关于c＃：使用Reflection查找私有字段？

Find a private field with Reflection?

鉴于这门课程

1
2
3
4
5
6
7
8
9
10
11

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_bar。那可能吗？

我已经用我寻找属性的属性做了这个，但从来没有私有成员字段。

获取私有字段需要设置哪些绑定标志？

使用BindingFlags.NonPublic和BindingFlags.Instance标志

1
2
3

FieldInfo[] fields = myType.GetFields(
BindingFlags.NonPublic |
BindingFlags.Instance);

您可以像使用属性一样执行此操作：

1
2
3

FieldInfo fi = typeof(Foo).GetField("_bar", BindingFlags.NonPublic | BindingFlags.Instance);
if (fi.GetCustomAttributes(typeof(SomeAttribute)) != null)
...

使用Reflection获取私有变量的值：

1	var _barVariable = typeof(Foo).GetField("_bar", BindingFlags.NonPublic \| BindingFlags.Instance).GetValue(objectForFooClass);

使用Reflection设置私有变量的值：

1	typeof(Foo).GetField("_bar", BindingFlags.NonPublic \| BindingFlags.Instance).SetValue(objectForFoocClass,"newValue");

其中objectForFooClass是类类型Foo的非null实例。

反思私有成员时需要注意的一件事是，如果您的应用程序以中等信任的方式运行(例如，当您在共享托管环境中运行时)，它将无法找到它们 - BindingFlags.NonPublic选项将被忽略。

1	typeof(MyType).GetField("fieldName", BindingFlags.NonPublic \| BindingFlags.Instance)

带扩展方法的漂亮语法

您可以使用以下代码访问任意类型的任何私有字段：

1 2	Foo foo = new Foo(); string c = foo.GetFieldValue<string>("_bar");

为此，您需要定义一个可以为您完成工作的扩展方法：

1
2
3
4
5
6
7
8

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);
}
}

我亲自使用这种方法

1
2
3
4

if (typeof(Foo).GetFields(BindingFlags.NonPublic | BindingFlags.Instance).Any(c => c.GetCustomAttributes(typeof(SomeAttribute), false).Any()))
{
// do stuff
}

以下是一些简单的get和set私有字段和属性(带有setter的属性)的扩展方法：

用法示例：

1
2
3
4
5
6
7
8
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

码：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92

/// <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，但是您需要设置Binding标志来搜索私有字段(如果您在类实例之外寻找成员)。

您需要的绑定标志是：System.Reflection.BindingFlags.NonPublic

我在谷歌上搜索这个时遇到了这个，所以我意识到我碰到了一个旧帖子。但是GetCustomAttributes需要两个参数。