obj.GetType();
        PropertyInfo info = type.GetProperty(part);
        if (info == null) { return null; }

        obj = info.GetValue(obj, null);
    }
    return obj;
}

public static T GetPropValue<T>(this Object obj, String name) {
    Object retval = GetPropValue(obj, name);
    if (retval == null) { return default(T); }

    // throws InvalidCastException if types are incompatible
    return (T) retval;
}


这将允许您使用单个字符串下降到属性,如下所示:


DateTime now = DateTime.Now;
int min = GetPropValue<int>(now, "TimeOfDay.Minutes");
int hrs = now.GetPropValue<int>("TimeOfDay.Hours");


您可以将这些方法用作静态方法或扩展。

其它参考2


添加到任何Class:


public class Foo
{
    public object this[string propertyName]
    {
        get { return this.GetType().GetProperty(propertyName).GetValue(this, null); }
        set { this.GetType().GetProperty(propertyName).SetValue(this, value, null); }
    }

    public string Bar { get; set; }
}


然后,您可以使用as:


Foo f = new Foo();
// Set
f["Bar"] = "asdf";
// Get
string s = (string)f["Bar"];

其它参考3


如何使用Microsoft.VisualBasic命名空间Microsoft.VisualBasic.dllCallByName?它使用反射来获取普通对象,COM对象甚至动态对象的属性,字段和方法。[53]


using Microsoft.VisualBasic;
using Microsoft.VisualBasic.CompilerServices;


接着


Versioned.CallByName(this, "method/function/prop name", CallType.Get).ToString();

其它参考4


jheddings的答案很棒。我想改进它,允许引用聚合数组或对象集合,以便propertyName可以是property1.property2 [[X]] .property3:


    public static object GetPropertyValue(object srcobj, string propertyName)
    {
        if (srcobj == null)
            return null;

        object obj = srcobj;

        // Split property name to parts (propertyName could be hierarchical, like obj.subobj.subobj.property
        string[] propertyNameParts = propertyName.Split('.');

        foreach (string propertyNamePart in propertyNameParts)
        {
            if (obj == null)    return null;

            // propertyNamePart could contain reference to specific 
            // element (by index) inside a collection
            if (!propertyNamePart.Contains("["))
            {
                PropertyInfo pi = obj.GetType().GetProperty(propertyNamePart);
                if (pi == null) return null;
                obj = pi.GetValue(obj, null);
            }
            else
            {   // propertyNamePart is areference to specific element 
                // (by index) inside a collection
                // like AggregatedCollection[123]
                //   get collection name and element index
                int indexStart = propertyNamePart.IndexOf("[")+1;
                string collectionPropertyName = propertyNamePart.Substring(0, indexStart-1);
                int collectionElementIndex = Int32.Parse(propertyNamePart.Substring(indexStart, propertyNamePart.Length-indexStart-1));
                //   get collection object
                PropertyInfo pi = obj.GetType().GetProperty(collectionPropertyName);
                if (pi == null) return null;
                object unknownCollection = pi.GetValue(obj, null);
                //   try to process the collection as array
                if (unknownCollection.GetType().IsArray)
                {
                    object[] collectionAsArray = unknownCollection as Array[];
                    obj = collectionAsArray[collectionElementIndex];
                }
                else
                {
                    //   try to process the collection as IList
                    System.Collections.IList collectionAsList = unknownCollection as System.Collections.IList;
                    if (collectionAsList != null)
                    {
                        obj = collectionAsList[collectionElementIndex];
                    }
                    else
                    {
                        // ??? Unsupported collection type
                    }
                }
            }
        }

        return obj;
    }

其它参考5


关于嵌套属性讨论,如果使用DataBinder.Eval Method (Object, String)如下所示,可以避免所有反射内容:[54]


var value = DataBinder.Eval(DateTime.Now, "TimeOfDay.Hours");


