C Sharp build fails with invalid token text at root level of document

I have a C# Windows Forms project that has a text file name db.config that contains a connection string like:

Data Source=localhost\SQLSRV;Initial Catalog=db;User Id=sa;Password=********;

The properties of the files are:

• Build action: Content
• Copy to Output Directory: Copy always
• Custom Tool: -
• Custom Tool Namespace: -
• File Name: db.config
• Full PathL: c:\path\to\solution\Config\db.config

When I am building the solution I get these two errors:

1. Invalid token 'Text' at root level of document.
2. XML document must contain a root level element

Any idea how on how to fix the build ?