‘System.Net.WebPermission, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed

In WPF browser application follow given steps to give full trust permission

1. Select project

2. Right click and select properties.

3. Select security tab from left panel.

4. Now select/ check the radio button that says " This is full trust application"

5. Save and run application.

This will solve ur problem of permission on System.Net.WebPermission.