clr exception handling and memory manage.

1. Effective .NET Framework based Development: Exception Handing and Memory Management Brad Abrams Lead Program Manager Common Language Runtime Team Microsoft Corporation [email_address] http:// blogs.msdn.com /brada

8. Performance (continued) int i; try { i = Int32.Parse(“123”); } catch (FormatException ) { Console.WriteLine (“Invalid”); } int i; if (!Int32.TryParse (“123”, out i)) { Console.Writeline(“Invalid”); }

22. Implementing IDisposable public class Resource: IDisposable { private bool disposed = false; pubic int GetValue () { if (disposed) throw new ObjectDisposedException(); // do work } public void Dispose() { if (disposed) return; Dispose(true); GC.SuppressFinalize(this); } protected virtual void Dispose(bool disposing) { if (disposing) { // Dispose dependent objects disposed = true; } // Free unmanaged resources } ~Resource() { Dispose(false); } }

26. Using Statement (3) static void Copy(string sourceName, string destName) { Stream input = File.OpenRead(sourceName); Stream output = File.Create(destName); try { byte[] b = new byte[65536]; int n; while ((n = input.Read(b, 0, b.Length)) != 0) { output.Write(b, 0, n); } } finally { output.Close(); input.Close(); } }

27. Using Statement (4) static void Copy(string sourceName, string destName) { Stream input = File.OpenRead(sourceName); try { Stream output = File.Create(destName); try { byte[] b = new byte[65536]; int n; while ((n = input.Read(b, 0, b.Length)) != 0) { output.Write(b, 0, n); } } finally { output.Close(); } } finally { input.Close(); } }

30. Resource Management 2.0 Feature: MemoryPressure class Bitmap { private long _size; Bitmap (string path ) { _size = new FileInfo(path).Length; GC.AddMemoryPressure(_size); // other work } ~Bitmap() { GC.RemoveMemoryPressure(_size); // other work } }

32. Resource Management 2.0 Feature: HandleCollector static readonly HandleCollector GdiHandleType = new HandleCollector( “GdiHandles”, 10, 50); static IntPtr CreateSolidBrush() { IntPtr temp = CreateSolidBrushImpl(…); GdiHandleType.Add(); return temp; } internal static void DeleteObject(IntPtr handle) { DeleteObjectImpl(handle); GdiHandleType.Remove(); }

34. Back up

36. On Error vs. Try/Catch/Finally Try '<code that may fail> Catch ex As Exception '<error handling code> Finally '<clean up> End Try fReRaise = False OnError GoTo ErrHandler '<code that may fail> GoTo CleanUp ErrHandler: If '<condition we can handle> Then '<error handling code> Else fReRaise = True End If CleanUp: If fReRaise Then Err.Raise errNum OnError GoTo ErrHandler '<code that may fail> ErrHandler: If '<condition we can handle> Then '<error handling code> fReRaise = False Try '<code that may fail> Else fReRaise = True End If CleanUp: If fReRaise Then Err.Raise errNum Catch ex As Exception '<error handling code> Finally '<clean up>