Entity Framework 6 set connection string runtime

Question

We are in a mixed environment where our application is using both ADO.NET and Entity Framework.
Since both are pointing to the same physical SQL server, we would like to

Answer 1

You can work at design time using the connection string in your config file.

<add name="DWContext" connectionString="metadata=res://*/Database.DWH.DWModel.csdl|res://*/Database.DWH.DWModel.ssdl|res://*/Database.DWH.DWModel.msl;provider=System.Data.SqlClient;provider connection string=&quot;data source=SQLSERVER_INSTANCE;initial catalog=DB_NAME;integrated security=True;MultipleActiveResultSets=True;App=EntityFramework&quot;" providerName="System.Data.EntityClient" />

So don't remove it because you need it ONLY at design time.

Work instead in a dynamic way at runtime using this approach (similar to your last one):

Extend the data context partial class:

public partial class DWContext
{
    public DWContext(string nameOrConnectionString)
        : base(nameOrConnectionString)
    {
    }

    /// <summary>
    /// Create a new EF6 dynamic data context using the specified provider connection string.
    /// </summary>
    /// <param name="providerConnectionString">Provider connection string to use. Usually a standart ADO.NET connection string.</param>
    /// <returns></returns>
    public static DWContext Create(string providerConnectionString)
    {
        var entityBuilder = new EntityConnectionStringBuilder();

        // use your ADO.NET connection string
        entityBuilder.ProviderConnectionString = providerConnectionString;

        entityBuilder.Provider = "System.Data.SqlClient";

        // Set the Metadata location.
        entityBuilder.Metadata = @"res://*/Database.DWH.DWModel.csdl|res://*/Database.DWH.DWModel.ssdl|res://*/Database.DWH.DWModel.msl";

        return new DWContext(entityBuilder.ConnectionString);
    }

}

And from your code create a new EF data context with:

private DWContext db = DWContext.Create(providerConnectionString);

Ciao ;-)

Answer 2

Other way is to declare another connection string in the config file and use it with the following alternative constructor:

class TestEntities : DbConnect {
 
    public TestEntities (string connectionName)
       : base($"name={connectionName}")
    {
    }

...

Then to use this solution just:

1. add another connection to the config file:

 <add name="other" connectionString="metadata=res://*/Data.TestEntities .csdl|res://*/Data.TestEntities .ssdl|res://*/Data.TestEntities .msl;provider=System.Data.SqlClient;provider connection string=&quot;data source=...;initial catalog=...;integrated security=True;MultipleActiveResultSets=True;App=EntityFramework&quot;" providerName="System.Data.EntityClient" />

2. call it like this:

   var db = new TestEntities (connectionName:"other");
   

Answer 3

You are getting the Code First mode exception because you are passing a DbConnection built with the ADO.NET connection string. This connection string does not include references to metadata files, so EntityFramework does not know where to find them.

To create a DbContext with an appropriate programmatically set connection string, use the EntityConnectionStringBuilder class.

var entityBuilder = new EntityConnectionStringBuilder();

// use your ADO.NET connection string
entityBuilder.ProviderConnectionString = conString;

// Set the Metadata location.
entityBuilder.Metadata = @"res://*/Model.csdl|res://*/Model.ssdl|res://*/Model.msl";
var dbContext = new DbContext(entityBuilder.ConnectionString);