c# - 如何遍历类字段并设置属性

c# - How to iterate through classes fields and set properties

提问by Petras

I am not sure if this is possible but I want to iterate through a class and set a field member property without referring to the field object explicitly:

我不确定这是否可行，但我想遍历一个类并设置一个字段成员属性而不显式引用字段对象：

public class Employee
{
  public Person _person = new Person();

  public void DynamicallySetPersonProperty()
  {
    MemberInfo[] members = this.GetType().GetMembers();

    foreach (MemberInfo member in members.Where(a => a.Name == "_person"))
    //get the _person field
    {

      Type type = member.GetType();
      PropertyInfo prop = type.GetProperty("Name"); //good, this works, now to set a value for it

      //this line does not work - the error is "property set method not found"
      prop.SetValue(member, "new name", null);
    }
  }
}


public class Person
{
  public string Name { get; set; }
}

In the answer that I marked as the answer you need to add:

在我标记为答案的答案中，您需要添加：

  public static bool IsNullOrEmpty(this string source)
  {
    return (source == null || source.Length > 0) ? true : false;
  }

采纳答案by Konstantin Tarkus

public class Person
{
    public string Name { get; set; }
}

public class Employee
{
    public Person person = new Person();

    public void DynamicallySetPersonProperty()
    {
        var p = GetType().GetField("person").GetValue(this);
        p.GetType().GetProperty("Name").SetValue(p, "new name", null);
    }
}

回答by Chris Ballance

Have a look on this CodeProject article related to what you are trying to do

看看这篇与你正在尝试做的事情相关的 CodeProject 文章

http://www.codeproject.com/KB/cs/fast_dynamic_properties.aspx

http://www.codeproject.com/KB/cs/fast_dynamic_properties.aspx

回答by David M

You are trying to set the Name property of your Employee class's _person field. It doesn't have one. Try this:

您正在尝试设置 Employee 类的 _person 字段的 Name 属性。它没有。尝试这个：

prop.SetValue(((FieldInfo)member).GetValue(this), "new name", null)

Not sure if you need to cast the first argument like this:

不确定是否需要像这样转换第一个参数：

prop.SetValue((Person)((FieldInfo)member).GetValue(this), "new name", null)

This then applies it to the value of the _person field instead.

然后将其应用于 _person 字段的值。

回答by Daniel Brückner

You a trying to perform SetValue()on the property Nameof the variable memberthat is a MemberInfo object and this proeprty is read only.

您尝试对作为 MemberInfo 对象的变量SetValue()的属性执行操作，并且此属性是只读的。Namemember

Note you do not need to iterate over all memebers and you do not need to get the field _personwith reflection as it is defined in the same class as the method DynamicallySetPersonProperty().

请注意，您不需要遍历所有成员，也不需要_person使用反射获取字段，因为它与方法在同一类中定义DynamicallySetPersonProperty()。

So the code shoul read like this.

所以代码应该是这样的。

PropertyInfo property = this._person.GetType().GetProperty("Name");

property.SetValue(this._person, "new name", null);

The first line will fail if _personis null. So you can use reflectiopn to get the type of the field.

如果_person为空，第一行将失败。所以你可以使用reflectionpn来获取字段的类型。

FieldInfo field = this.GetType().GetField("_person", BindingFlags.Public);

PropertyInfo property = field.FieldType.GetProperty("Name");

But now accessing this property will still fail if _personis null.

但是现在如果_person为空，访问这个属性仍然会失败。

property.Setvalue(field.GetValue(this), "new name", null);

回答by plinth

Here's a complete working example:

这是一个完整的工作示例：

public class Person
{
    public string Name { get; set; }
}

class Program
{
    static void PropertySet(object p, string propName, object value)
    {
        Type t = p.GetType();
        PropertyInfo info = t.GetProperty(propName);
        if (info == null)
            return;
        if (!info.CanWrite)
            return;
        info.SetValue(p, value, null);
    }

    static void PropertySetLooping(object p, string propName, object value)
    {
        Type t = p.GetType();
        foreach (PropertyInfo info in t.GetProperties())
        {
            if (info.Name == propName && info.CanWrite)
            {
                info.SetValue(p, value, null);
            }
        }
    }

    static void Main(string[] args)
    {
        Person p = new Person();

        PropertySet(p, "Name", "Michael Ellis");
        Console.WriteLine(p.Name);
        PropertySetLooping(p, "Name", "Nigel Mellish");
        Console.WriteLine(p.Name);
    }
}

EDIT: added a looping variant so you could see how to loop through property info objects.

编辑：添加了一个循环变体，以便您可以了解如何循环访问属性信息对象。

回答by Paleta

With the following Extension methods that I have created, you can set or get any property value even if they are nested

使用我创建的以下扩展方法，您可以设置或获取任何属性值，即使它们是嵌套的

GetPropertyValue(customObject, "Property.Nested.Child.Name");

GetPropertyValue(customObject, "Property.Nested.Child.Name");

or set

或设置

SetPropertyValue(customObject, "Property.Nested.Child.Name", "my custom name");

