Web Part Error -- The type is not registered as safe

I’ve been working on a SharePoint 2010 web part project and when I pressed F5 to debug, I ran across the error: “A Web Part or Web Form Control on this Page cannot be displayed or imported. The type is not registered as safe.”

This can be caused by innocently renaming your assembly/namespaces/classes. The first thing to check is: SharePointProjectItem.spdata. Your web part should be properly referenced in the SafeControl section.

 
 
   
 

You can also get this error if you've added a web part to a page (e.g., debugging) and then the web part has been removed from the gallery.

If that doesn't resolve it, check your other files.

e.g. VisualWebPart1.webpart file:

 
VisualWebPart1.ascx.cs namespace name
namespace VisualWebPartProject2.VisualWebPart1
{
    public partial class VisualWebPart1UserControl : UserControl
    {
   
VisualWebPart1.ascx
<%@ Control Language="C#" AutoEventWireup="true" CodeBehind="VisualWebPart1UserControl.ascx.cs" Inherits="VisualWebPartProject2.VisualWebPart1.VisualWebPart1UserControl" %>

VisualWebPart1.cs
namespace VisualWebPartProject2.VisualWebPart1
{
    [ToolboxItemAttribute(false)]
    public class VisualWebPart1 : WebPart
   
Elements.xml

 
Assemblyinfo.cs
[assembly: AssemblyTitle("VisualWebPartProject2")]
...
[assembly: AssemblyProduct("VisualWebPartProject2")]