ArgumentNullException when creating new datarelation

Question

Hi,

I have two unrelated tables in SQL Server. I want to form a relationship with them via C# so the database diagram in SQL Server has the relationship line etc (the code may have flaws apart from the lack of using statements etc, other than that let me know).

I have this code so far:

   SqlConnection con = new SqlConnection("Data Source=localhost;Initial Catalog=Test;Integrated Security=SSPI");

        SqlDataAdapter ad1;
        SqlDataAdapter ad2;

        DataSet ds = new DataSet();
        DataRelation dr;


        ad1 = new SqlDataAdapter("Select * from dept", con);
        ad2 = new SqlDataAdapter("select * from emp", con);
        ad1.Fill(ds, "dept");
        ad2.Fill(ds, "emp");
        DataColumn pk = ds.Tables["dept"].Columns["deptno"];
        DataColumn fk = ds.Tables["emp"].Columns["deptno"];
        dr = new DataRelation("rel", pk, fk, false)
        ds.Relations.Add(dr);

        ds.AcceptChanges();
        ad1.Update(ds, "dept");
        ad2.Update(ds, "emp");

When I get to this line:

        dr = new DataRelation("rel", pk, fk, false)

I get this exception:

'column' argument cannot be null. Parameter name: column

Is it possible to actually form relationships in SQL Server this way?

What gives?

Answer 1

Everything looks ok, unless one of the tables does not have the "deptno" column..

You're real close, try this (semi-colon at end of line :)

dr = new DataRelation("rel", pk, fk, false);

As far as these changes going back to the database, as JWL_ started to go into, no they don't, here's a blurb from MSDN:

There are many times when your application needs to work with related tables. Although a dataset contains tables and columns as in a database, it does not inherently include a database's ability to relate tables. However, you can create DataRelation objects that establish a relationship between a parent (master) and a child (detail) table based on a common key.

Answer 2

The relationship you declare in code does not end up in the database. It only lives inside your DataSet (at least I think thats the case).