How to pass an Interface object to a WebMethod?

Question

I have a .Net web service with web method which take a Interface object as parameter, whenever I try to access the method I get exception saying : Cannot serialize member Product IProduct because it is an interface.

Any suggestions to solve the problem ??

[WebMethod]
Public double CalculateTotal(IProduct product, int Quantity)
{
  return product.Price * Quantity;
}

Answer 1

Try adding an XmlInclude attribute to your method:

[WebMethod]
[XmlInclude(typeof(Product))]
Public double CalculateTotal(IProduct product, int Quantity)
{  
    return product.Price * Quantity;
}

Edit

Just incase you are getting confused with my use of the class "Product". Replace this class with whatever class in your assembly that implements IProduct e.g.

[Serializable]
public class Product : IProduct
{
     public Product(string name, double price)
     {
         this.Name = name;
         this.Price = price;
     }

     public string Name { get; private set; }
     public double Price { get; private set; }
}

public interface IProduct
{
    string Name { get; }
    double Price { get; }
}

....

[Web Method]
[XmlInclude(typeof(Product))]
Public double CalculateTotal(IProduct product, int quantity)
{
     return product.Price * quantity;
}

Basically when you pass an interface into a webservice it cannot find any schema for it, hence if you use XmlInclude attribute and pass in the concrete class it will be able to recognise the type.

Answer 2

hi prashant please try to do like this..

In place of this

 [WebMethod]
    Public double CalculateTotal(IProduct product, int Quantity)
    {  
     return product.Price * Quantity;
    }

Just Add an abstract class becoz you need a type to serialize it..

  [Serializable]
  public abstract class ProductAbstract : IProduct
  {
    // define all methods/attributes of interface IProduct here as abstract methods/attributes
  }


    [WebMethod]
    Public double CalculateTotal(ProductAbstract product, int Quantity)
    {  
       return product.Price * Quantity;
    }