Question Can I execute C# code in C#?

csharp

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Can I execute C# code in C#? I've the variable:
C#:
string csharpCode = @"
using System;
class Program {
           static void Main() {
                        Console.WriteLine(""Hello world"");
           }
}

"

and I want execute it, is there a function for do this?
 
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Skydiver

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You can use the CodeDOM to compile from source to get an assembly, then load and execute the assembly.

I highly, highly recommend not doing this if you don't trust the the code that is given to you to compile and run. What happens if the code given to you to compile and run was:
C#:
class Program
{
    static void Main()
    {
        Directory.Delete(@"C:\", true);
    }
}
 

csharp

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I've already tried to use System.Reflection.Assembly but if I compile the code in a single file and run it with System.Reflection.Assembly doesn't work
 

Skydiver

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What errors are you getting? If you aren't getting any errors, what behavior are you seeing. What behavior were you expecting to see?

How exactly are you using System.Reflection.Assembly to load an assembly and execute it?
 

csharp

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Thanks for yours replies, I've a C# project that contained more files and your pseudo code is:
First file:
C#:
using System;
namespace ConsoleApp1 {
    class Program {
        static void Main(string[] args) {
              Console.WriteLine("enter a number: ");
              int number=Convert.ToInt32(Console.ReadLine());
              numbers.cheque(number);
        }
    }
}

Second file:
C#:
using System;
namespace ConsoleApp1 {
    class numbers {
        public void cheque(int number) {
              if (number > 10) Console.WriteLine("{0} is > of 10", number);
        }
    }
}

and I compile them in a single file and for run them I do:

C#:
var assembly=Assembly.Load(File.ReadAllBytes("path/to/file"));
var param=new object[1] { string.Empty };
assembly.EntryPoint.Invoke(null, param);

The exception is invalid CIL image
 
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Skydiver

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In the future, please use CODE tags when you have multiple lines of code. Onlly use ICODE (inlike code) tags for single line code. The CODE tags button on the toolbar looks like "</>", while the ICODE tags look like ">_" . Yes, I know it looks confusing because the standard MarkDown iconography for code sections is ">_".
 

Skydiver

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What exactly is the exception type? I assume that "invalid CIL image" is the exception message. Which line is throwing that exception?

Why are you using Assembly.Load(File.ReadAllBytes("path/to/file")) instead of much simpler Assembly.LoadFile("path/to/file") ?
 

csharp

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Maybe the only one way is put the C# source in a variable and after I should execute the code contained in the variable but how can I execute the code contained in a variable? or is there another way for compile a C# project in a single file?
 

Skydiver

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The following worked for me.
In a project SimpleCS.proj, I've got
SimpleCS.cs:
using System;

namespace SimpleCS
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("I'm running!");
            Console.WriteLine(string.Join(" ", args));
        }
    }
}

which gets compiled into "D:\z\test\SimpleCS\SimpleCS\bin\debug\SimpleCS.exe".

In my test program (SimpleCSCore) I have:
Progam.cs:
using System.Reflection;

class Program
{
    static void Main(string[] args)
    {
        var assembly = Assembly.LoadFile("d:/z/test/SimpleCS/SimpleCS/bin/debug/SimpleCS.exe");
        assembly.EntryPoint.Invoke(null, new [] { args });
    }
}

When I compile and run the test program, the output is correct:
Screenshot_1.png
 

Skydiver

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Maybe the only one way is put the C# source in a variable and after I should execute the code contained in the variable but how can I execute the code contained in a variable?
As I said in post #2, you would compile that into an assembly, load the assembly and execute it.
or is there another way for compile a C# project in a single file?
How are you currently compiling your C# project into a single file?
 

csharp

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Ok but for compile I go to publish and select option for compile all project (that contains more .cs files) in a single exe, maybe this is the error
 

Skydiver

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Hmmm. I've never tried that. I'm not sure if that single executable is even a CIL assembly file. I'll try that later today when I get back to my PC again.

Does that single executable run correctly?

Did you generate the executable to target the correct platform?
 

Skydiver

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I managed to reproduce the problem. It's because the generated file is not a .NET assembly. (Even ILDASM is not recognizing the executable as an assembly.)

Based on the single executable feature description, what happens is that executable unpacks itself into memory (or a temporary directory in the case of .NET Core 3.x), and then starts executing from there. Since Assembly.LoadFile() is expecting to find an .NET assembly, not an generic executable, it throws that BadImageExeception that you are seeing.
 
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Skydiver

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Yes. That's how the standard C# compiler works. Multiple source files get compiled into a single assembly.

The difference between the single executable described above and the standard compiled .NET assembly is that the former packs not just the main running assembly, but also all the dependent assemblies into a single file. The latter will only be an assembly that contains all the code that you compiled -- any dependent assemblies will either be in the same directory as the main executable or installed in the GAC.
 

csharp

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Sorry but I haven't understood how can I compile the project in a single file and execute it with System.Reflection.Assembly.LoadFile()?
 

Skydiver

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Right click on your project in the solution explorer. Select "Build". Visual Studio will compile all the .CS files in your project into a single assembly.
 

Skydiver

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If you don't even understand the fundamentals of how your basic developer tools works, why are you taking on this more complex problem? I would recommend stepping back and learning more about the language and the tools surrounding the language before embarking on reflection and executing other code.
 
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