C＃使用Reflection来复制基类属性

Question

我想使用Reflection将所有属性从MyObject更新到另一个属性。我遇到的问题是特定对象是从基类继承而且那些基类属性值没有更新。

以下代码复制顶级属性值。

public void Update(MyObject o)
{
    MyObject copyObject = ...

    FieldInfo[] myObjectFields = o.GetType().GetFields(
    BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance);

    foreach (FieldInfo fi in myObjectFields)
    {
        fi.SetValue(copyObject, fi.GetValue(o));
    }
}

我正在寻找是否有更多BindingFlags属性可以用来帮助但无济于事。

Answer 1

试试这个：

public void Update(MyObject o)
{
    MyObject copyObject = ...
    Type type = o.GetType();
    while (type != null)
    {
        UpdateForType(type, o, copyObject);
        type = type.BaseType;
    }
}

private static void UpdateForType(Type type, MyObject source, MyObject destination)
{
    FieldInfo[] myObjectFields = type.GetFields(
        BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance);

    foreach (FieldInfo fi in myObjectFields)
    {
        fi.SetValue(destination, fi.GetValue(source));
    }
}

Answer 2

我将此作为一种扩展方法编写，也适用于不同类型。我的问题是我有一些绑定到asp mvc表单的模型，以及映射到数据库的其他实体。理想情况下，我只有1个类，但实体是分阶段构建的，而asp mvc模型想要一次验证整个模型。

以下是代码：

public static class ObjectExt
{
    public static T1 CopyFrom<T1, T2>(this T1 obj, T2 otherObject)
        where T1: class
        where T2: class
    {
        PropertyInfo[] srcFields = otherObject.GetType().GetProperties(
            BindingFlags.Instance | BindingFlags.Public | BindingFlags.GetProperty);

        PropertyInfo[] destFields = obj.GetType().GetProperties(
            BindingFlags.Instance | BindingFlags.Public | BindingFlags.SetProperty);

        foreach (var property in srcFields) {
            var dest = destFields.FirstOrDefault(x => x.Name == property.Name);
            if (dest != null && dest.CanWrite)
                dest.SetValue(obj, property.GetValue(otherObject, null), null);
        }

        return obj;
    }
}

Answer 3

嗯。我认为GetFields会让你的成员从链中一路走来，如果没有想要继承成员，你必须明确指定BindingFlags.DeclaredOnly。所以我做了一个快速测试，我是对的。

然后我注意到了一些事情：

  

我想更新所有属性   从MyObject到另一个使用   反射。我要来的问题   进入就是特定的对象   继承自基类和那些   基类属性值不是   更新。

     

以下代码复制到顶层   财产价值。

public void Update(MyObject o) {
  MyObject copyObject = ...

  FieldInfo[] myObjectFields = o.GetType().GetFields(
  BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance);

这将只获得字段（包括此类上的私有字段），但不包含属性。所以如果你有这个层次结构（请原谅名字！）：

class L0
{
    public int f0;
    private int _p0;
    public int p0
    {
        get { return _p0; }
        set { _p0 = value; }
    }
}

class L1 : L0
{
    public int f1;
    private int _p1;
    public int p1
    {
        get { return _p1; }
        set { _p1 = value; }
    }
}

class L2 : L1
{
    public int f2;
    private int _p2;
    public int p2
    {
        get { return _p2; }
        set { _p2 = value; }
    }
}

然后使用您指定的.GetFields L2上的BindingFlags将获得f0，f1，f2和{{1} }，但不是_p2或p0（属性，而不是字段）或p1或_p0（它们是基类的私有，因此是{{1}类型的对象{1}} 没有这些字段。

如果您想复制属性，请尝试执行您正在执行的操作，但请改用_p1。

Answer 4

这不考虑带参数的属性，也不考虑可能无法访问的私有get / set访问器，也不考虑只读枚举，所以这是一个扩展的解决方案？

我尝试转换为C＃，但通常的来源没有这样做，我没有时间自己转换它。

''' <summary>
''' Import the properties that match by name in the source to the target.</summary>
''' <param name="target">Object to import the properties into.</param>
''' <param name="source">Object to import the properties from.</param>
''' <returns>
''' True, if the import can without exception; otherwise, False.</returns>
<System.Runtime.CompilerServices.Extension()>
Public Function Import(target As Object, source As Object) As Boolean
    Dim targetProperties As IEnumerable(Of Tuple(Of Reflection.PropertyInfo, Reflection.MethodInfo)) =
        (From aPropertyInfo In source.GetType().GetProperties(Reflection.BindingFlags.Public Or Reflection.BindingFlags.NonPublic Or Reflection.BindingFlags.Instance)
         Let propertyAccessors = aPropertyInfo.GetAccessors(True)
         Let propertyMethods = aPropertyInfo.PropertyType.GetMethods()
         Let addMethod = (From aMethodInfo In propertyMethods
                          Where aMethodInfo.Name = "Add" AndAlso aMethodInfo.GetParameters().Length = 1
                          Select aMethodInfo).FirstOrDefault()
         Where aPropertyInfo.CanRead AndAlso aPropertyInfo.GetIndexParameters().Length = 0 _
          AndAlso (aPropertyInfo.CanWrite OrElse addMethod IsNot Nothing) _
          AndAlso (From aMethodInfo In propertyAccessors
                   Where aMethodInfo.IsPrivate _
                    OrElse (aMethodInfo.Name.StartsWith("get_") OrElse aMethodInfo.Name.StartsWith("set_"))).FirstOrDefault() IsNot Nothing
         Select New Tuple(Of Reflection.PropertyInfo, Reflection.MethodInfo)(aPropertyInfo, addMethod))
    ' No properties to import into.
    If targetProperties.Count() = 0 Then Return True

