Accessing object property as string and setting it

Question

I have an instance of the Account class. Each account object has an owner, reference, etc.

One way I can access an accounts properties is through accessors like

account.Reference;

but I would like to be able to access it using dynamic string selectors like:

account["PropertyName"];

just like in JavaScript. So I would have account["Reference"] which would return the value, but I also would like to be able to assign a new value after that like:

account["Reference"] = "124ds4EE2s";

I've noticed I can use

DataBinder.Eval(account,"Reference") 

to get a property based on a string, but using this I can't assign a value to the property.

Any idea on how I could do that?

Answer 1

You need to use Reflection:

PropertyInfo property = typeof(Account).GetProperty("Reference");

property.SetValue(myAccount, "...", null);

Note that this will be very slow.

Answer 2

If they are your own objects you could provide an indexer to access the fields. I don't really recommend this but it would allow what you want.

public object this[string propertyName]
{
    get
    {
        if(propertyName == "Reference")
            return this.Reference;
        else
            return null;
    }
    set
    {
        if(propertyName == "Reference")
            this.Reference = value;
        else
            // do error case here            
    }
}

Note that you lose type safety when doing this.

Answer 3

If you are using .Net 4 you can use the dynamic keyword now.

dynamic foo = account;
foo.Reference = "124ds4EE2s";

Answer 4

I used the reflection method from Richard, but elaborated the set method to handle other types being used such as strings and nulls.

public object this[string propertyName]
{
    get
    {
        PropertyInfo property = GetType().GetProperty(propertyName);
        return property.GetValue(this, null);
    }
    set
    {
        PropertyInfo property = GetType().GetProperty(propertyName);
        Type propType = property.PropertyType;
        if (value == null)
        {
            if (propType.IsValueType && Nullable.GetUnderlyingType(propType) == null)
            {
                throw new InvalidCastException();
            }
            else
            {
                property.SetValue(this, null, null);
            }
        }
        else if (value.GetType() == propType)
        {
            property.SetValue(this, value, null);
        }
        else
        {
            TypeConverter typeConverter = TypeDescriptor.GetConverter(propType);
            object propValue = typeConverter.ConvertFromString(value.ToString());
            property.SetValue(this, propValue, null);
        }
    }
}

The SetValue() function will throw an error if the conversion doesn't work.

Answer 5

You could try combining the indexer with reflection...

public object this[string propertyName]
{
    get
    {
        PropertyInfo property = GetType().GetProperty(propertyName);
        return property.GetValue(this, null);
    }
    set
    {
        PropertyInfo property = GetType().GetProperty(propertyName);
        property.SetValue(this,value, null);
    }
}

Answer 6

First of all, you should avoid using this; C# is a strongly-typed language, so take advantage of the type safety and performance advantages that accompany that aspect.

If you have a legitimate reason to get and set the value of a property dynamically (in other words, when the type and/or property name is not able to be defined in the code), then you'll have to use reflection.

The most inline-looking way would be this:

object value = typeof(YourType).GetProperty("PropertyName").GetValue(yourInstance);
...
typeof(YourType).GetProperty("PropertyName").SetValue(yourInstance, "value");

However, you can cache the PropertyInfo object to make it more readable:

System.Reflection.PropertyInfo prop = typeof(YourType).GetProperty("PropertyName");

object value = prop.GetValue(yourInstance);
...
prop.SetValue(yourInstance, "value");