Getting reference to reflection object

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Hi,

Consider this scenario:

C#

class A {
      public B {
          get; set;
      }
}

class B {
     public string name { get; set; }
}

Now I want to get a reference to the B object of the A object.

So I am using PropertyInfo Class to get that but through pi = GetValue();
And that I assume doesn't return the reference but a copy of the object since, after setting the value to the object, it doesn't update the original Class A object.

Here is a code snippet that does the work:

C#

      // _TargetObject is the original A object.
private void SyncFieldChanges(string changed_field_id)
{
     PropertyInfo so;
     PropertyInfo to;
     object lv;
     object tw = null;

     try
     {
         to = GetNestedProperty(ref _TargetObject, FindTargetPropertyId(changed_field_id),ref tw);
         so = this.GetType().GetProperty(changed_field_id);

         lv = so.GetValue(this, null);
         to.SetValue(tw, lv, null);
     }
     catch { }

}

PropertyInfo GetNestedProperty(ref object target_object, string nested_property,ref object obj_to_write)
{
     object to;
     string tmp = "";
     string[] np;
     PropertyInfo pi = null;

     obj_to_write = null;

     if(string.IsNullOrEmpty(nested_property)) { return null; }
     np = nested_property.Split('.');
     if (np == null || (np.Length < 2)) 
     {
          pi = target_object.GetType().GetProperty(nested_property);
//This is where the obj_to_write after final recursion is set            
          obj_to_write = target_object;
          return pi;
     }

     for (int i = 1; i < np.Length; i++)
     {
          pi = target_object.GetType().GetProperty(np[i - 1]);

  //CULPRIT - Since in the next recursion call the reference to the to object is passed and to is fetched through GetValue...
          to = pi.GetValue(target_object,null);

          for(int j = i; j < np.Length; j++)
          {
              tmp += np[j] + (j + 1 == np.Length ? "" : ".");
          }
          pi = GetNestedProperty(ref target_object, tmp,ref obj_to_write);
      }
            
   return pi;
}

//--The function returns PropertyInfo object to the nested property, and obj_to_write should be the object just before the farthest nested property, the obj_to_write should point to B object inside A object, and it does that but I think the culprit is above (marked 'CULPRIT' :D) because pi.GetValue returns an object's value not a reference to that object (assumption).
This function is recursive so it might be a little hard to understand...

C#

//--This i just helper function for locating property names  
private string FindTargetPropertyId(string key)
{
     string rv = "";
     KeyValuePair&lt;string, string&gt; kvp;
     kvp = FieldLinks.Find(delegate(KeyValuePair&lt;string, string&gt; o) { return o.Key == key; });
     rv = kvp.Value;
     return rv;
}

Any ideas how to get a reference to an object?

Posted 4-Jul-10 21:23pm

Benny_Lava

Updated 4-Jul-10 21:47pm

Sandeep Mewara

v2

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Keith Barrow · Answer 1 · 2010-07-08T11:42:00

I've really had a time decoding your code so to speak, are you a c++ developer by any chance?

Anyway, I think your algorithm has run-away with itself. Assuming you pass the property name like this "Property1.SubProperty2.Subproperty3", I think you need something like this:

public object FindValue(object rootObject, string properties)
{
  
  List<string> propertyNames = new List <string>(string.Split("."));
  if(string.Length == 0)
    return null;
  return GetValue(rootObject, propertyNames);

}

public object GetValue(object currentObject, List<string>propertyNames)
{
    if(object == null)
     return null;
    if(propertyNames.Count == 0)
     return currentObject;
    PropertyInfo propertyInfo = currentObject.GetType().GetProperty(propertyNames[0]);
    if(propertyInfo == null)
        return null;
    propertyNames.RemoveAt(0);
    object nextObject= propertyInfo.GetValue(currentObject, null);
    return GetValue(nextObject, propertyNames); 
}

Disclaimer: I haven't tested my code & it's getting late here, this code might not be optimal, I think it makes one more iteration than it strictly needs!
propertyInfo.GetValue(currentObject, null) only works for non-indexed values.

Benny_Lava · Answer 2 · 2010-07-09T05:33:00

Thanks Keith,

Well I'm not not a C++ developer (used to be :) developing micro-controller embedded software)

Thank you for your answer although, I have found out the real culprit...

I just didn't see it...

I was passing a structure to my code, and of course structure being a value type is unreflectable in this way...

Actually my code was working from the beginning, just for reference types...

Thanks anyway! :)

Getting reference to reflection object

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