Using C# dll in Windows phone 7 - dllimport

Question

I've tried using C# dll in Windows phone 7 but it occurs error after start debugging as illustrated below.
Troubleshooding tips:
If the access level of a method in a class library has changed, recompile any assemblies that reference that library.
Get generral help for this exception.
This is the code..
-----------------Windows Phone 7-----------------------------------------------
using System;
...
using System.Runtime.InteropServices;
namespace DllLoadTest
{
public partial class MainPage : PhoneApplicationPage
{
// Constructor
public MainPage()
{
InitializeComponent();
}
[DllImport("MathLibrary.dll")]
public static extern int AddInteger(int a, int b);
private void button1_Click(object sender, RoutedEventArgs e)
{
MessageBox.Show("test " + AddInteger(3, 4));
}
}
}
------------------------C# MathLibrary.dll----------------------------------
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace MathLibrary
{
public class Add
{
public static long AddInteger(long i, long j)
{
return i + j;
}
}
}
is there any problem? if not, using C# dll for WindowsPhone7 is impossible?
The C# Dll loaded well in visualstudio2008 C#.

Answer 1

Why are you trying to use P/Invoke on a class library written in C#? Just add a reference to the DLL and use it directly:
using MathLibrary;
...
private void button1_Click(object sender, RoutedEventArgs e)
{
MessageBox.Show("test " + Add.AddInteger(3, 4));
}
You can't use P/Invoke in Windows Phone 7, but you can use class libraries (built for Windows Phone 7).