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alt text csharp-console

CLI REPL utility for evaluating C# statements and expressions and running short programs.

Useful for checking how a fragment of C# code might behave or what it returns, how long it takes to execute, or running some logic that you can write in a few lines but don't want to have to create a project and build to execute it.

This utility has evolved slowly over years of my need to quickly determine how a given C# statement behaves in various circumstances


Binary available for download at


Requires .Net Framework 4.0.


cscon.exe [options] [c#-expression]
  --help       Display help
  --version    Display version
  -v           Enable verbose mode
  -t           Show Type information
  -F|--framework (version)    Use framework version (2.0, 3.5, 4.0)
  -R|--ref (ref)              Reference assembly (ref)
  -U|--using (using)          Add using section for namespace (using)

Executing cscon without an expression will open an interactive terminal where you can issue commands. If an expression is provided, it will be evaluated as a command, its output will be written to the terminal, and cscon will exit.



  e (code)           -- Evaluate statement and show output
  (code)             -- Execute code as written
  time (code)        -- Execute code and output run duration
  whileinput (code)  -- Execute code in a while loop, taking input
                        from the console to the variable 'input'
                        until input is blank
  verbose (on|off)   -- Enable/disable verbose mode
  typeinfo (on|off)  -- Enable/disable show type info
  (line-num) (line)  -- Set program line at line-num
  list               -- List current program with line numbers
  clear              -- Clear current program
  run                -- Run current program

  framework (version)  -- Compile using specified framework version (defaults to v4.0)
  using (namespace)    -- Add namespace to using list
  listusing            -- List currently used namespaces
  clearusing           -- Clear current using list (resets to using System)
  ref (assembly)       -- Add assembly reference
  listref              -- List currently referenced assemblies
  clearref             -- Clear current reference list (resets to referencing System.dll)

Code Expressions and Examples

Entering code in the terminal (or as the expression argument to cscon) will execute the given code and output the value it returns. If the statement does not return anything, it will instead output null.

Use the e command to evaluate an expression and show the output:

# e new DateTime(2019, 1, 5) - new DateTime(2018, 12, 10)
# e Dns.GetHostEntry("")
System.Net.IPHostEntry(HostName="", Aliases=[], AddressList=[System.Net.IPAddress(])

The time command will output the run duration of the code:

# time float x; for (int i = 0; i < Int32.MaxValue; i++) x = (float)i * (float)i;
Time 00:00:06.0950735

The whileinput command allows you to evaluate a statement against a variety of inputs, and ends when you enter a blank input:

# whileinput Console.WriteLine(string.Format("5 x {0} = {1}", input, 5 * int.Parse(input)));
while> 2
5 x 2 = 10
while> 5
5 x 5 = 25
while> 10
5 x 10 = 50
while> 14
5 x 14 = 70
while> 20
5 x 20 = 100

Enter code with no command to run it as-is. Note that if your code does not return anything, and does not write any text to the console using Console.WriteLine, then only null will be displayed:

# var x = 2; var y = 5; var z = x + y; return z;

Code can also be entered across multiple lines as a single command by ending each non-terminating line with \ backslash :

# var x = 2;\
# var y = 5;\
# var z = x + y;\
# return z;

Compilation errors will also be displayed, but the line/col numbers may not make any sense as the expression is internally wrapped in a program:

# e new DateTime(a, 0, 0)
c:\Users\Luke\AppData\Local\Temp\0ih4pvrw.0.cs(11,31) : error CS0103: The name 'a' does not exist in the current contex

Note: Evaulated statements and variables do not persist between commands, so you must declare and set all variables within a single command.

If you need to use a part of the framework that isn't in the default using list or isn't referenced, you can add namespaces or references using the using and ref commands. The following example references the framework assemblies and namespaces needed to take a screenshot of the primary display and save it to the desktop folder:

# ref System.Drawing.dll
Referenced System.Drawing.dll
# ref System.Windows.Forms.dll
Referenced System.Windows.Forms.dll
# using System.Drawing
Using System.Drawing
# using System.Drawing.Imaging
Using System.Drawing.Imaging
# using System.Windows.Forms
Using System.Windows.Forms
# var bounds = Screen.PrimaryScreen.Bounds; \
# var bmp = new Bitmap(bounds.Width, bounds.Height); \
# var g = Graphics.FromImage(bmp); \
# g.CopyFromScreen(bounds.X, bounds.Y, 0, 0, bounds.Size, CopyPixelOperation.SourceCopy); \
# var filename = DateTime.Now.ToString("yyyy-MM-dd-HH-mm-ss") + ".png"; \
# bmp.Save(Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Desktop), filename), ImageFormat.Png);

By default, the used namespaces are:


and the referenced assemblies are:


Line Editor

A simple numbered line editor is included to allow for writing and editing small programs. The returned value from these programs will be displayed in the same way as the command-less expressions above.

Note: You still need to be aware of scopes and braces, so the syntax when using the line editor will likely end up looking a bit strange.

Take input and respond using the input values:

# 10 Console.Write("What is your name? ");
# 20 var name = Console.ReadLine();
# 30 Console.WriteLine("Hello, " + name +"!");
# 40 return name;
# run
What is your name? Luke
Hello, Luke!

Perform simple file listings or operations:

# 10 foreach (string file in Directory.GetFiles("C:\\Windows", "*.exe")) {
# 20 Console.WriteLine(string.Format("{0} is {1} KB", file, new FileInfo(file).Length / 1024));
# 30 }
# run
C:\Windows\explorer.exe is 3840 KB
C:\Windows\HelpPane.exe is 1030 KB
C:\Windows\hh.exe is 17 KB
C:\Windows\notepad.exe is 240 KB
C:\Windows\regedit.exe is 328 KB
C:\Windows\splwow64.exe is 127 KB
C:\Windows\Twunk_16.exe is 47 KB
C:\Windows\Twunk_32.exe is 68 KB
C:\Windows\winhlp32.exe is 11 KB
C:\Windows\write.exe is 11 KB

Or run a classic infinite loop:

# 10 loop:;
# 20 Console.Write("Hello World!");
# 30 goto loop;
# run
Hello World!Hello World!Hello World!Hello World!Hello World!Hello World!Hello World!... etc.

(The only way to break the above loop is to Ctrl-C or close the terminal, which will lose the program)

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