找到一个带有 Reflection 的私有字段?
-
01-07-2019 - |
题
鉴于这门课
class Foo
{
// Want to find _bar with reflection
[SomeAttribute]
private string _bar;
public string BigBar
{
get { return this._bar; }
}
}
我想找到我将用属性标记的私有项目 _bar。那可能吗?
我已经对属性进行了此操作,我在其中查找了属性,但从未查找私有成员字段。
我需要设置哪些绑定标志来获取私有字段?
解决方案
使用 BindingFlags.NonPublic
和 BindingFlags.Instance
旗帜
FieldInfo[] fields = myType.GetFields(
BindingFlags.NonPublic |
BindingFlags.Instance);
其他提示
您可以像使用属性一样执行此操作:
FieldInfo fi = typeof(Foo).GetField("_bar", BindingFlags.NonPublic | BindingFlags.Instance);
if (fi.GetCustomAttributes(typeof(SomeAttribute)) != null)
...
使用反射获取私有变量的值:
var _barVariable = typeof(Foo).GetField("_bar", BindingFlags.NonPublic | BindingFlags.Instance).GetValue(objectForFooClass);
使用反射设置私有变量的值:
typeof(Foo).GetField("_bar", BindingFlags.NonPublic | BindingFlags.Instance).SetValue(objectForFoocClass, "newValue");
其中 objectForFooClass 是类类型 Foo 的非 null 实例。
在反映私有成员时需要注意的一件事是,如果您的应用程序在中等信任度下运行(例如,当您在共享托管环境上运行时),它不会找到它们 - BindingFlags.NonPublic 选项将被忽略。
typeof(MyType).GetField("fieldName", BindingFlags.NonPublic | BindingFlags.Instance)
带有扩展方法的良好语法
您可以使用如下代码访问任意类型的任何私有字段:
Foo foo = new Foo();
string c = foo.GetFieldValue<string>("_bar");
为此,您需要定义一个扩展方法来为您完成工作:
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);
}
}
我个人使用这个方法
if (typeof(Foo).GetFields(BindingFlags.NonPublic | BindingFlags.Instance).Any(c => c.GetCustomAttributes(typeof(SomeAttribute), false).Any()))
{
// do stuff
}
是的,但是您需要设置绑定标志来搜索私有字段(如果您正在寻找类实例之外的成员)。
您需要的绑定标志是:System.Reflection.BindingFlags.NonPublic
以下是一些简单获取和设置私有字段和属性(带有 setter 的属性)的扩展方法:
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
代码:
/// <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;
}
}
我在谷歌搜索时发现了这个,所以我意识到我正在碰触旧帖子。但是 GetCustomAttributes 需要两个参数。
typeof(Foo).GetFields(BindingFlags.NonPublic | BindingFlags.Instance)
.Where(x => x.GetCustomAttributes(typeof(SomeAttribute), false).Length > 0);
第二个参数指定是否要搜索继承层次结构
不隶属于 StackOverflow