在C＃中合并两个对象

Question

我有一个具有各种属性的对象模型MyObject。有一次，我有两个这样的MyObject实例：实例A和实例B.如果实例B具有非空值，我想将实例A中的属性复制并替换为实例B的属性。

如果我只有1个具有3个属性的类，没问题，我可以轻松地对其进行硬编码（这是我开始做的）。但实际上我有12个不同的对象模型，每个模型有10个属性。

这样做的好方法是什么？

Answer 1

<强>更新 如果您需要经常调用此方法，请使用AutoMapper。 Automapper使用Reflection.Emit构建动态方法，并且比反射快得多。'

您可以使用反射复制属性的值：

public void CopyValues<T>(T target, T source)
{
    Type t = typeof(T);

    var properties = t.GetProperties().Where(prop => prop.CanRead && prop.CanWrite);

    foreach (var prop in properties)
    {
        var value = prop.GetValue(source, null);
        if (value != null)
             prop.SetValue(target, value, null);
    }
}

我已将其设为通用以确保类型安全。如果要包含私有属性，则应使用覆盖Type.GetProperties()，指定绑定标记。

Answer 2

我已经尝试了凯尔芬利的Merge Two Objects into an Anonymous Type，它的工作非常完美。

使用TypeMerger合并就像

一样简单

var obj1 = new {foo = "foo"};

var obj2 = new {bar = "bar"};

var mergedObject = TypeMerger.MergeTypes(obj1 , obj2 );

你得到了合并的对象，除此之外，还有一项规定可以忽略特定的属性。你也可以对MVC3使用相同的东西。

Answer 3

你可以使用反射来做到这一点，但正如有人说的那样，它会有性能损失。

由于您正在使用预期的类设计，因此可以使用类似的扩展方法实现相同的目标：

public static class MyClassExtensions
{
    public static void Merge(this MyClass instanceA, MyClass instanceB)
    {
        if(instanceA != null && instanceB != null)
        {
             if(instanceB.Prop1 != null) 
             {
                 instanceA.Prop1 = instanceB.Prop1;
             }


             if(instanceB.PropN != null) 
             {
                 instanceA.PropN = instanceB.PropN;
             }
    }
}

以后，代码中的某处：

someInstanceOfMyClass.Merge(someOtherInstanceOfMyClass);

在一天结束时，您已将此操作集中在扩展方法中，如果添加或删除类的属性，则只需修改扩展方法的实现，即可完成所有操作。

Answer 4

这与@Bas答案相同，但对于合并2对象列表

public class Copycontents
{
    public static void Work<T>(IList<T> targetList, IList<T> sourceList, Func<T, int> selector)
    {
        var matchingPrimaryKey = targetList.Select(x => selector(x)).ToList();

        foreach (var thismatchingPrimaryKey in matchingPrimaryKey)
        {
            CopyValues<T>(targetList.Single(x => selector(x) == thismatchingPrimaryKey),
                sourceList.Single(x => selector(x) == thismatchingPrimaryKey));
        }
    }

    private static void CopyValues<T>(T target, T source)
    {
        Type t = typeof(T);

        var properties = t.GetProperties().Where(prop => prop.CanRead && prop.CanWrite);

        foreach (var prop in properties)
        {
            var value = prop.GetValue(source, null);
            if (value != null)
                prop.SetValue(target, value, null);
        }
    }
}

Answer 5

我为此目的编写了自己的课程：ObjectMerger。

基本上它使用反射（因此可能很慢）。它还包含更多功能，例如解析循环引用的对象并合并它们。我的ObjectMerger还包含处理更复杂类的机制，如string1 = (1 1 1 4 10) var total = parseFloat(0); for(var j=0; j<string1.length; j++) { total += parseFloat(string1.charAt(j)); } 或Delegate。这些将被完全复制，类中的其他对象以递归方式合并。

