Dynamic Programming in C# and Visual Basic

  • Article

This walkthrough shows how the new Dynamic feature in C# 4.0 and Visual Basic 10.0 enables the natural use of object models that expect their host language to provide dynamic dispatch. This capability is demonstrated for an IronPython scenario of accessing libraries that are written for the Python language. Note that more advanced IronPython scenarios that involve hosting your own scripts with access to your application’s object model are beyond the scope of this walkthrough.

Notes:

  • Using Dynamic with Office programming is demonstrated in the Office Programmability walkthrough.
  • Using Dynamic with Silverlight will be shown in a later preview release of Visual Studio 2010.

Prerequisites:

The IronPython scenario uses the following resources:

IronPython Scenario

This walkthrough demonstrates how to access an IronPython library from C#.

To set up an IronPython interop project

1.    Start Visual Studio 2010 and create a new C# console application.

2.    Add references to IronPython.dll, IronPython.Modules.dll, and Microsoft.Scripting.dll (all located in the %PROGRAMFILES%\IronPython 2.6 CTP for .NET 4.0 Beta 1 folder).

3.    Copy the Python Lib folder into the bin\Debug folder for your project. (for example, copy the %PROGRAMFILES%\IronPython 2.6 CTP for .NET 4.0 Beta 1\Lib folder into the C:\IronPythonProject\bin\Debug folder)

4.    Add the following using statements to the top of the Program.cs/Module1.vb file:

using IronPython.Hosting;
using Microsoft.Scripting.Hosting;

Imports IronPython.Hosting
Imports Microsoft.Scripting.Hosting

To import an IronPython module in C#/VB

5.    Add code to create a new ScriptRuntime to represent the hosted IronPython environment. This ScriptRuntime can then be used to load Python code, in this case the library module random, which contains the shuffle function.

Add the following code to the Main method:

Console.WriteLine("Loading random.py...");
ScriptRuntime py = Python.CreateRuntime();
dynamic random = py.UseFile("random.py");
Console.WriteLine("random.py loaded!");
var items = Enumerable.Range(1, 7).ToArray();

Console.WriteLine("Loading random.py...")
Dim py As ScriptRuntime = Python.CreateRuntime()
Dim random As Object = py.UseFile("random.py")
Console.WriteLine("random.py loaded!")
Dim items = Enumerable.Range(1, 7).ToArray()

6.    Add the following code to the end of the Main method, which repeatedly calls the shuffle function to generate random orderings of the items array:

for (int s = 0; s < 10000; s++)
{
    random.shuffle(items);
    Console.Write("Sequence {0}: ", s);
    foreach (int i in items)
    {
        Console.Write("{0} ", i);
    }
    Console.WriteLine();
}

For s As Integer = 1 To 10000
    random.shuffle(items)
    Console.Write("Sequence {0}: ", s)
    For Each i In items
        Console.Write("{0} ", i)
    Next
    Console.WriteLine()
Next

7.    Build and run the application. The Python module random repeatedly shuffles the numbers 1 through 7 in random order 10000 times. Notice that there is a startup cost when the Python runtime is first initialized, but that each iteration of the loop then executes extremely fast.