How to find an object property value from a nested

问题:

I have a nested set of objects ie some properties are custom objects. I would like to get a object property value within the hierarchy group using a string for the property name, and some form of "find" method to scan the hierarchy to find a property with matching name, and get its value.

Is this possible and if so how?

Many thanks.

EDIT

Class definition may be in pseudocode:

Class Car
    Public Window myWindow()
    Public Door myDoor()
Class Window
    Public Shape()
Class Door
    Public Material()

Car myCar = new Car()
myCar.myWindow.Shape ="Round"
myDoor.Material = "Metal"

All a little contrived, but could I "find" the value of the "Shape" property by using the magic string "Shape" in some form of find function, starting from the top object. ie:

string myResult = myCar.FindPropertyValue("Shape")

Hopefully myResult = "Round".

This is what I am after.

Thanks.

回答1:

Based on classes you showed in your question, you would need a recursive call to iterate your object properties. How about something you can reuse:

object GetValueFromClassProperty(string propname, object instance)
{
    var type = instance.GetType();
    foreach (var property in type.GetProperties())
    {
        var value = property.GetValue(instance, null);
        if (property.PropertyType.FullName != "System.String"
            && !property.PropertyType.IsPrimitive)
        {
            return GetValueFromClassProperty(propname, value);
        }
        else if (property.Name == propname)
        {
            return value;
        }
    }

    // if you reach this point then the property does not exists
    return null;
}

propname is the property you are searching for. You can use is like this:

var val = GetValueFromClassProperty("Shape", myCar );

回答2:

Yes, this is possible.

public static Object GetPropValue(this Object obj, String name) {
    foreach (String part in name.Split('.')) {
        if (obj == null) { return null; }

        Type type = obj.GetType();
        PropertyInfo info = type.GetProperty(part);
        if (info == null) { return null; }

        obj = info.GetValue(obj, null);
    }
    return obj;
}

public static T GetPropValue<T>(this Object obj, String name) {
    Object retval = GetPropValue(obj, name);
    if (retval == null) { return default(T); }

    // throws InvalidCastException if types are incompatible
    return (T) retval;
}

To use this:

DateTime now = DateTime.Now;
int min = GetPropValue<int>(now, "TimeOfDay.Minutes");
int hrs = now.GetPropValue<int>("TimeOfDay.Hours");

see this link for your reference.