vb.net 如何使用属性本身获取属性的名称
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How do you get the name of a property using the property itself
提问by Lykeuhfox
I've run into an issue where I need to get the name of a property for logging purposes. I'm sure there is a way to do this in VB.Net using some amalgam of reflection and lambda expressions, but I've been unsuccessful so far.
我遇到了一个问题，我需要获取属性的名称以进行记录。我确信在 VB.Net 中有一种方法可以使用反射和 lambda 表达式的一些混合来做到这一点，但到目前为止我一直没有成功。
What I'm trying to do is convert this:
我想要做的是转换这个：
objAddress.AddressLine
to this:
对此：
"AddressLine"
回答by Obsidian Phoenix
In the past, I've used a method I found online for doing this with INotifyPropertyChanged. I can't remember exactly where, but this details the same resolution:
过去，我使用了一种在网上找到的方法来使用INotifyPropertyChanged. 我不记得确切的位置，但这详细说明了相同的分辨率：
http://paulstovell.com/blog/strong-property-names
http://paulstovell.com/blog/strong-property-names
C#
C＃
public class Test : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private string _Name;
public string Name
{
get { return _Name; }
set
{
_Name = value;
RaisePropertyChanged(() => Name);
}
}
private void RaisePropertyChanged(Expression<Func<object>> property)
{
MemberExpression exp = property.Body as MemberExpression;
if (exp != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(exp.Member.Name));
}
}
}
VB
VB
Public Class Test
Implements INotifyPropertyChanged
Public Event PropertyChanged(sender As Object, e As PropertyChangedEventArgs) Implements INotifyPropertyChanged.PropertyChanged
Private _Name As String
Public Property Name() As String
Get
Return _Name
End Get
Set(value As String)
_Name = value
RaisePropertyChanged(Function() Me.Name)
End Set
End Property
Private Sub RaisePropertyChanged(Of T)(propertyName As Expression(Of Func(Of T)))
Dim exp As MemberExpression = TryCast(propertyName.Body, MemberExpression)
If exp IsNot Nothing Then
RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(exp.Member.Name))
End If
End Sub
End Class
The main benefit of doing this is refactoring. If I ever rename my property, the Lambda (and by extension NotifyPropertyChanged event) changes automatically.
这样做的主要好处是重构。如果我重命名我的属性，Lambda（以及扩展 NotifyPropertyChanged 事件）会自动更改。
Update (2015)
更新 (2015)
It may be worth mentioning that the new features in Visual Studio 2015 make this even easier. Below is the same code shown above, but using the new nameoffeature (Details of this, and of other new features can be found Here).
值得一提的是，Visual Studio 2015 中的新功能使这变得更加容易。下面是上面显示的相同代码，但使用了新nameof功能（可以在此处找到有关此和其他新功能的详细信息）。
C#
C＃
public class Test : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
string _Name;
public string Name
{
get { return _Name; }
set
{
_Name = value;
RaisePropertyChanged(nameof(Name));
}
}
private void RaisePropertyChanged(string property)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(property));
}
}
}
VB
VB
Public Class Test
Implements INotifyPropertyChanged
Public Event PropertyChanged(sender As Object, e As PropertyChangedEventArgs) Implements INotifyPropertyChanged.PropertyChanged
Private _Name As String
Public Property Name() As String
Get
Return _Name
End Get
Set(value As String)
_Name = value
RaisePropertyChanged(NameOf(Name))
End Set
End Property
Private Sub RaisePropertyChanged(propertyName As String)
RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(propertyName))
End Sub
End Class
You can even use nameofon the subscriber side, in order to determine if the property is the one you care about:
您甚至可以nameof在订阅者端使用，以确定该属性是否是您关心的：
private static void PropChanged(object sender, PropertyChangedEventArgs e)
{
if (e.PropertyName == nameof(Test.Name))
{
Console.WriteLine("The Property I care about changed");
}
}
回答by Stefan Vasiljevic
For someone who is still looking for an elegant solution, in the latest version of VB and C# you can use "nameof()".
对于仍在寻找优雅解决方案的人，在最新版本的 VB 和 C# 中，您可以使用“nameof()”。
C#:
C＃：
var propertyName = nameof(objAddress.AddressLine)
VB .NET:
VB.NET：
Dim propertyName = nameof(objAddress.AddressLine)
Note that if you do not have an instance of an object you can just use it's class name.