语法如下：

MemberInfo

我很遗憾地说它不是按原样使用，因为由于我公司的限制，目前存储库中缺少一些外部库，但它们很容易被重写。我希望将来可以添加它们。

Answer 6

您可以使用以下软件包：XASoft

使用foo.Merger（bar）方法 将2个对象组合成一个动态对象

just like this

Collecting mysqlclient
  Using cached https://files.pythonhosted.org/packages/f4/f1/3bb6f64ca7a429729413e6556b7ba5976df06019a5245a43d36032f1061e/mysqlclient-1.4.2.post1.tar.gz
Building wheels for collected packages: mysqlclient
  Building wheel for mysqlclient (setup.py) ... error
  Complete output from command c:\users\adity\desktop\dev\blog\env\scripts\python.exe -u -c "import setuptools, tokenize;__file__='C:\\Users\\adity\\AppData\\Local\\Temp\\pip-install-wxr9hw0f\\mysqlclient\\setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" bdist_wheel -d C:\Users\adity\AppData\Local\Temp\pip-wheel-zjrz983m --python-tag cp37:
  running bdist_wheel
  running build
  running build_py
  creating build
  creating build\lib.win32-3.7
  creating build\lib.win32-3.7\MySQLdb
  copying MySQLdb\__init__.py -> build\lib.win32-3.7\MySQLdb
  copying MySQLdb\_exceptions.py -> build\lib.win32-3.7\MySQLdb
  copying MySQLdb\compat.py -> build\lib.win32-3.7\MySQLdb
  copying MySQLdb\connections.py -> build\lib.win32-3.7\MySQLdb
  copying MySQLdb\converters.py -> build\lib.win32-3.7\MySQLdb
  copying MySQLdb\cursors.py -> build\lib.win32-3.7\MySQLdb
  copying MySQLdb\release.py -> build\lib.win32-3.7\MySQLdb
  copying MySQLdb\times.py -> build\lib.win32-3.7\MySQLdb
  creating build\lib.win32-3.7\MySQLdb\constants
  copying MySQLdb\constants\__init__.py -> build\lib.win32-3.7\MySQLdb\constants
  copying MySQLdb\constants\CLIENT.py -> build\lib.win32-3.7\MySQLdb\constants
  copying MySQLdb\constants\CR.py -> build\lib.win32-3.7\MySQLdb\constants
  copying MySQLdb\constants\ER.py -> build\lib.win32-3.7\MySQLdb\constants
  copying MySQLdb\constants\FIELD_TYPE.py -> build\lib.win32-3.7\MySQLdb\constants
  copying MySQLdb\constants\FLAG.py -> build\lib.win32-3.7\MySQLdb\constants
  running build_ext
  building 'MySQLdb._mysql' extension
  creating build\temp.win32-3.7
  creating build\temp.win32-3.7\Release
  creating build\temp.win32-3.7\Release\MySQLdb
  C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\BIN\cl.exe /c /nologo /Ox /W3 /GL /DNDEBUG /MD -Dversion_info=(1,4,2,'post',1) -D__version__=1.4.2.post1 "-IC:\Program Files (x86)\MySQL\MySQL Connector C 6.1\include\mariadb" -Ic:\users\adity\appdata\local\programs\python\python37-32\include -Ic:\users\adity\appdata\local\programs\python\python37-32\include "-IC:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE" "-IC:\Program Files (x86)\Windows Kits\10\include\10.0.10240.0\ucrt" "-IC:\Program Files (x86)\Windows Kits\8.1\include\shared" "-IC:\Program Files (x86)\Windows Kits\8.1\include\um" "-IC:\Program Files (x86)\Windows Kits\8.1\include\winrt" /TcMySQLdb/_mysql.c /Fobuild\temp.win32-3.7\Release\MySQLdb/_mysql.obj /Zl /D_CRT_SECURE_NO_WARNINGS
  _mysql.c
  MySQLdb/_mysql.c(29): fatal error C1083: Cannot open include file: 'mysql.h': No such file or directory
  error: command 'C:\\Program Files (x86)\\Microsoft Visual Studio 14.0\\VC\\BIN\\cl.exe' failed with exit status 2