当然,你需要添加对System.Web程序集的引用,但这可能不是什么大问题。

其它参考6


如果我使用Ed S的代码,我得到



  ReflectionExtensions.GetProperty(Type,string)由于其保护级别而无法访问



似乎GetProperty()在Xamarin.Forms中不可用。 TargetFrameworkProfile在我的可移植类库(.NET Framework 4.5,Windows 8,ASP.NET Core 1.0,Xamarin.Android,Xamarin.iOS,Xamarin.iOS Classic)中是Profile7


现在我找到了一个有效的方案:


using System.Linq;
using System.Reflection;

public static object GetPropValue(object source, string propertyName)
{
    var property = source.GetType().GetRuntimeProperties().FirstOrDefault(p => string.Equals(p.Name, propertyName, StringComparison.OrdinalIgnoreCase));
    if(property != null)
    {
        return property.GetValue(source);
    }
    return null;
}


[56]

其它参考7


使用 System.Reflection 命名空间的PropertyInfo。无论我们尝试访问什么属性,反射都可以很好地编译。错误将在运行时出现。


    public static object GetObjProperty(object obj, string property)
    {
        Type t = obj.GetType();
        PropertyInfo p = t.GetProperty("Location");
        Point location = (Point)p.GetValue(obj, null);
        return location;
    }


它可以正常获取对象的Location属性


Label1.Text = GetObjProperty(button1, "Location").ToString();


我们将获得位置:{X=71,Y=27}
我们也可以以同样的方式返回location.X或location.Y。

其它参考8


public static List<KeyValuePair<string, string>> GetProperties(object item) //where T : class
    {
        var result = new List<KeyValuePair<string, string>>();
        if (item != null)
        {
            var type = item.GetType();
            var properties = type.GetProperties(BindingFlags.Public | BindingFlags.Instance);
            foreach (var pi in properties)
            {
                var selfValue = type.GetProperty(pi.Name).GetValue(item, null);
                if (selfValue != null)
                {
                    result.Add(new KeyValuePair<string, string>(pi.Name, selfValue.ToString()));
                }
                else
                {
                    result.Add(new KeyValuePair<string, string>(pi.Name, null));
                }
            }
        }
        return result;
    }


这是一种在List中获取其值的所有属性的方法。

其它参考9


调用方法在.NET Standard中发生了变化(截至1.6)。我们也可以使用C#6的空条件运算符。


using System.Reflection; 
public static object GetPropValue(object src, string propName)
{
    return src.GetType().GetRuntimeProperty(propName)?.GetValue(src);
}

其它参考10


下面是另一种查找嵌套属性的方法,该属性不需要字符串告诉您嵌套路径。请注意Ed S.的单一属性方法。


    public static T FindNestedPropertyValue<T, N>(N model, string propName) {
        T retVal = default(T);
        bool found = false;

        PropertyInfo[] properties = typeof(N).GetProperties();

        foreach (PropertyInfo property in properties) {
            var currentProperty = property.GetValue(model, null);

            if (!found) {
                try {
                    retVal = GetPropValue<T>(currentProperty, propName);
                    found = true;
                } catch { }
            }
        }

        if (!found) {
            throw new Exception("Unable to find property: " + propName);
        }

        return retVal;
    }

        public static T GetPropValue<T>(object srcObject, string propName) {
        return (T)srcObject.GetType().GetProperty(propName).GetValue(srcObject, null);
    }

其它参考11


你永远不会提到你正在检查的对象,因为你拒绝那些引用给定对象的对象,我会认为你的意思是静态的。


using System.Reflection;
public object GetPropValue(string prop)
{
    int splitPoint = prop.LastIndexOf('.');
    Type type = Assembly.GetEntryAssembly().GetType(prop.Substring(0, splitPoint));
    object obj = null;
    return type.GetProperty(prop.Substring(splitPoint + 1)).GetValue(obj, null);
}


请注意,我使用局部变量obj标记了正在检查的对象。 null表示静态,否则将其设置为您想要的。另请注意,GetEntryAssembly()是获得运行程序集的几种可用方法之一,如果您在加载类型时遇到困难,可能需要使用它。

其它参考12


下面的代码是一个递归方法,用于显示对象实例中包含的所有属性名称和值的整个层次结构。此方法在此线程中使用上面AlexD的GetPropertyValue()答案的简化版本。感谢这个讨论主题,我能够弄清楚如何做到这一点!


