Question

I’m dealing with a C# application using EntityFramework and an object derived from DbContext.
I need to set programmatically the connection string when a new instance of MyDbContext object is created. In order to do so I use the following code:

public MyDbContext(string myString)
{
    this.Database.Connection.ConnectionString = myString
}

myString =  "Server=MYSERVER\\SQLEXPRESS; Database=MyDB; User ID=user; Password=pass;";
or
myString =  "Data Source=|DataDirectory|\\AirecCalcDatabase.sdf";

The database providers are different for the two strings. SQLExpress for the first one, SQLCompact for the second one.
If I try to run this code with the first string, I get ArgumentException coming from the connection string. For example “Keyword not valid: server” but also “Keyword not valid: database”. The connection string works when using the DbContext with no arguments, which is, reading the string from app.config

Answer 1

When you’re wanting to use CE, you may need to change the DefaultConnectionFactory to point to SQL CE:

Database.DefaultConnectionFactory = new SqlCeConnectionFactory("System.Data.SqlServerCe.4.0");

See this blog post for more information