Connection string for using SQL Server Compact with Entity Framework?

Question

I'm done trying to Google for this. I have installed SQL Server CE 4.0, and have EF 4.1, but I can't get a proper connection string. Nothing on connectionstrings.com applies to me.

I just want to create a SqlCeEngine object, but no matter what I try I get some exception. Most recently it's been

Unknown connection option in connection string

with either "metadata", "app", "provider", or "provider connection string" after it. I know EF requires metadata in the connection string. And I can't imagine how anything could do without "provider connection string".

So far I have this:

<add name="DBContext" 
     connectionString="provider connection string=&quot;Data Source=MyDbFile.sdf;Persist Security Info=False;&quot;" 
     providerName="System.Data.EntityClient" />

At one point I had it with metadata:

<add name="DBContext" 
     connectionString="metadata=res://*/Data.DBContext.csdl|res://*/Data.DBContext.ssdl|res://*/Data.DBContext.msl;provider=System.Data.SqlClient;provider connection string=&quot;Data Source=MyDbFile.sdf;Persist Security Info=False;&quot;" 
     providerName="System.Data.EntityClient" />

Does it need metadata or not? What goes in the "app" part of the connection string? What should the provider be, System.Data.SqlClient or some SQL Server CE version? (which I still can't find when I try to add references. My add references window still only contains System.Data.SqlServerCe version 3.5.1.0.) Or nothing?

And what should go in the providerName attribute? Is System.Data.EntityClient correct? It's like there are 10 different variables here and every combination gives me a new equally mysterious error, none of which turns up anything useful on Google. I'm at my wits' end. Is this even possible?

Answer 1

You could try this in your App.config file (EF5 Code first migrations and SQL Server CE 4.0):

<connectionStrings>
    <add name="DefaultConnection"
         providerName="System.Data.SqlServerCe.4.0"
         connectionString="Data Source=|DataDirectory|\Data\ProjectDb.sdf"/>
</connectionStrings>

And in you ProjectDb class:

class ProjectDb : DbContext
{
    public ProjectDb()
        : base("DefaultConnection")
    {

    }
}

It will work like a charm.

You can find more information here: http://blogs.msdn.com/b/adonet/archive/2011/01/27/using-dbcontext-in-ef-feature-ctp5-part-2-connections-and-models.aspx

Answer 2

I’d stuck with the same problem on Entity Framework 5.0 Code First approach with SQL Server Compact Edition 4.0

To solve it I pass instance of SqlCeConnection to DbContext's constructor:

public class Storage : DbContext
{
    public Storage()
        : base(new SqlCeConnection("Data Source=Database.sdf;Persist Security Info=False;"),
             contextOwnsConnection: true)
    { }

    //...
}

If you don’t want to inline connection string you could get it from App.config through ConfigurationManager And of course you should add reference to the right version of System.Data.SqlServerCe (look inside Extentions tab in the Add Reference dialog)

Answer 3

This TechNet article outlines the steps for using EF with SQL Server Compact. This line jumped out at me, and may solve your problems:

make sure that provider=System.Data.SqlServerCe.3.5 in the connection string.

(I would assume that you would want 4.0 instead of 3.5)

Give that a try and see how things go.

Answer 4

The Lu55's solution didn't work for me, but I found fow to fix it. To still use the automatic code generation (which can overwrite changes in a generated file), I added one more file with the following code:

using System.Data.Entity;
using System.Data.Objects;

namespace MyProject.Data
{
    internal partial class Entities : DbContext
    {
        public Entities(string connectionString)
            : base(
                new ObjectContext(
                        @"metadata=res://*/Data.Model.csdl|
                                   res://*/Data.Model.ssdl|
                                   res://*/Data.Model.msl;
                          provider=System.Data.SqlServerCe.4.0;"),
                true)
        {
            Database.Connection.ConnectionString = connectionString;
        }
    }
}

Answer 5

You have mixed a bit.

For SQL Server CE connection string can be quite easy (possibly replace DbContext with YourNameSpace.DbContextName):

<add name="DbContext" 
     connectionString="MyDbFile.sdf" 
     providerName="System.Data.SqlServerCe.4.0" />

I also had a lot of trouble with connections, so I did the following:

• installed Entity Framework for SQL Server CE
• Checked that web.config contains provider with invariant System.Data.SqlServerCe.4.0
• Verified that there are NO string fields (which will be represented as columns in db) with length max or mode than 4000 symbols (to add restriction use annotation [MaxLength(4000)], by default == MAX)

Metadata are necessary when you use database-first model instead of code-first, so there is .edmx file which represents generated model of the database.