请注意，如果您没有对象的实例，则可以仅使用它的类名。
回答by laylarenee
This will show the current Method. You may want to replace the "get_" prefix of the property name.
这将显示当前方法。您可能想要替换属性名称的“get_”前缀。
Public Class People
Public Shared ReadOnly Property Address As String
Get
Return System.Reflection.MethodInfo.GetCurrentMethod().ToString()
End Get
End Property
End Class
' print it
System.Diagnostics.Debug.Print(People.Address)
回答by Lykeuhfox
I decided to go with the_lotus's response to my initial question which was to use a constant. If I find a more dynamic way to do this in the near future I'll try to post it. lotus, if you happen to see this an answer the question with your comment, i'll switch the answered status over to you.
我决定采用 the_lotus 对我最初使用常量的问题的回答。如果我在不久的将来找到一种更动态的方法来做到这一点，我会尝试发布它。莲花，如果您碰巧看到此问题并通过您的评论回答问题，我会将回答状态切换给您。
回答by Babblo
From MSDN
来自MSDN
Imports System
Imports System.Reflection
Class MyClass1
Private myProperty1 As Integer
' Declare MyProperty.
Public Property MyProperty() As Integer
Get
Return myProperty1
End Get
Set(ByVal Value As Integer)
myProperty1 = Value
End Set
End Property
End Class 'MyClass1
Public Class MyTypeClass
Public Shared Sub Main(ByVal args() As String)
Try
' Get Type Object corresponding to MyClass.
Dim myType As Type = GetType(MyClass1)
' Get PropertyInfo object by passing property name.
Dim myPropInfo As PropertyInfo = myType.GetProperty("MyProperty")
' Display Name propety to console.
Console.WriteLine("The {0} property exists in MyClass.", myPropInfo.Name)
Catch e As NullReferenceException
Console.WriteLine("The property does not exist in MyClass.", e.Message.ToString())
End Try
End Sub 'Main
End Class 'MyTypeClass
回答by Crab Apple
Using the System.Runtime.CompilerServices works wonders in this case, as of Net4.5. [See Caller Information] The optional CallerMemberName string can be used to identify what method/property called the log.
从 Net4.5 开始，在这种情况下使用 System.Runtime.CompilerServices 会产生奇迹。[查看调用者信息] 可选的 CallerMemberName 字符串可用于标识调用日志的方法/属性。
From MSDN
来自MSDN
Private Sub DoProcessing()
TraceMessage("Something happened.")
End Sub
Public Sub TraceMessage(message As String,
<System.Runtime.CompilerServices.CallerMemberName> Optional memberName As String = Nothing,
<System.Runtime.CompilerServices.CallerFilePath> Optional sourcefilePath As String = Nothing,
<System.Runtime.CompilerServices.CallerLineNumber()> Optional sourceLineNumber As Integer = 0)
System.Diagnostics.Trace.WriteLine("message: " & message)
System.Diagnostics.Trace.WriteLine("member name: " & memberName)
System.Diagnostics.Trace.WriteLine("source file path: " & sourcefilePath)
System.Diagnostics.Trace.WriteLine("source line number: " & sourceLineNumber)
End Sub
' Sample output:
' message: Something happened.
' member name: DoProcessing
' source file path: C:\Users\username\Documents\Visual Studio 2012\Projects\CallerInfoVB\CallerInfoVB\Form1.vb
' source line number: 15
Different implementation showing results from a Property Call
显示属性调用结果的不同实现
Class Foo
Public ReadOnly Property ThisPropertyObject As Object
Get
LogManager.Ping
Return Nothing
End Get
End Property
Sub New()
Dim this = ThisPropertyObject
End Sub
End Class
Public Module LogManager
Public Sub Ping(<CallerMemberName> Optional memberName As String = Nothing,
<CallerFilePath> Optional sourcefilePath As String = Nothing,
<CallerLineNumber> Optional sourceLineNumber As Integer = 0)
Trace.Writeline(String.Format("[{0}]|{1}|LN:{2}] <PING>",
Path.GetFileName(sourcefilePath),
memberName,
sourceLineNumber)
)
)
End Sub
End Module
'! Results from 'DebugView'
' [20692][LogTestFile.vb|ThisPropertyObject|LN:62] <PING>
