I am having trouble linking to a secondary class in my project - I have attached 2 images which describe the problem best..

Pleas any advice - I thank you in advance.

![enter image description here](https://i.stack.imgur.com/f0t57.png)
![enter image description here](https://i.stack.imgur.com/5e8uO.png)

This error was two things - thank you everybody for your help.
1) add namespace to DB file

```
namespace C_Classes

```

{
 using System;
 ...

```
public class DB

```

2) Change Target Framework in the Project Properties and change it to ".Net Framework 4" from "...Client Profile"