SetPropertyValue(customObject, "Property.Nested.Child.Name", "我的自定义名称");

        private class TargetProperty
    {
        public object Target { get; set; }
        public PropertyInfo Property { get; set; }

        public bool IsValid { get { return Target != null && Property != null; } }
    }

    private static TargetProperty GetTargetProperty(object source, string propertyName)
    {
        if (!propertyName.Contains("."))
            return new TargetProperty { Target = source, Property = source.GetType().GetProperty(propertyName) };

        string[] propertyPath = propertyName.Split('.');

        var targetProperty = new TargetProperty();

        targetProperty.Target = source;
        targetProperty.Property = source.GetType().GetProperty(propertyPath[0]);

        for (int propertyIndex = 1; propertyIndex < propertyPath.Length; propertyIndex++)
        {
            propertyName = propertyPath[propertyIndex];
            if (!string.IsNullOrEmpty(propertyName))
            {
                targetProperty.Target = targetProperty.Property.GetValue(targetProperty.Target, null);
                targetProperty.Property = targetProperty.Target.GetType().GetProperty(propertyName);
            }
        }

        return targetProperty;
    }


    public static bool HasProperty(this object source, string propertyName)
    {
        return GetTargetProperty(source, propertyName).Property != null;
    }

    public static object GetPropertyValue(this object source, string propertyName)
    {
        var targetProperty = GetTargetProperty(source, propertyName);
        if (targetProperty.IsValid)
        {
            return targetProperty.Property.GetValue(targetProperty.Target, null);
        }
        return null;
    }

    public static void SetPropertyValue(this object source, string propertyName, object value)
    {
        var targetProperty = GetTargetProperty(source, propertyName);
        if(targetProperty.IsValid)
        {
            targetProperty.Property.SetValue(targetProperty.Target, value, null);
        }
    }

And here are a couple of tests for it

这里有几个测试

    [TestFixture]
public class ObjectExtensionsTest
{

    private class MockClass
    {
        public MockClass()
        {
            Nested = new NestedMockClass();
        }

        public string Id { get; set; }
        public string Name { get; set; }

        public string GetOnly { get { return "MockClass"; } }
        public string SetOnly { set { } }

        public NestedMockClass Nested { get; set; }
    }

    private class NestedMockClass
    {
        public string NestedId { get; set; }
        public string NestedName { get; set; }

        public string NestedGetOnly { get { return "NestedMockClass"; } }
        public string NestedSetOnly { set { } }
    }

    [Test]
    public void TestShouldFindProperty()
    {
        MockClass mockObject = new MockClass();

        Assert.IsTrue(mockObject.HasProperty("Id"));
        Assert.IsTrue(mockObject.HasProperty("Name"));
        Assert.IsTrue(mockObject.HasProperty("GetOnly"));
        Assert.IsTrue(mockObject.HasProperty("SetOnly"));
        Assert.IsTrue(mockObject.HasProperty("Nested"));
        Assert.IsTrue(mockObject.HasProperty("Nested.NestedId"));
        Assert.IsTrue(mockObject.HasProperty("Nested.NestedName"));
        Assert.IsTrue(mockObject.HasProperty("Nested.NestedGetOnly"));
        Assert.IsTrue(mockObject.HasProperty("Nested.NestedSetOnly"));
    }

    [Test]
    public void TestShouldGetPropertyValue()
    {
        MockClass mockObject = new MockClass();

        mockObject.Id = "1";
        mockObject.Name = "Name";
        mockObject.Nested.NestedId = "NestedId";
        mockObject.Nested.NestedName = "NestedName";

        Assert.AreEqual(mockObject.Id, mockObject.GetPropertyValue("Id"));
        Assert.AreEqual(mockObject.Name, mockObject.GetPropertyValue("Name"));
        Assert.AreEqual(mockObject.GetOnly, mockObject.GetPropertyValue("GetOnly"));
        Assert.AreEqual(mockObject.Nested.NestedId, mockObject.GetPropertyValue("Nested.NestedId"));
        Assert.AreEqual(mockObject.Nested.NestedName, mockObject.GetPropertyValue("Nested.NestedName"));

    }

    [Test]
    public void TestShouldSetPropertyValue()
    {
        MockClass mockObject = new MockClass();

        mockObject.SetPropertyValue("Id", "1");
        mockObject.SetPropertyValue("Name", "Name");
        mockObject.SetPropertyValue("Nested.NestedId", "NestedId");
        mockObject.SetPropertyValue("Nested.NestedName", "NestedName");

        Assert.AreEqual(mockObject.Id, "1");
        Assert.AreEqual(mockObject.Name, "Name");
        Assert.AreEqual(mockObject.Nested.NestedId, "NestedId");
        Assert.AreEqual(mockObject.Nested.NestedName, "NestedName");

    }
}

Hope you find it useful.

希望你觉得它有用。

回答by Paleta

try this:

尝试这个：

public static void ApplyPropertyChanges(this object objDest, object objToCopyFrom)
    {
        if (objDest == null)
            throw new ArgumentNullException();
        if (objToCopyFrom == null)
            throw new ArgumentNullException("objToCopyFrom");
        if (objDest.GetType() != objToCopyFrom.GetType())
            throw new Exception("Invalid type. Required: \"" + objDest.GetType().ToString() + "\"");

        foreach (System.Reflection.PropertyInfo piOrig in objDest.GetType().GetProperties())
        {
            object editedVal = objToCopyFrom.GetType().GetProperty(piOrig.Name).GetValue(objToCopyFrom, null);

            piOrig.SetValue(objDest,
            editedVal,
            null);
        }
    }

usage example:

用法示例：

    public ActionResult Edit(Team editedTeamData)
    {
        if (!ModelState.IsValid)
            return View();

        Team origTeam = (from t in _db.Teams
                         where t.TeamID == editedTeamData.TeamID
                         select t).FirstOrDefault();

        origTeam.ApplyPropertyChanges(editedTeamData);
        _db.SubmitChanges();

        return RedirectToAction("Index");

    }