使用C＃中的反射从字符串获取属性值

我正在尝试在代码中使用Reflection ¹示例实现数据转换。

GetSourceValue函数具有比较各种类型的开关，但是我想删除这些类型和属性，并让GetSourceValue仅使用单个字符串作为参数来获取属性的值。我想在字符串中传递类和属性，并解析该属性的值。

这可能吗？

^1个_{原始博客文章的Web存档版本}

#1楼

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

当然，您将需要添加验证等功能，但这就是要点。

#2楼

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 incompatiblereturn (T) retval;
}

这将允许您使用单个字符串进入属性，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。

#3楼

您永远不会提及要检查的对象，并且由于您拒绝引用给定对象的对象，因此我假设您的意思是静态对象。

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，我用局部变量obj标记了要检查的obj 。 null表示静态，否则将其设置为所需的值。还请注意， GetEntryAssembly()是获取“运行中”程序集的几种可用方法之一，如果在加载类型时遇到困难，则可能需要使用它。

#4楼

使用Microsoft.VisualBasic命名空间（ Microsoft.VisualBasic.dll ）的CallByName怎么办？它使用反射来获取常规对象，COM对象甚至动态对象的属性，字段和方法。

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

然后

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

#5楼

使用System.Reflection命名空间的PropertyInfo。无论我们尝试访问什么属性，反射都可以编译。该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;}

获得对象的Location属性效果很好

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

我们将获得Location：{X = 71，Y = 27}我们也可以以相同的方式返回location.X或location.Y。

#6楼

更短的方法....

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());

#7楼

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，您可以用作：

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

#8楼

这是查找嵌套属性的另一种方法，该属性不需要字符串即可告诉您嵌套路径。将单一属性方法归功于Ed S.。

    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);}

#9楼

以下代码是一种递归方法，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。此方法在该线程中使用上面的AlexD的GetPropertyValue()答案的简化版本。由于有了这个讨论线程，我得以弄清楚该如何做！

例如，通过使用如下方法，我使用此方法来显示WebService响应中所有属性的爆炸或转储：

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 = falseforeach (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 objectobject myPropertyValue = GetPropertyValue(parentObj, pi.Name);if (myPropertyValue == null){// Instance of Property does not existif (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 ValueConsole.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 valueConsole.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);}}
}

#10楼

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

#11楼

关于嵌套属性的讨论，如果使用如下所示的DataBinder.Eval Method (Object, String) ，则可以避免所有反射：

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

当然，您需要添加对System.Web程序集的引用，但这可能没什么大不了的。

#12楼

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;}

这是一种在列表中获取所有属性及其值的方法。

#13楼

jheddings和AlexD都就如何解析属性字符串写了出色的答案。我想把我的东西混在一起，因为我正是为此目的编写了一个专用的库。

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。

因此，例如，如果您有一个像这样的对象

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

并想要获取Property2 ，您可以这样：

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

这是它可以解析的路径的最基本示例。如果您想了解它的其他功能或扩展方法，请转到Github页面。

#14楼

如果我使用Ed S的代码，我会得到

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

似乎Xamarin.Forms中没有GetProperty() 。 TargetFrameworkProfile是Profile7在我的便携式类库（.NET框架4.5，Windows 8中，ASP.NET 1.0的核心，Xamarin.Android，Xamarin.iOS，Xamarin.iOS经典）。

现在我找到了一个可行的解决方案：

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));return property?.GetValue(source);
}

资源

#15楼

调用方法已在.NET Standard（自1.6版）中更改。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);
}

#16楼

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);
}

#17楼

这是我的解决方案。它也可以与COM对象一起使用，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;
}

#18楼

public class YourClass
{//Add below line in your classpublic 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"];

#19楼

以下方法最适合我：

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); }}
}

要获取属性值：

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

设置属性值：

t1["prop1"] = value;

#20楼

看看Heleonix.Reflection库。您可以通过路径获取/设置/调用成员，或者创建比反射更快的getter / setter（lambda编译为委托）。例如：

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

或一次创建一个吸气剂并缓存以备重用（这具有更高的性能，但如果中间成员为null，则可能会抛出NullReferenceException）：

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

或者，如果您要创建具有不同getter的List<Action<object, object>> ，只需为编译的委托指定基本类型（类型转换将添加到编译的lambda中）：

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

#21楼

这是我根据其他答案得到的。在错误处理方面变得如此具体有些过大的杀伤力。

public static T GetPropertyValue<T>(object sourceInstance, string targetPropertyName, bool throwExceptionIfNotExists = false)
{string errorMsg = null;try{if (sourceInstance == null || string.IsNullOrWhiteSpace(targetPropertyName)){errorMsg = $"Source object is null or property name is null or whitespace. '{targetPropertyName}'";Log.Warn(errorMsg);if (throwExceptionIfNotExists)throw new ArgumentException(errorMsg);elsereturn default(T);}Type returnType = typeof(T);Type sourceType = sourceInstance.GetType();PropertyInfo propertyInfo = sourceType.GetProperty(targetPropertyName, returnType);if (propertyInfo == null){errorMsg = $"Property name '{targetPropertyName}' of type '{returnType}' not found for source object of type '{sourceType}'";Log.Warn(errorMsg);if (throwExceptionIfNotExists)throw new ArgumentException(errorMsg);elsereturn default(T);}return (T)propertyInfo.GetValue(sourceInstance, null);}catch(Exception ex){errorMsg = $"Problem getting property name '{targetPropertyName}' from source instance.";Log.Error(errorMsg, ex);if (throwExceptionIfNotExists)throw;}return default(T);
}

#22楼

jheddings的好答案。我想对其进行改进，以允许引用聚合数组或对象集合，以便propertyName可以为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.propertystring[] propertyNameParts = propertyName.Split('.');foreach (string propertyNamePart in propertyNameParts){if (obj == null)    return null;// propertyNamePart could contain reference to specific // element (by index) inside a collectionif (!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 indexint indexStart = propertyNamePart.IndexOf("[")+1;string collectionPropertyName = propertyNamePart.Substring(0, indexStart-1);int collectionElementIndex = Int32.Parse(propertyNamePart.Substring(indexStart, propertyNamePart.Length-indexStart-1));//   get collection objectPropertyInfo pi = obj.GetType().GetProperty(collectionPropertyName);if (pi == null) return null;object unknownCollection = pi.GetValue(obj, null);//   try to process the collection as arrayif (unknownCollection.GetType().IsArray){object[] collectionAsArray = unknownCollection as object[];obj = collectionAsArray[collectionElementIndex];}else{//   try to process the collection as IListSystem.Collections.IList collectionAsList = unknownCollection as System.Collections.IList;if (collectionAsList != null){obj = collectionAsList[collectionElementIndex];}else{// ??? Unsupported collection type}}}}return obj;}