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.TH csharp 1 "4 September 2008"
.SH NAME 
csharp \- Interactive C# Shell 
.SH SYNOPSIS
.B csharp 
[options] 
.SH DESCRIPTION
The 
.I csharp
is an interactive C# shell that allows the user to enter and evaluate
C# statements and expressions from the command line.
.PP
This command is a shortcut to invoke the 
.I gmcs
command with the 
.I \-\- shell 
command line option.   All of the regular compiler options available
to gmcs are available in the interactive shell.
.SH OPERATION
Once you launch the csharp command, you will be greeted with the
interactive prompt:
.PP
.nf
$ csharp
Mono C# Shell, type "help;" for help
 
Enter statements below.
csharp>
.fi
.PP
A number of namespaces are pre-defined with C# these include System,
System.Linq, System.Collections and System.Collections.Generic.
Unlike the compiled mode, it is possible to add new using statements
as you type code, for example:
.PP
.nf
csharp> new XmlDocument ();
<interactive>(1,6): error CS0246: The type or namespace name `XmlDocument' could not be found. Are you missing a using directive or an assembly reference?
csharp> using System.Xml;
csharp> new XmlDocument (); 
System.Xml.XmlDocument
.fi
.PP
Every time a command is typed, the scope of that command is one of a
class that derives from the class Mono.CSharp.InteractiveBase.   This
class defines a number of static properties and methods.   To display
a list of available commands access the `help' property:
.nf
csharp> help;
"Static methods:
  LoadPackage (pkg); - Loads the given Package (like -pkg:FILE)
  [...]
  ShowVars ();       - Shows defined local variables.
  ShowUsing ();      - Show active using decltions.
  help;
"
csharp>
.fi
.PP
When expressions are entered, the C# shell will display the result of
executing the expression:
.PP
.nf
csharp> Math.Sin (Math.PI/4); 
0.707106781186547
csharp> 1+1;
2
csharp> "Hello, world".IndexOf (',');
5
.fi
.PP
The C# shell uses the ToString() method on the returned object to
display the object, this sometimes can be limiting since objects that
do not override the ToString() method will get the default behavior
from System.Object which is merely to display their type name:
.PP
.nf
csharp> var a = new XmlDocument ();
csharp> a;
System.Xml.Document
csharp> csharp> a.Name;    
"#document"
csharp>
.fi
.PP
A few datatypes are handled specially by the C# interactive shell like
arrays, System.Collections.Hashtable and are rendered specially
instead of just using ToString ():
.PP
.nf
csharp> var pages = new Hashtable () { 
      >  { "Mono",    "http://www.mono-project.com/" },
      >  { "Linux",   "http://kernel.org" } };
csharp> pages;
{{ "Mono", "http://www.mono-project.com/" }, { "Linux", "http://kernel.org" }}
.fi
.PP
.PP
It is possible to use LINQ directly in the C# interactive shell since
the System.Linq namespace has been imported at startup.   The
following sample gets a list of all the files that have not been
accessed in a week from /tmp:
.PP
.nf
csharp> using System.IO;
csharp> var last_week = DateTime.Now - TimeSpan.FromDays (7);
csharp> var old_files = from f in Directory.GetFiles ("/tmp") 
      >   let fi = new FileInfo (f) 
      >   where fi.LastAccessTime < LastWeek select f;
csharp>
.fi
.PP
You can of course print the results in a single statement as well:
.PP
.nf
csharp> using System.IO;
csharp> var last_week = DateTime.Now - TimeSpan.FromDays (7);
csharp> foreach (var old from f in Directory.GetFiles ("/tmp") 
      >   let fi = new FileInfo (f) 
      >   where fi.LastAccessTime < LastWeek select f) 
      >     Console.WriteLine (old);
[...]
csharp>
.fi
.PP
Unlike compiled C#, the type of a variable can be changed if a new
declaration is entered, for example:
.PP
.nf
csharp> var a = 1;
csharp> a.GetType ();
System.Int32
csharp> var a = "Hello";
csharp> a.GetType ();
System.String
csharp> ShowVars ();
string a = "Hello"
.fi
.PP
In the case that an expression or a statement is not completed in a
single line, a continuation prompt is displayed, for example:
.PP
.nf
csharp> var protocols = new string [] {
      >    "ftp",
      >    "http",
      >    "gopher" 
      > };
csharp> protocols;
{ "ftp", "http", "gopher" }
.fi
.PP
Long running computations can be interrupted by using the Control-C
sequence:
.PP
.nf
csharp> var done = false;
csharp> while (!done) { }
Interrupted!