例如,我使用此方法通过调用方法显示WebService响应中所有属性的爆炸或转储,如下所示:



  PropertyValues_byRecursion("Response", response, false);



public static object GetPropertyValue(object srcObj, string propertyName)
{
  if (srcObj == null) 
  {
    return null; 
  }
  PropertyInfo pi = srcObj.GetType().GetProperty(propertyName.Replace("[]", ""));
  if (pi == null)
  {
    return null;
  }
  return pi.GetValue(srcObj);
}

public static void PropertyValues_byRecursion(string parentPath, object parentObj, bool showNullValues)
{
  /// Processes all of the objects contained in the parent object.
  ///   If an object has a Property Value, then the value is written to the Console
  ///   Else if the object is a container, then this method is called recursively
  ///       using the current path and current object as parameters

  // Note:  If you do not want to see null values, set showNullValues = false

  foreach (PropertyInfo pi in parentObj.GetType().GetTypeInfo().GetProperties())
  {
    // Build the current object property's namespace path.  
    // Recursion extends this to be the property's full namespace path.
    string currentPath = parentPath + "." + pi.Name;

    // Get the selected property's value as an object
    object myPropertyValue = GetPropertyValue(parentObj, pi.Name);
    if (myPropertyValue == null)
    {
      // Instance of Property does not exist
      if (showNullValues)
      {
        Console.WriteLine(currentPath + " = null");
        // Note: If you are replacing these Console.Write... methods callback methods,
        //       consider passing DBNull.Value instead of null in any method object parameters.
      }
    }
    else if (myPropertyValue.GetType().IsArray)
    {
      // myPropertyValue is an object instance of an Array of business objects.
      // Initialize an array index variable so we can show NamespacePath[idx] in the results.
      int idx = 0;
      foreach (object business in (Array)myPropertyValue)
      {
        if (business == null)
        {
          // Instance of Property does not exist
          // Not sure if this is possible in this context.
          if (showNullValues)
          {
            Console.WriteLine(currentPath  + "[" + idx.ToString() + "]" + " = null");
          }
        }
        else if (business.GetType().IsArray)
        {
          // myPropertyValue[idx] is another Array!
          // Let recursion process it.
          PropertyValues_byRecursion(currentPath + "[" + idx.ToString() + "]", business, showNullValues);
        }
        else if (business.GetType().IsSealed)
        {
          // Display the Full Property Path and its Value
          Console.WriteLine(currentPath + "[" + idx.ToString() + "] = " + business.ToString());
        }
        else
        {
          // Unsealed Type Properties can contain child objects.
          // Recurse into my property value object to process its properties and child objects.
          PropertyValues_byRecursion(currentPath + "[" + idx.ToString() + "]", business, showNullValues);
        }
        idx++;
      }
    }
    else if (myPropertyValue.GetType().IsSealed)
    {
      // myPropertyValue is a simple value
      Console.WriteLine(currentPath + " = " + myPropertyValue.ToString());
    }
    else
    {
      // Unsealed Type Properties can contain child objects.
      // Recurse into my property value object to process its properties and child objects.
      PropertyValues_byRecursion(currentPath, myPropertyValue, showNullValues);
    }
  }
}

其它参考13


public class YourClass
{
    //Add below line in your class
    public object this[string propertyName] => GetType().GetProperty(propertyName)?.GetValue(this, null);
    public string SampleProperty { get; set; }
}

//And you can get value of any property like this.
var value = YourClass["SampleProperty"];

其它参考14


Dim NewHandle As YourType = CType(Microsoft.VisualBasic.CallByName(ObjectThatContainsYourVariable, "YourVariableName", CallType), YourType)

其它参考15


更短的方式....


var a = new Test { Id = 1 , Name = "A" , date = DateTime.Now};
var b = new Test { Id = 1 , Name = "AXXX", date = DateTime.Now };

var compare = string.Join("",a.GetType().GetProperties().Select(x => x.GetValue(a)).ToArray())==
              string.Join("",b.GetType().GetProperties().Select(x => x.GetValue(b)).ToArray());

