EntityFramework Multiple Queries Multiple DataContexts? Multiple Connections?

I'm new to EF, and for the first time I need to execute multiple queries in the same time, lets say I have my BLL and DAL generated by EF, I also have a viewModel, on the BLL I'm referencing DAL and retrieve data like this:

public Decimal getPrice()
    {
        Decimal x = 0;
        siliconContext = new DAL.Entities();
        var result = from d in siliconContext.SILICONs
                     select d.MIN_PRICE;
        foreach (Decimal d in result)
        {
            x = d;
        }
        return x;
    }

all good, on the viewModel I use just this two lines of code:

Silicon sil = new Silicon();
Price = sil.getPrice();

I assumed that the Context will handle the connection, open the connection, do something and then close it, but now I'm in a situation where in my ViewModel I will reference two BLLs which they are going 开发者_StackOverflow中文版to reference two DALs and of course two different Contexts in the same method, who is going to manage this? is EF 4 is smart enough to open only one connection and let the two - or more - contexts to do their job and then close the connection? here is an example of how my viewModel will look like

Silicon sil = new Silicon();
Price = sil.getPrice();
Glass gl = new Glass();
GlassPrice = gl.getPrice();

First off you need to close the connection of the DataContext.

public Decimal getPrice()
{
    Decimal x = 0;
    using (DAL.Entities siliconContext = new DAL.Entities())
    {
        var result = from d in siliconContext.SILICONs
                     select d.MIN_PRICE;
        foreach (Decimal d in result)
        {
            x = d;
        }
        return x;
    }
}

Secondly if you want to get data from two tables then do the following.

public Decimal getPrice()
{
    Decimal x = 0; 
    using (DAL.Entities siliconContext = new DAL.Entities())
    {
        var result = from d in siliconContext.SILICONs
                     select d.MIN_PRICE;

        var result2 = from d in seliconContext.GLASEs
                      select d.MIN_PRICE;

        //You can then work with results from table GLASE!

        foreach (Decimal d in result)
        {
            x = d;
        }
        return x;
    }
}

You would need to manage the lifetime of your objectcontext for their proper initialization and disposal. For an excellent resource on context lifetime management, refer to http://blogs.msdn.com/b/alexj/archive/2009/05/07/tip-18-how-to-decide-on-a-lifetime-for-your-objectcontext.aspx