Is it possible to create generic class which only accepts a type which has a certain property

Question

I want to create a class "Indicator" that will accept 'Control' and set its 'Image' property.

Since Control doesn't have an Image property, I want to implement a template class ("Indicator") which will only accept classes which have this property (Image).

Is it possible?

Answer 1

We could change the way how an instance of this class is created by adding a private parameterless constructor and another public ctor in which we'll do our type checks:

class Indicator<T> where T : Control
{
    private T _control;

    private Indicator() 
    {
    }

    public Indicator(T control)
    {
       if(control.GetType().GetProperties().All(p => p.Name != "Image" || p.PropertyType != typeof(Image)))
       { 
          throw new ArgumentException("This type of control is not supported");
       }
       this._control = control;
    }
}

Answer 2

You can use reflection to get the property of your object:

public class ImagePropertyModifier 
{
    private PropertyInfo GetImageProperty(object obj)
    {
        var property = obj.GetType().GetProperty("Image");

        if (property == null)
            throw new Exception("Object has no Image property.");

        if (property.PropertyType != typeof(string))
            throw new Exception("Object's Image property is not a string.");

        return property;
    }

    private static string GetImage(object obj)
    {           
        return GetImageProperty(obj).GetValue(obj, null).ToString();
    }        

    private static string SetImage(object obj, string value)
    {
        GetImageProperty(obj).SetValue(obj, value);
    }        
}

Note that this code assumes that Image is a string (path to an image). You can change the type in accordance with your requirements. It is just an example.