Neal Stublen

Open/Close Connections  ADO.NET uses “connection pooling” to optimize opening and closing connections to the database  cxn.Open() and cxn.Close() are using connections from the connection pool that share the same connection string  ADO.NET manages the actual connection to the database  us/library/8xx3tyca(v=vs.110).aspx us/library/8xx3tyca(v=vs.110).aspx

Think of it like this… class SqlConnectionPool { public SqlConnection Open(string cxnStr) { if (mPool.Contains(cxnString)) { return mPool[cxnString]; } // Create a new connection... }

And… class SqlConnectionPool { public void CheckIdle() { foreach (cxn in mPool) { if (cxn.IsIdle()) { cxn.ReallyClose(); mPool.Remove(cxn); }

DataSets in Class Libraries  Create a DataSet in the class libraries  Select “Referenced DataSets” when adding a DataSet control to a form  Add a BindingSource  Add form controls and bind them to the BindingSource

Designer Walkthrough

Summary  MenuStrip w/ defaults  ToolStrip w/ defaults  StatusStrip  View Menu Toggles  PerformClick()  ToolStripContainer w/ docking  ContextMenuStrip  SplitContainer  ErrorProvider

File System Static Classes  System.IO namespace  Directory CreateDirectory, Exists, Delete  File Exists, Delete, Copy, Move  Path Combine, GetDirectoryName, GetFileName, GetExtension, GetTempFileName DirectorySeparatorChar, VolumeSeparatorChar

File System Instance Classes  DirectoryInfo EnumeratorDirectories(), EnumerateFiles()  FileInfo Name, Length, Open(), OpenText()

File System Exceptions  FileNotFoundException  DirectoryNotFoundException  EndOfStreamException  IOException

Stream Classes  FileStream  StreamReader  StreamWriter  BinaryReader  BinaryWriter

Code Practice  Browse for a text file  Place the filename in a TextBox  Read each line from the file and insert into a ListView  Use two columns in the ListView Line number Content

Review  OpenFileDialog  ImageList  ListView, DetailsView

What’s XML?  Structured data file  Tags identify each data element  Tags can have attributes and child tags   Having Fun in Kansas City  

XML Tags  Elements are identified by start tags,, and end tags,  Content can be placed between tags in the form of text or additional elements  Elements can be described using a single tag,  Comments are tags in the form,

Tag Attributes  In addition to content, each tag can also contain zero, one, or more attributes instead of child elements:

Working with XML Files  Any text editor can be used to create XML files  Visual Studio helps create and edit XML files Creates XML declaration Color coded tags Automatic indentation and closing tags Expanding and collapsing tags

XmlReader/XmlWriter  System.XML is the namespace that contains XML classes  Useful for exporting and importing data in a common format

Writing XML Files XmlWriter w = XmlWriter.Create(path, settings); w.WriteStartDocument(); // A start tag w.WriteStartElement(root_name); // A nested start tag w.WriteStartElement(parent_name); // An attribute on the parent_name tag w.WriteAttributeString(name, value); // A complete element w.WriteElementString(child_name, value); // End tags for parent_name and root w.WriteEndElement(); w.Close();

Using XMLWriterSettings  Define indentation XmlWriterSettings settings = new XmlWriterSettings(); settings.Indent = true; settings.IndentChars = " ";

Code Practice  Create a new project called CustomerExport  Export the rows from the Customers table to Customers.xml  Consider how you would use SqlConnection, SqlCommand, and SqlReader  Save the XML file on the Desktop as…

XML Format Abeyatunge, Derek 1414 S. Dairy Ashford North Chili NY

Review  MemoryStream  XmlWriter  SqlDataReader “inspection”  System.Environment.GetFolderPath  FileStream  Debugging visualizers