Scripting API Samples

Tomáš Matoušek edited this page Jul 1, 2018 · 33 revisions

The scripting APIs enable .NET applications to instatiate a C# engine and execute code snippets against host-supplied objects. Below are examples of how to get started with the scripting APIs and some common samples. You can also view the Scripting API source code.

Supported Platforms

Scripting APIs require desktop .NET Framework 4.6+, or .NET Core 1.1 (supported since Roslyn v2.0.0-rc3, Visual Studio 2017 RC3).

Scripting APIs can't be used within Universal Windows Applications and .NET Native since the application model doesn't support loading code generated at runtime.

Getting Started

Install the Scripting API NuGet Package:

Install-Package Microsoft.CodeAnalysis.CSharp.Scripting

Code Samples

Note: the samples require the following using:
using Microsoft.CodeAnalysis.CSharp.Scripting;


Evaluate a C# expression

object result = await CSharpScript.EvaluateAsync("1 + 2");

Evaluate a C# expression (strongly-typed)

int result = await CSharpScript.EvaluateAsync<int>("1 + 2");

Evaluate a C# expression with error handling

    Console.WriteLine(await CSharpScript.EvaluateAsync("2+2"));
catch (CompilationErrorException e)
    Console.WriteLine(string.Join(Environment.NewLine, e.Diagnostics));

Add references

var result = await CSharpScript.EvaluateAsync("System.Net.Dns.GetHostName()", 

Add namespace and type imports

In the following code WithImports("System.IO") adds using System.IO; to the script options, making it possible to reference the types of System.IO namespace from the script code without qualification.

var result = await CSharpScript.EvaluateAsync("Directory.GetCurrentDirectory()"), 

Likewise, WithImports("System.Math") adds using static System.Math; to the script options, making it possible to reference the members of System.Math type without qualification.

var result = await CSharpScript.EvaluateAsync("Sqrt(2)", 

Parameterize a script

public class Globals
    public int X;
    public int Y;
var globals = new Globals { X = 1, Y = 2 };
Console.WriteLine(await CSharpScript.EvaluateAsync<int>("X+Y", globals: globals));

Note: Currently the Globals type has to be defined in an assembly loaded from a file. If the assembly is in-memory (including e.g. when the sample is executed in Interactive Window) the script won't be able to access the type. See issue here.

Create & build a C# script and execute it multiple times

var script = CSharpScript.Create<int>("X*Y", globalsType: typeof(Globals));
for (int i = 0; i < 10; i++)
    Console.WriteLine((await script.RunAsync(new Globals { X = i, Y = i })).ReturnValue);

Create a delegate to a script

The delegate doesn’t hold compilation resources (syntax trees, etc.) alive.

var script = CSharpScript.Create<int>("X*Y", globalsType: typeof(Globals));
ScriptRunner<int> runner = script.CreateDelegate();
for (int i = 0; i < 10; i++)
    Console.WriteLine(await runner(new Globals { X = i, Y = i }));

Run a C# snippet and inspect defined script variables

var state = await CSharpScript.RunAsync<int>("int answer = 42;");
foreach (var variable in state.Variables)
     Console.WriteLine($"{variable.Name} = {variable.Value} of type {variable.Type}");

Chain code snippets to form a script

var script = CSharpScript.
    Create<int>("int x = 1;").
    ContinueWith("int y = 2;").
    ContinueWith("x + y");

Console.WriteLine((await script.RunAsync()).ReturnValue);

Continue script execution from a previous state

var state = await CSharpScript.RunAsync("int x = 1;");
state = await state.ContinueWithAsync("int y = 2;");
state = await state.ContinueWithAsync("x+y");

Create and analyze a C# script

using Microsoft.CodeAnalysis;

var script = CSharpScript.Create<int>("3");
Compilation compilation = script.GetCompilation();
//do stuff

Compilation gives access to the full set of Roslyn APIs.

Customize assembly loading

using Microsoft.CodeAnalysis.Scripting.Hosting;

using (var loader = new InteractiveAssemblyLoader())
    var script = CSharpScript.Create<int>("1", assemblyLoader: loader);
    //do stuff 
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