CODEWITHSUNDEEP
c#
scatman
scatman

Reputation: 14565

Looping through Objects properties

How can i loop over an object's properties and get the value of a property.
i have an object that has several properties filled with data. the user specifies what property he wants to view by providing the name of the property, and i need to search for the property in the object and return its value to the user.
How can i achieve this?
i wrote the following code to get the property but couldn't get the value of that prop: 

 public object FindObject(object OBJ, string PropName)
    {
        PropertyInfo[] pi = OBJ.GetType().GetProperties();
        for (int i = 0; i < pi.Length; i++)
        {
            if (pi[i].PropertyType.Name.Contains(PropName))
                return pi[i];//pi[i] is the property the user is searching for,
                             // how can i get its value?
        } 
        return new object();
    }

Upvotes: 3

Views: 3796

Answers (5)

EggyBach
EggyBach

Reputation: 4228

Try this (code inserted inline):

public object FindObject(object OBJ, string PropName)
{
    PropertyInfo[] pi = OBJ.GetType().GetProperties();
    for (int i = 0; i < pi.Length; i++)
    {
        if (pi[i].PropertyType.Name.Contains(PropName))
        {
            if (pi[i].CanRead)                     //Check that you can read it first
               return pi[i].GetValue(OBJ, null);   //Get the value of the property
        }
    }
    return new object();
}

Upvotes: 8

sheikhjabootie
sheikhjabootie

Reputation: 7376

You call the PropertyInfo.GetValue method passing in the object to get the value for. 

public object FindObject(object OBJ, string PropName)      
{          
    PropertyInfo[] pi = OBJ.GetType().GetProperties();           

    for (int i = 0; i < pi.Length; i++)           
    {               
        if (pi[i].Name == PropName)                   
        {
            return pi[i].GetValue(OBJ, null);
        }
    }            

    return new object();       
}

All reflection types, including PropertyInfo are bound to the class. You have to pass in the instance of the class in order to get any instance-related data.

Upvotes: 0

Lloyd
Lloyd

Reputation: 1324

public static object FindObject(object obj, string propName)
{
    return obj.GetType().GetProperties()
        .Where(pi => pi.Name == propName && pi.CanRead)
        .Select(pi => pi.GetValue(obj, null))
        .FirstOrDefault();
}

Upvotes: 1

Felice Pollano
Felice Pollano

Reputation: 33272

pi[i].GetValue(OBJ,null); is the function to use.

Upvotes: 2

Jon Skeet
Jon Skeet

Reputation: 1503944

To get the value from a PropertyInfo, you call GetValue :) I doubt that you really want to be getting the name of the property type mind you. I suspect you want:

if (pi[i].Name == PropName)
{
    return pi[i].GetValue(OBJ, null);
}

Note that you should probably make sure that the property isn't an indexer, and is readable and accessible etc. LINQ is a good way of filtering things, or you could just use Type.GetProperty to get straight to the property with the required name, instead of looping - and then perform all the validation that you need.

You should also consider following naming conventions and using a foreach loop. Oh, and I'd probably either return null or throw an exception if the property can't be found. I can't see how returning a new empty object would be a good idea.

Upvotes: 6

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