VB.NET:通过反射实例化嵌套属性

Question

我想通过反射来设置属性的值。在这个线程中，他们提出了一个解决方案。但是解决方案的问题在于它没有实例化属性。但我想在必要时检查并实例化属性。我的 DTO 是：

Public Class root
Public Property Printing() As rootPrinting
End Class
Public Class rootPrinting
Public Property Printer() As String
Public Property PrinterBatch() As String
End Class

现在为了设置属性，我定义了以下函数：

Public Sub SetProperty(ByVal target As Object, ByVal compoundProperty As String, ByVal value As Object)
Dim properties As String() = compoundProperty.Split("."c)
For i As Integer = 0 To properties.Length - 1 - 1
Dim propertyToGet As PropertyInfo = target.[GetType]().GetProperty(properties(i))
target = propertyToGet.GetValue(target, Nothing)
if IsNothing(target) then
if propertyToGet.PropertyType.IsClass then
target = Activator.CreateInstance(propertyToGet.PropertyType)
End If
End If
Next
Dim propertyToSet As PropertyInfo = target.[GetType]().GetProperty(properties.Last())
propertyToSet.SetValue(target, value, Nothing)
End Sub

然后我这样称呼它：

Dim configObject as New root
SetProperty(configObject , "Printing.Printer","skjfkd")

如果在调用SetProperty(configObject,...)之前我实例化configObject.Printing那么它将正常工作：

Dim configObject as New root
configObject.Printing = new rootPrinting()
SetProperty(configObject , "Printing.Printer","skjfkd") 

否则调用SetProperty(...)后，configObject.Printing将被Nothing.
似乎在调用Activator.CreateInstance(propertyToGet.PropertyType)时，对原始对象的引用丢失了。当函数中的对象真正初始化时，主对象仍然是Nothing。如何正确实例化类属性？

Answer 1

这个问题/答案对我非常有帮助(感谢Code Pope！(，我需要在C#中使用相同的代码：

public void SetProperty(object target, string compoundProperty, object value)
{
var properties = compoundProperty.Split('.');
for (int i=0; i < (properties.Length - 1); i++)
{
var propertyToGet = target.GetType().GetProperty(properties[i]);
var property_value = propertyToGet.GetValue(target, null);
if (property_value == null)
{
if (propertyToGet.PropertyType.IsClass)
{
property_value = Activator.CreateInstance(propertyToGet.PropertyType);
propertyToGet.SetValue(target, property_value);
}
}
target = property_value;
}
var propertyToSet = target.GetType().GetProperty(properties.Last());
propertyToSet.SetValue(target, value);
}

Answer 2

好的。问题解决了。要解决此问题，必须按如下方式修改代码：

Public Sub SetProperty(ByVal target As Object, ByVal compoundProperty As String, ByVal value As Object)
Dim properties As String() = compoundProperty.Split("."c)
For i As Integer = 0 To properties.Length - 1 - 1
Dim propertyToGet As PropertyInfo = target.GetType().GetProperty(properties(i))
Dim property_value = propertyToGet.GetValue(target, Nothing)
If IsNothing(property_value) Then
If propertyToGet.PropertyType.IsClass Then
property_value = Activator.CreateInstance(propertyToGet.PropertyType)
propertyToGet.SetValue(target, property_value)
End If
End If
target = property_value
Next
Dim propertyToSet As PropertyInfo = target.GetType().GetProperty(properties.Last())
propertyToSet.SetValue(target, value)
End Sub