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C#

Local

Gotchas

Best Practices
Bitmap from Resources
CLS Compliance
.dlls, calling funcs in them
Exceptions
Exitting
File I/O
File Open Dialog
Flags (type of Enumeration)
Form, setting its starting position
Gotchas
MessageBox
Parent class, calling one of its methods
Parent, getting its 'this'
Random Notes
Resources
Scope
Strings
Thread Synchronization
using (statement)
Window, Setting its parent to a HWND from outside C#

External

C# for C++ Programmers http://msdn.microsoft.com/msdnmag/issues/01/07/ctocsharp/default.aspx
Icons from files http://support.microsoft.com/?kbid=319350
http://www.c-sharpcorner.com/
C# for ASP.NET Developers http://www.sitepoint.com/article/853/1

Best Practices

WinForms Programming

Move main out of where it is created by default, and into its own file, a good name for the file is Main.cs
Initialize logging in main
Put a Global try catch (that logs) in main

public class App
{
	public static void Main()
	{
		try {
			System.Windows.Forms.Application.ThreadException += System.Thread.ThreadExceptionEventHandler( OnAppException));
			
			string logfile = System.AppDomain.CurrentDomain.BaseDirectory + "TraceLog.txt";
			System.IO.TextWriter log = new System.IO.StreamWriter( logfile);
			
			if ( Globals.Trace) {
				System.Diagnostics.TextWriterTraceListener logger;
				logger = new System.Diagnostics.TextWriterTraceListener( log);
				System.Diagnostics.Trace.Listeners.Add( logger);
				System.Diagnostics.Trace.WriteLine("App starting: " + DateTime.Now);
			}
			
			System.Windows.Form.Application.Run( new MainForm() );
		} catch( Exception ex) {
			App.OnAppException( null, new ST.ThreadExceptionEventArgs(ex));
		}
	}

	private static void OnAppException( Object sender, System.Thread.ThreadExceptionEventArgs e)
	{
		Exception ex;
		ex = e.Exception;
		
		System.Windows.Forms.MessageBox.Show( "Halting due to error: " + ex.Message, "Fatal Error");
		
		T.WriteLine( "Global Exception Handler:");
		while( ex != null) {
			T.WriteLine( ex.GetType().FullName);
			T.Indent();
			T.WriteLine( "ExceptMess: " + ex.Message);
			T.WriteLine( "Trace: " + ex.StackTrace);
			T.Unindent();
			T.Flush();
			
			ex = ex.InnerException;
		}
		
		T.Close();
		System.Windows.Forms.Application.Exit();
	}
}

scope

internal target of this is public to other code in the project, but private to other projects.
public
private

Exceptions

Examples of the 2 types

try {
	throw new MyException();
} catch( MyException e) {
	// handle MyException here
} catch {
	// catch all for any exception type
} finally {
	// Clean up stuff here, even if a return happens from anywhere,
	// Unless the program is terminated in the catch block 
}

List of All Exceptions

In Visual Studio, goto Debug | Exceptions

Some info you can get in a catch about an Exception

System.Diagnostics.EventLog.WriteEntry( "XXX", ex.GetType().FullName);
System.Diagnostics.EventLog.WriteEntry( "XXX", ex.Message);
System.Diagnostics.EventLog.WriteEntry( "XXX", ex.StackTrace);

using (statement)

Use this statement to limit the lifetime of an object.
! I BELIEVE ! that this deletes the object when the scope of the block it is associated with is left.

private void DrawBackground( Graphic g)
{
	using (Brush backBrush = new SolidBrush(BackColor))
	using (Pen borderPen = new Pen(BorderColor, 4))
	{
		g.FillRectangle(backBrush, new Rectangle(10, 10, 50, 50);
		g.DrawRectangle(borderPen, new Rectangle(8, 8, 54, 54);
	}
}

Random Notes

Inspired by Ten Traps in C# for C++ Programmers

#1 Finalize
Finalizer is called when the garbage collector when the object is destroyed
Is never called explicitly
Finalizer should only release _unmanaged_ resources
Don't implement it if you don't need it, there is a cost associated with it
Always call the base classes Finalize()

These are the same:

~MyClass()
{
	// do stuff
}

MyClass.Finalize()
{
	// do stuff
	base.Finalize()
}

#2 Dispose
If you want to do the clean up that Finalize would do you must call Dispose() instead
The Class must implement IDisposable, which has 1 method void Dispose()
Make sure garbage collection does not happen after you do Dispose ( it is not needed since you dumping all unmanaged stuff in Dispose)
the Finalize() method should call the Dispose (for the case where you don't cause it to happen, the garbage collector can make it happen), here is an example:

public void Dispose()
{
	// do stuff
	GC.SuppressFinalize(this); // prevent Garbage collector from calling this objects Finalize()
}

public override void Finalize()
{
	Dispose();
	base.Finalize();
}
If you want something like Close() instead of Dispose(), just make the Dispose() private and have the Close() call Dispose()
The using statement causes the Dispose to be called as soon as possible.

using (MyObject obj = new MyObject())
{
	// use obj
} // obj.Dispose() get called at this point
Note that the Dispose gets called no matter how the scope of the statement after it is called, even if an exception is thrown.


