C# Linq to SQL connection string (newbie)

Question

i am a new linq to sql learner and this is my very first attempt to create a data viewer program. The idea is simple, i'd like to create a software that is able to view content of a table in a database. That's it.

I got an early problem here already and i have seen many tutes and articles online but I still cant fix the bug.

Here is my code:

    static void Main(string[] args)
    {
        string cs = "Data Source=localhost;Initial Catalog=somedb;Integrated Security=SSPI;";

        var db = new DataClasses1DataContext(cs);
        db.Connection.Open();

        foreach (var b in db.Mapping.GetTables())
            Console.WriteLine(b.TableName);

        Console.ReadKey(true);
    }

When I tried to check db.connection.equals(null); it returns false, so i thought i have connected successfully to the database since there is no error at all. But the code above doesn't print anything out to the screen.

I kind of lost and don't know what's going on here. Does anyone know what is going wrong here?

How many mappings are there in the data context? Try Console.WriteLine(db.Mapping.GetTables().Count();? A mapping is not the same as a table. — Marijn
– Marijn, Commented Jul 2, 2012 at 7:07
Exactly! There is no mapping at all in the data context, but the count() return a number related to the mappings count that i have after dragging some mappings into the designer. Thanks! — Chris Wijaya
– Chris Wijaya, Commented Jul 3, 2012 at 23:34

Amy B · Accepted Answer · 2012-07-02 14:14:52Z

3

Ok, let's look at some of these lines:

var db = new DataClasses1DataContext(cs);

This is a perfectly normal and fine call to a constructor. Since DataContext implements IDisposable, when you are using it for real, consider using the using statement.

using (var db = new DataClasses1DataContext(cs))
{
  // do stuff with db here
} // when leaving the block, db is disposed - even in the case of an exception.

db.Connection.Open();

Don't do this. DataContext will open and close the connection when it needs to.

foreach (var b in db.Mapping.GetTables())
  Console.WriteLine(b.TableName);

Hmm, maybe there are no tables in the mapping. Did you drag a table onto the designer surface from the server explorer?

Most people would query a table instead of perusing the mappings. Consider this code instead:

foreach (var customer in db.Customer.Take(10))
{
  Console.WriteLine(customer.Name); 
}

Here's a video showing how to drag a table onto the designer surface from the server explorer:

http://www.youtube.com/watch?v=z9L11qrw9gk

edited Jul 2, 2012 at 14:14

answered Jul 2, 2012 at 14:08

Amy B

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1 Comment

Chris Wijaya Over a year ago

All the things you said are true! I didn't add any table in the mapping so gettables.count() returned 0. Big thanks!

uowzd01 · Accepted Answer · 2012-07-02 03:08:46Z

1

Try change your connection string to below

string cs = @"Data Source=.\;Initial Catalog=somedb;Integrated Security=SSPI;";

answered Jul 2, 2012 at 3:08

uowzd01

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1 Comment

Chris Wijaya Over a year ago

Thanks for replying my question but no luck after trying it out tho. I did some other combinations of the connection string too, still can't get any data out of it. Seems like i am missing some kind of property to make linq talk to sql server which i can't figure out yet.

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