使用反射从类列表中的属性中获取值 [英] Using reflection to get values from properties from a list of a class

问题描述

我正在尝试从属于主要对象的列表中的对象获取值.

I am trying to get the values from objects inside a list which is part of a main object.

我有一个包含各种属性的主对象，这些属性可以是集合.

I have the main object which contains various properties which can be collections.

现在我想弄清楚如何访问包含在对象中的通用列表.

Right now I am trying to figure out how to access a generic list which is contained in the object.

///<summary>
///Code for the inner class
///</summary>
public class TheClass
{
    public TheClass();

    string TheValue { get; set; }
} //Note this class is used for serialization so it won't compile as-is

///<summary>
///Code for the main class
///</summary>
public class MainClass
{
    public MainClass();

    public List<TheClass> TheList { get; set; }
    public string SomeOtherProperty { get; set; }
    public Class SomeOtherClass { get; set }
}


public List<MainClass> CompareTheValue(List<object> MyObjects, string ValueToCompare)
{ 
    //I have the object deserialised as a list
    var ObjectsToReturn = new List<MainClass>();
    foreach(var mObject in MyObjects)
    {

        //Gets the properties
        PropertyInfo piTheList = mObject.GetType().GetProperty("TheList");

        object oTheList = piTheList.GetValue(MyObject, null);


        //Now that I have the list object I extract the inner class 
        //and get the value of the property I want
        PropertyInfo piTheValue = oTheList.PropertyType
                                          .GetGenericArguments()[0]
                                          .GetProperty("TheValue");

        //get the TheValue out of the TheList and compare it for equality with
        //ValueToCompare
        //if it matches then add to a list to be returned

        //Eventually I will write a Linq query to go through the list to do the comparison.
        ObjectsToReturn.Add(objectsToReturn);

    }
return ObjectsToReturn;
}

我尝试在 MyObject 中使用 SetValue()，但它出错了(释义):

I've tried to use a SetValue() with MyObject on this, but it errors out with (paraphrased):

对象不是类型

private bool isCollection(PropertyInfo p)
{
    try
    {
        var t = p.PropertyType.GetGenericTypeDefinition();
        return typeof(Collection<>).IsAssignableFrom(t) ||
               typeof(Collection).IsAssignableFrom(t);
    }
    catch
    {
        return false;
    }
    }
}

推荐答案

要使用反射获取/设置，您需要一个实例.要遍历列表中的项目，试试这个:

To Get/Set using reflection you need an instance. To loop through the items in the list try this:

PropertyInfo piTheList = MyObject.GetType().GetProperty("TheList"); //Gets the properties

IList oTheList = piTheList.GetValue(MyObject, null) as IList;

//Now that I have the list object I extract the inner class and get the value of the property I want

PropertyInfo piTheValue = piTheList.PropertyType.GetGenericArguments()[0].GetProperty("TheValue");

foreach (var listItem in oTheList)
{
    object theValue = piTheValue.GetValue(listItem, null);
    piTheValue.SetValue(listItem,"new",null);  // <-- set to an appropriate value
}

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