How do you change a connection string dynamically in an object datasource in asp.net?

protected void ObjectDataSource1_ObjectCreated(object sender, ObjectDataSourceEventArgs e)
{
    if (e.ObjectInstance != null)
    {
        SqlConnection conn = new SqlConnection();
        conn.ConnectionString = MyConnectionManager.ConnectionString;
        e.ObjectInstance.GetType().GetProperty("Connection").SetValue(e.ObjectInstance, conn, null);
    }
}

I hope it helps.

I didn't get the above to work but this did:

  if (e.ObjectInstance != null)
  {
    ((ReportPrototype.ReleasedRatingsDataTableAdapters.RatingsViewTableAdapter)e.ObjectInstance).Connection.ConnectionString = ConfigurationManager.ConnectionStrings["RADSDataConnectionString"].ConnectionString;
  }

ObjectInstance is the table adapter which in my case was the type bound to the ObjectDataSource.

Here's an approach that will work for all generated table adapters, using reflection:

void OnObjectDataSourceObjectCreated(object sender, ObjectDataSourceEventArgs e)
{
    if (e.ObjectInstance != null)
    {
        ((SqlConnection)e.ObjectInstance.GetType()
            .GetProperty("Connection", BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance )
            .GetValue(e.ObjectInstance, null)
         ).ConnectionString = ConfigurationManager.ConnectionStrings["MyConnectionString"].ConnectionString;
    }
}

Note that the Connection property Microsoft generates is created as internal (on my VS 2013), so you need to give BindingFlags.NonPublic to GetProperty.

And of course, wire up the ObjectCreated event one way or another:

ObjectDataSource ObjectDataSource1 = new ObjectDataSource();
...
ObjectDataSource1.ObjectCreated += OnObjectDataSourceObjectCreated;