C# 设置私有字段的值
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Set value of private field
提问by Tono Nam
Why is the following code not working:
为什么以下代码不起作用：
class Program
{
static void Main ( string[ ] args )
{
SomeClass s = new SomeClass( );
s.GetType( ).GetField( "id" , System.Reflection.BindingFlags.NonPublic ) // sorry reasently updated to GetField from GetProperty...
.SetValue( s , "new value" );
}
}
class SomeClass
{
object id;
public object Id
{
get
{
return id;
}
}
}
I am trying to set the value of a private field.
我正在尝试设置私有字段的值。
Here is the exeption I get:
这是我得到的例外：
System.NullReferenceException was unhandled Message=Object reference not set to an instance of an object. Source=ConsoleApplication7
StackTrace:
at Program.Main(String[] args) in C:\Users\Antonio\Desktop\ConsoleApplication7\ConsoleApplication7\Program.cs:line 18
at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart() InnerException:
采纳答案by nick_w
Try this (inspired by Find a private field with Reflection?):
试试这个（灵感来自Find a private field with Reflection?）：
var prop = s.GetType().GetField("id", System.Reflection.BindingFlags.NonPublic
| System.Reflection.BindingFlags.Instance);
prop.SetValue(s, "new value");
My changes were to use the GetFieldmethod - you are accessing a field and not a property, and to or NonPublicwith Instance.
我的更改是使用该GetField方法 - 您正在访问一个字段而不是一个属性，并且NonPublic使用Instance.
回答by Alxandr
Evidently, adding BindingFlags.Instanceseems to have solved it:
显然，添加BindingFlags.Instance似乎已经解决了它：
> class SomeClass
{
object id;
public object Id
{
get
{
return id;
}
}
}
> var t = typeof(SomeClass)
;
> t
[Submission#1+SomeClass]
> t.GetField("id")
null
> t.GetField("id", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);
> t.GetField("id", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance)
[System.Object id]
>
