C#: Introduction for Developers

1. Neal Stublen nstublen@jccc.edu C#: Introduction for Developers

2. How does XMLReader work? • XmlReader.Read() • Advances to next node • XmlReader properties access node name, value, attributes, etc. • Returns false if there are no additional nodes

3. Reading XML Files XmlReader r = XmlReader.Create(path, settings); r.ReadToDescendant(nodeName); do { r.ReadStartElement(nodeName); r.ReadElementContentAsString(); } while (r.ReadToNextSibling(nodeName)); r.Close();

4. Code Practice • Create a new project called CustomerImport • Import Customers into a List<> from any .xml file • Fill a TreeView with the Customer data

5. Review • TreeView • XmlReader

6. LINQ

7. var Data Type • We can declare a variable as type “var” instead of using a specific data type The compiler assigns an implicit data type at compile-time (not run-time) var value = 0; var array = new string[10]; var list = new List<Customer>(); varstr = "Hello"; // str is string type str = 6; // can’t assign int

8. What’s LINQ? • SQL-like query expression on any enumerable object type int[] numbers = new int[100]; for (int index = 0; index < 100; ++index) { numbers[index] = index; } var odds = from number in numbers where number % 2 != 0 select number;

9. Try it in LINQPad • Duplicate code from previous slide • Filter out prime numbers from array using LINQ query

10. LINQ Expressions from [type] element in collection join element2 in collection2 on key1 equals key2 where condition // any boolean expression orderby expression [ascending|descending] select columnExpression select new [type] { name=value, name=value }

11. LINQ Expressions from cust in customers join invoice in invoices on cust.CustomerID equals invoice.CustomerID where invoice.InvoiceDate < sixtyDaysAgo orderbyinvoice.InvoiceTotal descending select

12. Try it with CustomerImport • Create a List<Customer> object by looping through SqlDataReader • Perform LINQ queries on List<Customer>

13. LINQ-to-SQL

14. LINQ-to-SQL • Create objects that represent database entities • Use the same LINQ query expressions against a database • Just restricts “where” clause to SQL-compatible operations

15. See It In Action

16. LINQ on Database Objects • Add LINQ data objects to a project • Drop tables from Server Explorer • Use the new DB to query the database using LINQ • Insert, Update, Delete objects, db.SubmitChanges() • Add related items, db.SubmitChanges() • Paging: (from…).Skip(5).Take(5)

17. LINQ’d Customer-Invoice List • Using LINQ objects, fill a list view with all invoices sorted by CustomerName

18. Context Sensitive Help

19. ToolTips and HelpProviders • Add ToolTip control • Set ToolTip property on each control and/or the form • Hover over control to show tool tip • Add HelpProvider control • Set the HelpString on each property and/or the form • Press F1 while the control has focus to show help string

20. Tab Control

21. Tab Control • Separate panels to group items • Tab across edge changes panel visibility