.net - SQLite EF6 programmatically set connection string at runtime

Question

I try to migrate form EF 3.5 to 6 (with SQLite as database). We can not set the connection string in the app config file (this works without problems with ef6). We have to set connection string programmatically at runtime (after user has selected the SQLite file).

Here is our app.config

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <configSections>
    <!-- For more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 -->
    <section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
  </configSections>
  <connectionStrings>
    <add name="testContext" connectionString="data source=Dataestdb.sqlite;Foreign Keys=True"
      providerName="System.Data.SQLite" />
  </connectionStrings>
  <entityFramework>
    <defaultConnectionFactory type="System.Data.Entity.Infrastructure.LocalDbConnectionFactory, EntityFramework">
      <parameters>
        <parameter value="v11.0" />
      </parameters>
    </defaultConnectionFactory>
    <providers>
      <provider invariantName="System.Data.SQLite" type="System.Data.SQLite.EF6.SQLiteProviderServices, System.Data.SQLite.EF6" />
    </providers>
  </entityFramework>
  <system.data>
    <DbProviderFactories>
      <remove invariant="System.Data.SQLite" />
      <remove invariant="System.Data.SQLite.EF6" />
      <add name="System.Data.SQLite" invariant="System.Data.SQLite" description=".Net Framework Data Provider for SQLite (Entity Framework 6)" type="System.Data.SQLite.EF6.SQLiteProviderFactory, System.Data.SQLite.EF6" />
    </DbProviderFactories>
  </system.data>
</configuration>

Here ist the DbContext

public class FirmwareContext : DbContext
{
    public FirmwareContext()
        : this(DEFAULT_CONNECTION)
    {

    }

    public FirmwareContext(string connextionNameOrString)
        : base(connextionNameOrString)
    {

    }
}

If I connect with the connecation name from app.config all works without problems. If I try to pass the connection string with the second constructor this fails

Here is small example

SQLiteConnectionStringBuilder builder =
    factory.CreateConnectionStringBuilder() as SQLiteConnectionStringBuilder;
builder.DataSource = dataSource; // Path to file name of the user
builder.ForeignKeys = true;

var context = new FirmwareContext(builder.ToString());

var context = new FirmwareContext(builder.ToString());
var test = context.Firmware.FirstOrDefault();

I got the following exception ("Schlüsselwort wird nicht unterstützt: 'foreign keys'.") => The key 'foreign key' is nott supported. If I remove the foreign key set, I got the following exception ("The provider did not return a ProviderManifestToken string.") and some inner exceptions.

It seems that the bas(connectionString) build the MSSQL connection string and for SQLite.

How can I make my second constructor campatible with sqlite?

Answer 1

I was having the same problem. I found a workaround by using a different constructor from the base DbContext class:

public DbContext(DbConnection existingConnection, bool contextOwnsConnection);

Using this override you can pass an SQLiteConnection instead which you set the connection string on. So for example you can add a new constructor to your FirmwareContext.

public FirmwareContext(string connectionString)
    : base(new SQLiteConnection() { ConnectionString = connectionString }, true)
{
}

Or even

public FirmwareContext(string filename)
    : base(new SQLiteConnection() { ConnectionString =
            new SQLiteConnectionStringBuilder()
                { DataSource = filename, ForeignKeys = true }
            .ConnectionString }, true)
{
}