Structs in C#
do support:
properties, methods, fields, and operators
don't support:
inheritance, or destructors

a class is a reference type (no boxing, slower in arrays)
a struct is a value type (needs boxing, good in arrays)

===
Virtual methods must be explicity overriden

public class A
{
	public virtual void method1() {...}
	public virtual void method2() {...}
}

public class B : A
{
	public new virtual void method1() {...} // hides the base class version
	public override virtual void method2() {...} // overrides the base class version
}

If neither is specified, it assumes new and prints a warning.

===
Perform class variable initialization by just setting the value when you declare the variable
No semicolon after a class declaration
Each member declaration must have its own access declaration

class A
{
	int m_i = 3; // initialize here
}


===
case statements

fall through only if the case does nothing
can use goto to fall through if the case did something

switch(i) {
	case 1: // falls through
	case 2:
		xxx = 5;
		goto case 3; // do fall through type behavior
	case 3:
		yyy = 5;
}


===
A case where assignment is not needed

// needed:
int a = 0;
GetValue1( ref a);

// not needed
int b;
GetValue2( out b);

// where
GetValue1( ref v) { return a = 5; }
GetValue2( out int v) { return v = 5; }

.dlls, calling funcs in them

// sort of like this, but you cannot actually use classes, just functions:

[DllImport("apibridge.dll")] public static extern class CBridgeApiClass {};

File I/O

using System;
using System.IO;

TextWriter tw = new StreamWriter( "date.txt");
tw.WriteLine( DateTime.Now);
tw.Close();


TextReader tr = new StreamReader( "date.txt");
Console.WriteLine(tr.ReadLine());
tr.Close();

Strings

String literal without escape sequences @"this \n is not interpreted as newline"
Case insensitive compare String.Compare( str1, str2, true);

Resources

COM interop, when adding these, add from the .dll if possible [there appear to be problems with useing the .tlb]

Gotchas

Some sort of problem going into a COM object that is in the reference list

Remove then re-add the object to references from the place it actually runs from
Seems to happen sometimes when the project that uses the COM Object is moved

Exitting

A Forms Application

// Note this only:
// 1) closes all windows
// 2) exits window message loops
// 3) returns from Application.Run()
// 4) so code after Application.Run() then gets executed (of which there is usually none)
Application.Exit()

A Program

System.Environment.Exit( int nStatus);

Bitmap from Resources

Ruth came up with this method (I think I saw a cleaner method, but neglected to note it):

// To Get it:
System.Reflection.Assembly assm = System.Reflection.Assembly.GetExecutingAssembly ();
System.IO.Stream stream = assm.GetManifestResourceStream ("afoNETExtension.command.bmp");
System.Drawing.Bitmap bitmap = (System.Drawing.Bitmap)System.Drawing.Image.FromStream (stream);
m_HBitmap = bitmap.GetHbitmap ();

// To supply the DeleteObject func from gdi32.dll:
[DllImport("gdi32.dll")]
public static extern bool DeleteObject(IntPtr hObject);

// To Release it:
DeleteObject (m_HBitmap);

Thread Synchronization

// Context-bound type with the Synchronization context attribute.
[Synchronization()]
public class SampleSyncronized : ContextBoundObject {

    // A method that does some work, and returns the square of the given number.
    public int Square(int i)  {

        Console.Write("The hash of the thread executing ");
        Console.WriteLine("SampleSyncronized.Square is: {0}", 
                             Thread.CurrentThread.GetHashCode());
        return i*i;
    }
}

CLS Compliance

Making code with compliant and non compliant parts be compliant:

using System;
// Assembly marked as compliant.
[assembly: CLSCompliantAttribute(true)]
// Class marked as compliant.
[CLSCompliantAttribute(true)]
public class MyCompliantClass {
   // Method marked as not compliant.
   [CLSCompliantAttribute(false)]
   public void ChangeValue(UInt32 value){ }
   public static void Main( ) {
   int i = 2;
   Console.WriteLine(i);
   }
}

Flags (type of Enumeration)

// A bit field enumeration
public enum SupportedSpeeds
{
  none = 0,
  b1200 = 1,
  b9600 = 2,
  b19200 = 4,
  b56000 = 8,
  All = b1200 | b9600 | b19200 | b56000,
}

SupportedSpeeds mySpeeds = b1200 | b19200;

Window, Setting its parent to a HWND from outside C#

[DllImport("user32.dll")]
public extern static int SetParent(int child ,int parent );

void setParent( int parent)
{
  SetParent( form.Handle.ToInt32(), parent);
}

MessageBox

System.Windows.Forms.MessageBox.Show( "Message Goes Here");

Parent, getting its 'this'

Parent classes 'this' is 'base'

Parent class, calling one of its methods

public class Parent
{
	public int getCount() {
		return 5;
	}
}

public class Child : Parent
{
  public int getCount() {
    return 7;
  }
  
  public int getParentsCount() {
		return getCount(); // Bad returns Child Count
		return base.getCount(); // returns parents count
  }
}

Form, setting its starting position

this.StartPosition = FormStartPosition.Manual;
this.Location = new Point( 0, 0);

File Open Dialog

OpenFileDialog dlg = new OpenFileDialog();
dlg.InitialDirectory = "C:\\";
dlg.Filter = "Images|*.img|All files|*.*";
if ( dlg.ShowDialog(this) == DialogResult.OK) 
{
}