How to create Entity Framework ObjectContext?

Question

I have many DBs in one SQL server. I placed connectionString as template(look at Initial Catalog={0}) into web.config.

<add name="ent" connectionString="metadata=res://*/ent.csdl|res://*/ent.ssdl|res://*/ent.msl;provider=System.Data.SqlClient;provider connection string="Data Source=1.1.1.1;Initial Catalog={0};Persist Security Info=True;User ID=user;Password=pass;MultipleActiveResultSets=True"" providerName="System.Data.EntityClient" />

I want to create the objectContext with correct connectionString. I thought to do the following, CreatObjectContext<SiteEntities>('MySite') but I get error Unable to determine the provider name for connection of type 'System.Data.EntityClient.EntityConnection'.

public T CreatObjectContext<T>(string dbName) where T : ObjectContext, new()
{          
       var conStr = ConfigurationManager.ConnectionStrings["ent"].ConnectionString;
       var entityBuilder = new EntityConnectionStringBuilder(conStr);
       entityBuilder.Provider = "System.Data.SqlClient";
       // Build correct conString to the db
       entityBuilder.ProviderConnectionString = string.Format(entityBuilder.ProviderConnectionString, dbName);

       var connection = new EntityConnection(entityBuilder.ConnectionString);                          
       var builder = new ContextBuilder<T>();

       return builder.Create(connection);           
}

What I'm doing wrong? How I can create the context?

score 4 · Accepted Answer · answered Aug 31 '11 at 21:15

If you are using EntityConnectionStringBuilder, you only need to store the sqlserver connection strings in your web.config. EntityConnectionStringBuilder can then convert those to EF4 connection strings.

Example web.config

    <connectionStrings>
      <add name="db1" connectionString="data source=localhost\SQLEXPRESS;initial catalog=db1;integrated security=True;multipleactiveresultsets=True;App=EntityFramework" /> 
      <add name="db2" connectionString="data source=localhost\SQLEXPRESS;initial catalog=db2;integrated security=True;multipleactiveresultsets=True;App=EntityFramework" />
    </connectionStrings>

And we can change your method to something like:

public ObjectContext CreatObjectContext(string dbName)
{          
       var conStr = ConfigurationManager.ConnectionStrings[dbName].ConnectionString;
       var entityBuilder = new EntityConnectionStringBuilder();

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

       entityBuilder.MetaData = @"res://*/ent.csdl|res://*/ent.ssdl|res://*/ent.msl";

       return new ObjectContext(entityBuilder.ToString());          
}

Related question entity-framework-runtime-connection-string http://stackoverflow.com/questions/11368897/entity-framework-runtime-connection-string — Michael Freidgeim, May 24 '13 at 20:19

score 2 · Answer 2 · edited May 23 '17 at 11:52

I just wanted to share a small class to create an entity framework connection using the entity class as type of T an SQL connection string and the entityModel meta data name.

    public static class EFConnection<T> where T : ObjectContext
    {
    public static T GetDatabase(string connectionString,string entityModelMetadataName)
    {

        var entityBuilder = new EntityConnectionStringBuilder();
        entityBuilder.Provider = "System.Data.SqlClient";
        entityBuilder.ProviderConnectionString = connectionString;
        entityBuilder.Metadata = @"res://*/" + entityModelMetadataName + ".csdl|res://*/" + entityModelMetadataName + ".ssdl|res://*/" + entityModelMetadataName + ".msl";


    var _db=(T)Activator.CreateInstance(typeof(T), new object[] { entityBuilder.ToString()});
    return _db;

    }

}

use example:

    var _db = EFConnection<Model1Container>.GetDatabase(Settings.General.Default.DatabaseConnectionString, "Model1");

I did use this post also to put everything together:

How to create Entity Framework ObjectContext?

2 Answers2