Dynamically run C# code in the same context

readme.md

Why we cannot use ExpandoObject

C# is not the thing what we thought about like the JavaScript, JavaScript has a global context object for the script running.
But in c# is not so easy (at least the runtime doesn't offer us that function directly).

But, how does csi.exe did it?

csi.exe initializes a CommandLineRunner for command interactive while starting. Then create a global context ScriptState<object> to save the execution results(return value, variables, methods). Once you commit the code to the terminal, it appends your code to the global context and compiles the code, and runs again or shows you the error.

But, some private and internal methods or classes prevent you to do like csi.exe do (ScriptBuilder, CSharpScriptCompiler, Script.CreateInitialScript).

### About the Black Magic It only does two things:

• Initialize the environment for the first time you create the sandbox.
• Grab the internal compiler from runtime.

The update: You now can go without using the black magic.

Use the sandbox

Make sure you have installed Roslyn nuget package.

<PackageReference Include="Microsoft.CodeAnalysis.CSharp.Scripting" Version="4.1.0-3.final" />

then type the code

var sandbox = new SandBox();
{
    dynamic result = await sandbox.RunAsync("return \"Hello world!\"");
    Console.WriteLine(result);
}

You will get a "Hello world!" string output if no exception happens.

SandBox.cs

public class SandBox
{
    private ScriptState<object> _globalState;

    public SandBox()
    {
        // Create initial script
        var script = CSharpScript.Create(string.Empty, ScriptOptions.Default);
        {
            // Create an empty state
            _globalState = script.RunAsync
                (null, _ => true, default).GetAwaiter().GetResult();
        }
    }

    public async Task<object> RunAsync(string code, CancellationToken token = default)
    {
        // Append the code to the last session
        var newScript = _globalState.Script
            .ContinueWith(code, ScriptOptions.Default);

        // Diagnostics
        var diagnostics = newScript.Compile(token);
        foreach (var item in diagnostics)
        {
            if (item.Severity >= DiagnosticSeverity.Error) return null;
        }

        // Execute the code
        _globalState = await newScript
            .RunFromAsync(_globalState, _ => true, token);

        return _globalState.ReturnValue;
    }
}

Dependencies:

Install-Package Microsoft.CodeAnalysis.CSharp.Scripting
Install-Package Microsoft.CodeAnalysis.Scripting.Common

https://gist.github.com/AkulaKirov/dbfd77132bd563dcd69e269ad64b45fe
A fix version for error that GlobalTypes not functional for the script.
replace optionsOpt into globalsTypeOpt at BlackInteractiveMagic.cs , Line 30.

@AkulaKirov I fixed the issue you have noticed. hearty thanks.

if (item.Severity > DiagnosticSeverity.Error) return null; is useless because the highest severity level is Error.

if (item.Severity > DiagnosticSeverity.Error) return null; is useless because the highest severity level is Error.

Oh, I see. I've updated the sample code. thanks!