How to fix Error: "Could not find schema information for the attribute/element" by creating schema

Question

Quickest, easiest laziest way to solve the problem:

1. Right-click on the project icon in Solution Explorer and choose "Properties".
2. Go to the "Application" tab and choose an earlier .NET target framework.
3. Save changes.
4. Go to the "Application" tab and choose the initial .NET target framework.
5. Save changes => problem solved!

UPDATE Sept 2015
This answer continues to get upvotes, so I'm going to leave it here since it seems to be helpful to some people, but please check out the other answers from @reexmonkey and @Pressacco first. They may provide better results.

ORIGINAL ANSWER
Give this a shot:

1. In Visual Studio, open your app.config or web.config file.
2. Go to the "XML" menu and select "Create Schema". This action should create a new file called "app.xsd" or "web.xsd".
3. Save that file to your disk.
4. Go back to your app.config or web.config and in the edit window, right click and select properties. From there, make sure the xsd you just generated is referenced in the Schemas property. If it's not there then add it.

That should cause those messages to disappear.

I saved my web.xsd in the root of my web folder (which might not be the best place for it, but just for demonstration purposes) and my Schemas property looks like this:

"C:\Program Files (x86)\Microsoft Visual Studio 10.0\xml\Schemas\DotNetConfig.xsd" "Web.xsd"

An XSD is included with EntLib 5, and is installed in the Visual Studio schema directory. In my case, it could be found at:

C:\Program Files (x86)\Microsoft Visual Studio 10.0\Xml\Schemas\EnterpriseLibrary.Configuration.xsd

CONTEXT

• Visual Studio 2010
• Enterprise Library 5

STEPS TO REMOVE THE WARNINGS

1. open app.config in your Visual Studio project
2. right click in the XML Document editor, select "Properties"
3. add the fully qualified path to the "EnterpriseLibrary.Configuration.xsd"

ASIDE

It is worth repeating that these "Error List" "Messages" ("Could not find schema information for the element") are only visible when you open the app.config file. If you "Close All Documents" and compile... no messages will be reported.

I found that there was a syntax error in the related module and it wasn't compiling - the compiler didn't tell me that though. Just gave me the error regarding the app.config stuff. VS2010. Once I had fixed the syntax error, all was good.

This error occurs when your project references out of date schemas. Use Visual Studio to generate new ones.

In Visual Studio, do the following:

1. Open your app.config or web.config file.
2. Go to the XML menu and select Create Schema.

This will trigger app#.xsd (Windows app) or web#.xsd (Website) file(s) to generate.

3. Save the newly generated xsd file(s) to the root of the project.
   • Open up your App.config or web.config file, right-click in the text-editor and select properties and click the ... button next to the value for Schemas.
   • Add the newly generated xsd file(s) using the Add button.
   • Click OK

The Could not find schema information for the attribute/element error(s) should now be resolved.