    Dim sourceProperties As IEnumerable(Of Tuple(Of Reflection.PropertyInfo, Reflection.MethodInfo)) =
        (From aPropertyInfo In source.GetType().GetProperties(Reflection.BindingFlags.Public Or Reflection.BindingFlags.NonPublic Or Reflection.BindingFlags.Instance)
         Let propertyAccessors = aPropertyInfo.GetAccessors(True)
         Let propertyMethods = aPropertyInfo.PropertyType.GetMethods()
         Let addMethod = (From aMethodInfo In propertyMethods
                          Where aMethodInfo.Name = "Add" AndAlso aMethodInfo.GetParameters().Length = 1
                          Select aMethodInfo).FirstOrDefault()
         Where aPropertyInfo.CanRead AndAlso aPropertyInfo.GetIndexParameters().Length = 0 _
          AndAlso (aPropertyInfo.CanWrite OrElse addMethod IsNot Nothing) _
          AndAlso (From aMethodInfo In propertyAccessors
                   Where aMethodInfo.IsPrivate _
                    OrElse (aMethodInfo.Name.StartsWith("get_") OrElse aMethodInfo.Name.StartsWith("set_"))).FirstOrDefault() IsNot Nothing
         Select New Tuple(Of Reflection.PropertyInfo, Reflection.MethodInfo)(aPropertyInfo, addMethod))
    ' No properties to import.
    If sourceProperties.Count() = 0 Then Return True

    Try
        Dim currentPropertyInfo As Tuple(Of Reflection.PropertyInfo, Reflection.MethodInfo)
        Dim matchingPropertyInfo As Tuple(Of Reflection.PropertyInfo, Reflection.MethodInfo)

        ' Copy the properties from the source to the target, that match by name.
        For Each currentPropertyInfo In sourceProperties
            matchingPropertyInfo = (From aPropertyInfo In targetProperties
                                    Where aPropertyInfo.Item1.Name = currentPropertyInfo.Item1.Name).FirstOrDefault()
            ' If a property matches in the target, then copy the value from the source to the target.
            If matchingPropertyInfo IsNot Nothing Then
                If matchingPropertyInfo.Item1.CanWrite Then
                    matchingPropertyInfo.Item1.SetValue(target, matchingPropertyInfo.Item1.GetValue(source, Nothing), Nothing)
                ElseIf matchingPropertyInfo.Item2 IsNot Nothing Then
                    Dim isEnumerable As IEnumerable = TryCast(currentPropertyInfo.Item1.GetValue(source, Nothing), IEnumerable)
                    If isEnumerable Is Nothing Then Continue For
                    ' Invoke the Add method for each object in this property collection.
                    For Each currentObject As Object In isEnumerable
                        matchingPropertyInfo.Item2.Invoke(matchingPropertyInfo.Item1.GetValue(target, Nothing), New Object() {currentObject})
                    Next
                End If
            End If
        Next
    Catch ex As Exception
        Return False
    End Try

    Return True
End Function

Answer 5

Bogdan Litescu的解决方案效果很好，但我也会检查你是否可以写信给他们。

foreach (var property in srcFields) {
        var dest = destFields.FirstOrDefault(x => x.Name == property.Name);
        if (dest != null)
            if (dest.CanWrite)
                dest.SetValue(obj, property.GetValue(otherObject, null), null);
    }

Answer 6

我有一个从基础对象派生的对象，并为某些情况添加了额外的属性。但是想在派生对象的新实例上设置所有基础对象属性。即使以后向基础对象添加更多属性，我也不必担心添加硬编码行来设置派生对象中的基础属性。

感谢maciejkow，我提出了以下建议：

// base object
public class BaseObject
{
    public int ID { get; set; } = 0;
    public string SomeText { get; set; } = "";
    public DateTime? CreatedDateTime { get; set; } = DateTime.Now;
    public string AnotherString { get; set; } = "";
    public bool aBoolean { get; set; } = false;
    public int integerForSomething { get; set; } = 0;
}

// derived object
public class CustomObject : BaseObject
{
    public string ANewProperty { get; set; } = "";
    public bool ExtraBooleanField { get; set; } = false;

    //Set base object properties in the constructor
    public CustomObject(BaseObject source)
    {
        var properties = source.GetType().GetFields(System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Instance);

        foreach(var fi in properties)
        {
            fi.SetValue(this, fi.GetValue(source));
        }
    }
}

可以像这样简单地使用：

public CustomObject CreateNewCustomObject(BaseObject obj, string ANewProp, bool ExtraBool)
{
    return new CustomObject(obj)
    {
        ANewProperty = ANewProp,
        ExtraBooleanField = ExtraBool
    };
}

我有其他想法：

• 是否将仅强制转换对象工作？ (CustomObject)baseObject

  （我测试了投射并获得了System.InvalidCastException: 'Unable to cast object of type 'BaseObject' to type 'CustomObject'.'）

• 序列化为JSON字符串并反序列化为CustomObject？

  （我测试了序列化/反序列化-运作起来很吸引人，但是序列化/反序列化存在明显的滞后性）

因此在我的测试案例中，使用反射在派生对象的构造函数中设置属性是即时的。我确信JSON Serialize / Deserialize也会在任何情况下使用反射，但是要进行两次，而在具有反射的构造函数中进行转换仅发生一次。