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[英]Use reflection to find a private field within `this` class, and instantiate it
[英]Find a private field with Reflection?
鑒於這個類
class Foo
{
// Want to find _bar with reflection
[SomeAttribute]
private string _bar;
public string BigBar
{
get { return this._bar; }
}
}
我想找到我將用屬性標記的私有項目 _bar。 那可能嗎?
我已經在我尋找屬性的屬性中完成了此操作,但從未尋找私有成員字段。
我需要設置哪些綁定標志來獲取私有字段?
使用BindingFlags.NonPublic
和BindingFlags.Instance
標志
FieldInfo[] fields = myType.GetFields(
BindingFlags.NonPublic |
BindingFlags.Instance);
您可以像使用屬性一樣執行此操作:
FieldInfo fi = typeof(Foo).GetField("_bar", BindingFlags.NonPublic | BindingFlags.Instance);
if (fi.GetCustomAttributes(typeof(SomeAttribute)) != null)
...
使用反射獲取私有變量的值:
var _barVariable = typeof(Foo).GetField("_bar", BindingFlags.NonPublic | BindingFlags.Instance).GetValue(objectForFooClass);
使用反射設置私有變量的值:
typeof(Foo).GetField("_bar", BindingFlags.NonPublic | BindingFlags.Instance).SetValue(objectForFoocClass, "newValue");
其中 objectForFooClass 是類類型 Foo 的非空實例。
您可以使用如下代碼訪問任意類型的任何私有字段:
Foo foo = new Foo();
string c = foo.GetFieldValue<string>("_bar");
為此,您需要定義一個可以為您完成工作的擴展方法:
public static class ReflectionExtensions {
public static T GetFieldValue<T>(this object obj, string name) {
// Set the flags so that private and public fields from instances will be found
var bindingFlags = BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance;
var field = obj.GetType().GetField(name, bindingFlags);
return (T)field?.GetValue(obj);
}
}
在考慮私有成員時需要注意的一件事是,如果您的應用程序以中等信任度運行(例如,當您在共享托管環境中運行時),它將找不到它們—— BindingFlags.NonPublic 選項將被忽略。
typeof(MyType).GetField("fieldName", BindingFlags.NonPublic | BindingFlags.Instance)
我個人使用這種方法
if (typeof(Foo).GetFields(BindingFlags.NonPublic | BindingFlags.Instance).Any(c => c.GetCustomAttributes(typeof(SomeAttribute), false).Any()))
{
// do stuff
}
下面是一些用於簡單獲取和設置私有字段和屬性(帶有 setter 的屬性)的擴展方法:
用法示例:
public class Foo { private int Bar = 5; } var targetObject = new Foo(); var barValue = targetObject.GetMemberValue("Bar");//Result is 5 targetObject.SetMemberValue("Bar", 10);//Sets Bar to 10
代碼:
/// <summary>
/// Extensions methos for using reflection to get / set member values
/// </summary>
public static class ReflectionExtensions
{
/// <summary>
/// Gets the public or private member using reflection.
/// </summary>
/// <param name="obj">The source target.</param>
/// <param name="memberName">Name of the field or property.</param>
/// <returns>the value of member</returns>
public static object GetMemberValue(this object obj, string memberName)
{
var memInf = GetMemberInfo(obj, memberName);
if (memInf == null)
throw new System.Exception("memberName");
if (memInf is System.Reflection.PropertyInfo)
return memInf.As<System.Reflection.PropertyInfo>().GetValue(obj, null);
if (memInf is System.Reflection.FieldInfo)
return memInf.As<System.Reflection.FieldInfo>().GetValue(obj);
throw new System.Exception();
}
/// <summary>
/// Gets the public or private member using reflection.
/// </summary>
/// <param name="obj">The target object.</param>
/// <param name="memberName">Name of the field or property.</param>
/// <returns>Old Value</returns>
public static object SetMemberValue(this object obj, string memberName, object newValue)
{
var memInf = GetMemberInfo(obj, memberName);
if (memInf == null)
throw new System.Exception("memberName");
var oldValue = obj.GetMemberValue(memberName);
if (memInf is System.Reflection.PropertyInfo)
memInf.As<System.Reflection.PropertyInfo>().SetValue(obj, newValue, null);
else if (memInf is System.Reflection.FieldInfo)
memInf.As<System.Reflection.FieldInfo>().SetValue(obj, newValue);
else
throw new System.Exception();
return oldValue;
}
/// <summary>
/// Gets the member info
/// </summary>
/// <param name="obj">source object</param>
/// <param name="memberName">name of member</param>
/// <returns>instanse of MemberInfo corresponsing to member</returns>
private static System.Reflection.MemberInfo GetMemberInfo(object obj, string memberName)
{
var prps = new System.Collections.Generic.List<System.Reflection.PropertyInfo>();
prps.Add(obj.GetType().GetProperty(memberName,
System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Instance |
System.Reflection.BindingFlags.FlattenHierarchy));
prps = System.Linq.Enumerable.ToList(System.Linq.Enumerable.Where( prps,i => !ReferenceEquals(i, null)));
if (prps.Count != 0)
return prps[0];
var flds = new System.Collections.Generic.List<System.Reflection.FieldInfo>();
flds.Add(obj.GetType().GetField(memberName,
System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance |
System.Reflection.BindingFlags.FlattenHierarchy));
//to add more types of properties
flds = System.Linq.Enumerable.ToList(System.Linq.Enumerable.Where(flds, i => !ReferenceEquals(i, null)));
if (flds.Count != 0)
return flds[0];
return null;
}
[System.Diagnostics.DebuggerHidden]
private static T As<T>(this object obj)
{
return (T)obj;
}
}
是的,但是您需要設置綁定標志來搜索私有字段(如果您在類實例之外尋找成員)。
您需要的綁定標志是:System.Reflection.BindingFlags.NonPublic
我在谷歌上搜索這個時遇到了這個,所以我意識到我正在撞一個舊帖子。 但是 GetCustomAttributes 需要兩個參數。
typeof(Foo).GetFields(BindingFlags.NonPublic | BindingFlags.Instance)
.Where(x => x.GetCustomAttributes(typeof(SomeAttribute), false).Length > 0);
第二個參數指定是否要搜索繼承層次結構
如果您的 .Net 框架大於 4.5。 您可以使用 GetRuntimeFields 方法。
此方法返回在指定類型上定義的所有字段,包括繼承、非公共、實例和靜態字段。
var foo = new Foo();
var fooFields = foo.GetType().GetRuntimeFields()
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