其它参考16


jheddings和AlexD都写了关于如何解析属性字符串的优秀答案。我想把它扔进混合物中,因为我专门为此目的写了一个专用的库。


Pather.CSharp 的主要类是Resolver。默认情况下,它可以解析属性,数组和字典条目。[59]


所以,例如,如果你有这样的对象


var o = new { Property1 = new { Property2 = "value" } };


并想得到Property2,你可以这样做:


IResolver resolver = new Resolver();
var path = "Property1.Property2";
object result = r.Resolve(o, path); 
//=> "value"


这是它可以解决的路径的最基本的例子。如果你想看看它还能做什么,或者你如何扩展它,只需前往它的Github页面。[60]

其它参考17


public static TValue GetFieldValue<TValue>(this object instance, string name)
{
    var type = instance.GetType(); 
    var field = type.GetFields(BindingFlags.NonPublic | BindingFlags.Static | BindingFlags.Instance).FirstOrDefault(e => typeof(TValue).IsAssignableFrom(e.FieldType) && e.Name == name);
    return (TValue)field?.GetValue(instance);
}

public static TValue GetPropertyValue<TValue>(this object instance, string name)
{
    var type = instance.GetType();
    var field = type.GetProperties(BindingFlags.NonPublic | BindingFlags.Static | BindingFlags.Instance).FirstOrDefault(e => typeof(TValue).IsAssignableFrom(e.PropertyType) && e.Name == name);
    return (TValue)field?.GetValue(instance);
}

其它参考18


这是我的解决方案。它也适用于COM对象,并允许从COM对象访问集合/数组项。


public static object GetPropValue(this object obj, string name)
{
    foreach (string part in name.Split('.'))
    {
        if (obj == null) { return null; }

        Type type = obj.GetType();
        if (type.Name == "__ComObject")
        {
            if (part.Contains('['))
            {
                string partWithoundIndex = part;
                int index = ParseIndexFromPropertyName(ref partWithoundIndex);
                obj = Versioned.CallByName(obj, partWithoundIndex, CallType.Get, index);
            }
            else
            {
                obj = Versioned.CallByName(obj, part, CallType.Get);
            }
        }
        else
        {
            PropertyInfo info = type.GetProperty(part);
            if (info == null) { return null; }
            obj = info.GetValue(obj, null);
        }
    }
    return obj;
}

private static int ParseIndexFromPropertyName(ref string name)
{
    int index = -1;
    int s = name.IndexOf('[') + 1;
    int e = name.IndexOf(']');
    if (e < s)
    {
        throw new ArgumentException();
    }
    string tmp = name.Substring(s, e - s);
    index = Convert.ToInt32(tmp);
    name = name.Substring(0, s - 1);
    return index;
}

其它参考19


以下方法对我来说非常适合:


class MyClass {
    public string prop1 { set; get; }

    public object this[string propertyName]
    {
        get { return this.GetType().GetProperty(propertyName).GetValue(this, null); }
        set { this.GetType().GetProperty(propertyName).SetValue(this, value, null); }
    }
}


要获得属性值:


MyClass t1 = new MyClass();
...
string value = t1["prop1].ToString();


要设置属性值:


t1["prop1] = value;

其它参考20


看看Heleonix.Reflection库。您可以通过路径获取/设置/调用成员,或者创建一个比反射更快的getter/setter(lambda编译成委托)。例如:[61]


var success = Reflector.Get(DateTime.Now, null, "Date.Year", out int value);


或者创建一个getter并缓存以供重用(这样性能更高但如果中间成员为null,则可能抛出NullReferenceException):


var getter = Reflector.CreateGetter<DateTime, int>("Date.Year", typeof(DateTime));
getter(DateTime.Now);


或者,如果要创建List<Action<object, object>>不同的getter,只需为已编译的委托指定基类型(类型转换将添加到已编译的lambda中):


var getter = Reflector.CreateGetter<object, object>("Date.Year", typeof(DateTime));
getter(DateTime.Now);