  ----------------------------------------
  Failed building wheel for mysqlclient
  Running setup.py clean for mysqlclient
Failed to build mysqlclient
Installing collected packages: mysqlclient
  Running setup.py install for mysqlclient ... error
    Complete output from command c:\users\adity\desktop\dev\blog\env\scripts\python.exe -u -c "import setuptools, tokenize;__file__='C:\\Users\\adity\\AppData\\Local\\Temp\\pip-install-wxr9hw0f\\mysqlclient\\setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" install --record C:\Users\adity\AppData\Local\Temp\pip-record-wtvbzmsb\install-record.txt --single-version-externally-managed --compile --install-headers c:\users\adity\desktop\dev\blog\env\include\site\python3.7\mysqlclient:
    running install
    running build
    running build_py
    creating build
    creating build\lib.win32-3.7
    creating build\lib.win32-3.7\MySQLdb
    copying MySQLdb\__init__.py -> build\lib.win32-3.7\MySQLdb
    copying MySQLdb\_exceptions.py -> build\lib.win32-3.7\MySQLdb
    copying MySQLdb\compat.py -> build\lib.win32-3.7\MySQLdb
    copying MySQLdb\connections.py -> build\lib.win32-3.7\MySQLdb
    copying MySQLdb\converters.py -> build\lib.win32-3.7\MySQLdb
    copying MySQLdb\cursors.py -> build\lib.win32-3.7\MySQLdb
    copying MySQLdb\release.py -> build\lib.win32-3.7\MySQLdb
    copying MySQLdb\times.py -> build\lib.win32-3.7\MySQLdb
    creating build\lib.win32-3.7\MySQLdb\constants
    copying MySQLdb\constants\__init__.py -> build\lib.win32-3.7\MySQLdb\constants
    copying MySQLdb\constants\CLIENT.py -> build\lib.win32-3.7\MySQLdb\constants
    copying MySQLdb\constants\CR.py -> build\lib.win32-3.7\MySQLdb\constants
    copying MySQLdb\constants\ER.py -> build\lib.win32-3.7\MySQLdb\constants
    copying MySQLdb\constants\FIELD_TYPE.py -> build\lib.win32-3.7\MySQLdb\constants
    copying MySQLdb\constants\FLAG.py -> build\lib.win32-3.7\MySQLdb\constants
    running build_ext
    building 'MySQLdb._mysql' extension
    creating build\temp.win32-3.7
    creating build\temp.win32-3.7\Release
    creating build\temp.win32-3.7\Release\MySQLdb
    C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\BIN\cl.exe /c /nologo /Ox /W3 /GL /DNDEBUG /MD -Dversion_info=(1,4,2,'post',1) -D__version__=1.4.2.post1 "-IC:\Program Files (x86)\MySQL\MySQL Connector C 6.1\include\mariadb" -Ic:\users\adity\appdata\local\programs\python\python37-32\include -Ic:\users\adity\appdata\local\programs\python\python37-32\include "-IC:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE" "-IC:\Program Files (x86)\Windows Kits\10\include\10.0.10240.0\ucrt" "-IC:\Program Files (x86)\Windows Kits\8.1\include\shared" "-IC:\Program Files (x86)\Windows Kits\8.1\include\um" "-IC:\Program Files (x86)\Windows Kits\8.1\include\winrt" /TcMySQLdb/_mysql.c /Fobuild\temp.win32-3.7\Release\MySQLdb/_mysql.obj /Zl /D_CRT_SECURE_NO_WARNINGS
    _mysql.c
    MySQLdb/_mysql.c(29): fatal error C1083: Cannot open include file: 'mysql.h': No such file or directory
    error: command 'C:\\Program Files (x86)\\Microsoft Visual Studio 14.0\\VC\\BIN\\cl.exe' failed with exit status 2

    ----------------------------------------
Command "c:\users\adity\desktop\dev\blog\env\scripts\python.exe -u -c "import setuptools, tokenize;__file__='C:\\Users\\adity\\AppData\\Local\\Temp\\pip-install-wxr9hw0f\\mysqlclient\\setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" install --record C:\Users\adity\AppData\Local\Temp\pip-record-wtvbzmsb\install-record.txt --single-version-externally-managed --compile --install-headers c:\users\adity\desktop\dev\blog\env\include\site\python3.7\mysqlclient" failed with error code 1 in C:\Users\adity\AppData\Local\Temp\pip-install-wxr9hw0f\mysqlclient\

even if object list works fine too!

var objA = new { a = 1, b = 2, c = 3 };
var newObj = objA.Merger(new { a = "Hey", d = 4, e = 5 });
newObj.e = "There";
newObj.f = 6;
Console.WriteLine(JsonConvert.SerializeObject(newObj));

糟糕，看起来像JavaScript语言...

btw,source code click here