Compile and run dynamic code, without generating EXE?

Question

I was wondering if it was possible to compile, and run stored code, without generating an exe or any type of other files, basically run the file from memory.

Basically, the Main application, will have some stored code (code that will potentially be changed), and it will need to compile the code, and execute it. without creating any files.

creating the files, running the program, and then deleting the files is not an option. the compiled code will need to be ran from memory.

code examples, or pointers, or pretty much anything is welcome :)

Answer 1

using (Microsoft.CSharp.CSharpCodeProvider foo = 
           new Microsoft.CSharp.CSharpCodeProvider())
{
    var res = foo.CompileAssemblyFromSource(
        new System.CodeDom.Compiler.CompilerParameters() 
        {  
            GenerateInMemory = true 
        }, 
        "public class FooClass { public string Execute() { return \"output!\";}}"
    );

    var type = res.CompiledAssembly.GetType("FooClass");

    var obj = Activator.CreateInstance(type);

    var output = type.GetMethod("Execute").Invoke(obj, new object[] { });
}

This compiles a simple class from the source code string included, then instantiates the class and reflectively invokes a function on it.

Answer 2

Here is an example of how to use System.Linq.Expressions to add to Tim's answer. Obviously it isn't the prettiest code but having it in this nice tree-like form makes development so easy.

private  Expression<IsWordChar> CreateIsWordCharExpression()
{
    var e = Expression.Parameter(typeof(int), "e");
    var c = Expression.Variable(typeof(char), "c");
    var returnLabel = Expression.Label(Expression.Label(typeof(bool)), _falseConstant);
    var lambda = Expression.Lambda<IsWordChar>(
        Expression.Block(
            new[] { c },
            Expression.IfThen(
                Expression.OrElse(
                    Expression.Equal(e, Expression.Constant(-1)),
                    Expression.Equal(e, _inputLengthVar)
                ),
                Expression.Return(returnLabel.Target, _falseConstant)
            ),
            Expression.Assign(c, Expression.MakeIndex(_str, _stringCharsPropertyInfo, new[] { e })),
            Expression.IfThenElse(
                Expression.OrElse(
                    Expression.OrElse(
                        Expression.OrElse(
                            Expression.AndAlso(
                                Expression.GreaterThanOrEqual(c, Expression.Constant('a')),
                                Expression.LessThanOrEqual(c, Expression.Constant('z'))
                            ),
                            Expression.AndAlso(
                                Expression.GreaterThanOrEqual(c, Expression.Constant('A')),
                                Expression.LessThanOrEqual(c, Expression.Constant('Z'))
                            )
                        ),
                        Expression.AndAlso(
                            Expression.GreaterThanOrEqual(c, Expression.Constant('0')),
                            Expression.LessThanOrEqual(c, Expression.Constant('1'))
                        )
                    ),
                    Expression.Equal(c, Expression.Constant('_'))
                ),
                Expression.Return(returnLabel.Target, _trueConstant),
                Expression.Return(returnLabel.Target, _falseConstant)
            ),
            returnLabel
        ),
        "IsWordChar",
        new[] { e }
    );
    return lambda;
}

Answer 3

It's possible. It's easy or hard, depending on how much and what kind of code you want to write.

• Compile one-line expressions: System.Linq.Expressions (straightforward but limited)
• Compile whole programs: System.Reflection.Emit (hard to debug, but not impossible)

Edit: Note that, prior to .NET 4.0, System.Linq.Expressions is limited to what you can fit on a single line of C#: that is, no if, while, variable assignment etc.

Answer 4

Yes, you can do this. It is very slow, but you can certainly do it. Look at the CodeDOM or the (new CSharpCodeProvider().CreateCompiler()) in .Net.

Answer 5

Look into System.CodeDom. It will do exactly what you are looking for.

Answer 6

In Mono you use CSharp.Evaluator. It works truly in memory v. some of the other solutions mentioned that write out and read back in a file under the hood.

Answer 7

Also take a look at embedding a scripting language like Python, Ruby, Lua, etc.. all of those support executing code from memory without anything being written to the disk.

Answer 8

It's difficult, if not impossible to compile and execute C# without creating a file, because... Well, that's what compilation is- turning a language into an executable file. What you're looking for is some kind of scripting functionality. What you described in your question is essentially the difference between an interpreted language and a compiled language. See Wikipedia: Scripting language.

Depending on what you'll be using this feature for, you could make great use of a scripting language like Python, Ruby, or Lua. Here's an example: How do I run a Python script from C#?

This would make your application dependant upon python.exe (or whatever executable you'd need to run the scripting language you choose). If you want to avoid that, it might not be too hard to make your own scripting language that your application does the runtime for, depending on what you need to do with your injected script.

Edit: That first paragraph is rubbish. Sorry. See http://msdn.microsoft.com/en-us/library/8ffc3x75%28v=vs.110%29.aspx