Keyword not supported: “data source” (Passing Connection String Of Type EF to EF constructor)

Assuming you have a connection string that points to an Entity Framework object. And in your connection class, you pass the connection string to the Entity Framework constructor below:

customerEntity = new Database1Entities(_connectionString);

You encountered an error Keyword not supported: "data source".

The solution is presented here: Keyword not supported data source initializing entity framework context

It suggests to replace the " word with single quote (') character.
So, in this case, I used Regex to perform replace operation.

return Regex.Replace(ConfigurationManager.ConnectionStrings[key].ToString(),  
           @"&quot", "'", RegexOptions.IgnoreCase);