System.Threading.ThreadAbortException: Thread was being aborted
  at Class1.Host (System.Object& $retval) [0x00000] 
  at Mono.CSharp.InteractiveShell.ExecuteBlock (Mono.CSharp.Class host, Mono.CSharp.Undo undo) [0x00000] 
csharp>
.fi
.PP
.SH INTERACTIVE EDITING
The C# interactive shell contains a line-editor that provides a more
advanced command line editing functionality than the operating system
provides.     
.PP
The command set is similar to many other applications (cursor keys)
and incorporates some of the Emacs commands for editing as well as a
history mechanism to 
.PP
.PP
The following keyboard input is supported:
.TP 
.I Home Key, Control-a
Goes to the beginning of the line.
.TP 
.I End Key, Control-e
Goes to the end of the line.
.TP 
.I Left Arrow Key, Control-b
Moves the cursor back one character.
.TP 
.I Right Arrow Key, Control-f
Moves the cursor forward one character.
.TP
.I Up Arrow Key, Control-p
Goes back in the history, replaces the current line with the previous
line in the history.
.TP
.I Down Arrow Key, Control-n
Moves forward in the history, replaces the current line with the next
lien in the history.
.TP
.I Return
Executes the current line if the statement or expression is complete,
or waits for further input.
.TP 
.I Control-C
Cancel the current line being edited.  This will kill any currently
in-progress edits or partial editing and go back to a toplevel
definition.
.TP
.I Backspace Key
Deletes the character before the cursor
.TP
.I Delete Key, Control-d
Deletes the character at the current cursor position.
.TP
.I Control-k
Erases the contents of the line until the end of the line and places
the result in the cut and paste buffer. 
.TP
.I Alt-D
Deletes the word starting at the cursor position and appends into the
cut and paste buffer.    By pressing Alt-d repeatedly, multiple words
can be appended into the paste buffer. 
.TP
.I Control-Y
Pastes the content of the kill buffer at the current cursor position. 
.TP
.I Control-Q
This is the quote character.   It allows the user to enter
control-characters that are otherwise taken by the command editing
facility.   Press Control-Q followed by the character you want to
insert, and it will be inserted verbatim into the command line. 
.SH STATIC PROPERTIES AND METHODS
Since the methods and properties of the base class from where the
statements and expressions are executed are static, they can be
invoked directly from the shell.   These are the available properties
and methods:
.TP
.I void LoadPackage(string package)
Imports the package specified.   This is equivalent to invoking the
compiler with the -pkg: flag with the specified string.
.TP
.I string Prompt { get; set } 
The prompt used by the shell.  It defaults to the value "csharp> ".
.I string ContinuationPrompt { get; set; } 
The prompt used by the shell when further input is required to
complete the expression or statement. 
.TP 
.I void ShowVars()
Displays all the variables that have been defined so far and their
types.    In the csharp shell declaring new variables will shadow
previous variable declarations, this is different than C# when
compiled.   
.I void ShowUsing()
Displays all the using statements in effect.
.SH STARTUP FILES
The C# shell will load all the C# script files and Mono assemblies
located in the ~/.config/csharp directory on Unix.  C# script files
are files that have the extension .cs and they should only contain
statements and expressions, they can not contain full class
definitions (at least not as of Mono 2.0).   Full class definitions
should be compiled into dlls and stored in that directory.
.SH AUTHORS
The Mono C# Compiler was written by Miguel de Icaza, Ravi Pratap,
Martin Baulig, Marek Safar and Raja Harinath.  The development was
funded by Ximian, Novell and Marek Safar.
.SH LICENSE
The Mono Compiler Suite is released under the terms of the GNU GPL or
the MIT X11.  Please read the accompanying `COPYING' file for details.
Alternative licensing for the compiler is available from Novell.
.SH SEE ALSO
gmcs(1), mcs(1), mdb(1), mono(1), pkg-config(1)
.SH BUGS
To report bugs in the compiler, you must file them on our bug tracking
system, at:
http://www.mono-project.com/Bugs 
.SH MAILING LIST
The Mono Mailing lists are listed at http://www.mono-project.com/Mailing_Lists
.SH MORE INFORMATION
The Mono C# compiler was developed by Novell, Inc
(http://www.novell.com, http) and is based on the
ECMA C# language standard available here:
http://www.ecma.ch/ecma1/STAND/ecma-334.htm
.PP
The home page for the Mono C# compiler is at
http://www.mono-project.com/CSharp_Compiler  information about the
interactive mode for C# is available in http://mono-project.com/CsharpRepl