can not access foreign key constraint

Hi Group,
i have a foreign key in a table in sql server.i am using a dataset and
populating it with the contents of this table.my problem is that i am not
able to access the foreign key that i cretaed on this table in the
database.i am using a code something like this.if i check the number of
constraints on the table it prints 1,which is nothing but the primary key
constraint on this table,why doesn't it print 2 and show both primary and
foreign key constraint.i have tried most of the combinations in the code
below.
plz help.

DataSet myDataSet = new DataSet("myDataSet");
myDataSet.EnforceConstraints=true;
SqlDataAdapter adpt=new SqlDataAdapter("select * from "+TableName,con);
//adpt.MissingSchemaAction = MissingSchemaAction.AddWithKey;
adpt.FillSchema(myDataSet,SchemaType.Mapped);
Response.Write(myDataSet.Relations.Count);
Response.Write(myDataSet.Tables["Table"].Constraints.Count);
//Response.Write(myDataSet.Tables["dtbl"].Constraints[0].ConstraintName);
//Response.Write(myDataSet.Tables["dtbl"].Constraints[0].GetType());

thanks in advance

--
Rajesh Tiwari