Is it possible to dynamically compile and execute C code fragments

Question

I was wondering if it is possible to save C  code fragments to a text file  or any input stream   and then execute those dynamically  Assuming what is provided to me would compile fine within any Main   block  is it possible to compile and or execute this code  I would prefer to compile it for performance reasons   At the very least  I could define an interface that they would be required to implement  then they would provide a code  section  that implemented that interface

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To compile you could just initiate a shell call to the csc compiler. You may have a headache trying to keep your paths and switches straight but it certainly can be done.

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EDIT: Or better yet, use the CodeDOM as Noldorin suggested...

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You can compile a piece C  of code into memory and generate assembly bytes with Roslyn  It s already mentioned but would be worth adding some Roslyn example for this here  The following is the complete example   using System  using System Collections Generic  using System IO  using System Linq  using System Reflection  using Microsoft CodeAnalysis  using Microsoft CodeAnalysis CSharp  using Microsoft CodeAnalysis Emit   namespace RoslynCompileSample       class Program               static void Main string   args                           define source code  then parse it  to the type used for compilation              SyntaxTree syntaxTree   CSharpSyntaxTree ParseText                    using System                   namespace RoslynCompileSample                                       public class Writer                                               public void Write string message                                                        Console WriteLine message                                                                                        define other necessary objects for compilation             string assemblyName   Path GetRandomFileName                MetadataReference   references   new MetadataReference                                 MetadataReference CreateFromFile typeof object  Assembly Location                   MetadataReference CreateFromFile typeof Enumerable  Assembly Location                                 analyse and generate IL code from syntax tree             CSharpCompilation compilation   CSharpCompilation Create                  assemblyName                  syntaxTrees  new     syntaxTree                    references  references                  options  new CSharpCompilationOptions OutputKind DynamicallyLinkedLibrary                 using  var ms   new MemoryStream                                     write IL code into memory                 EmitResult result   compilation Emit ms                    if   result Success                                           handle exceptions                     IEnumerable lt Diagnostic gt  failures   result Diagnostics Where diagnostic   gt                           diagnostic IsWarningAsError                             diagnostic Severity    DiagnosticSeverity Error                        foreach  Diagnostic diagnostic in failures                                                Console Error WriteLine   0    1    diagnostic Id  diagnostic GetMessage                                                             else                                          load this  virtual  DLL so that we can use                     ms Seek 0  SeekOrigin Begin                       Assembly assembly   Assembly Load ms ToArray                             create instance of the desired class and call the desired function                     Type type   assembly GetType  RoslynCompileSample Writer                        object obj   Activator CreateInstance type                       type InvokeMember  Write                           BindingFlags Default   BindingFlags InvokeMethod                          null                          obj                          new object      Hello World                                                   Console ReadLine

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Others have already given good answers on how to generate code at runtime so I thought I would address your second paragraph   I have some experience with this and just want to share a lesson I learned from that experience      At the very least  I could define an   interface that they would be required   to implement  then they would provide   a code  section  that implemented that   interface    You may have a problem if you use an interface as a base type  If you add a single new method to the interface in the future all existing client-supplied classes that implement the interface now become abstract  meaning you won t be able to compile or instantiate the client-supplied class at runtime   I had this issue when it came time to add a new method after about 1 year of shipping the old interface and after distributing a large amount of  legacy  data that needed to be supported   I ended up making a new interface that inherited from the old one but this approach made it harder to load and instantiate the client-supplied classes because I had to check which interface was available   One solution I thought of at the time was to instead use an actual class as a base type such as the one below   The class itself can be marked abstract but all methods should be empty virtual methods  not abstract methods    Clients can then override the methods they want and I can add new methods to the base class without invalidating existing client-supplied code   public abstract class BaseClass       public virtual void Foo1           public virtual bool Foo2     return false                Regardless of whether this problem applies you should consider how to version the interface between your code base and the client-supplied code

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Found this useful - ensures the compiled Assembly references everything you currently have referenced  since there s a good chance you wanted the C  you re compiling to use some classes etc in the code that s emitting this   string code is the dynamic C  being compiled          var refs   AppDomain CurrentDomain GetAssemblies            var refFiles   refs Where a   gt   a IsDynamic  Select a   gt  a Location  ToArray            var cSharp    new Microsoft CSharp CSharpCodeProvider    CreateCompiler            var compileParams   new System CodeDom Compiler CompilerParameters refFiles           compileParams GenerateInMemory   true          compileParams GenerateExecutable   false           var compilerResult   cSharp CompileAssemblyFromSource compileParams  code           var asm   compilerResult CompiledAssembly   In my case I was emitting a class  whose name was stored in a string  className  which had a single public static method named Get    that returned with type StoryDataIds  Here s what calling that method looks like          var tempType   asm GetType className           var ids    StoryDataIds tempType GetMethod  quot Get quot   Invoke null  null    Warning  Compilation can be surprisingly  extremely slow  A small  relatively simple 10-line chunk of code compiles at normal priority in 2-10 seconds on our relatively fast server  You should never tie calls to CompileAssemblyFromSource   to anything with normal performance expectations  like a web request  Instead  proactively compile code you need on a low-priority thread and have a way of dealing with code that requires that code to be ready  until it s had a chance to finish compiling  For example you could use it in a batch job process

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I recently needed to spawn processes for unit testing  This post was useful as I created a simple class to do that with either code as a string or code from my project  To build this class  you ll need the ICSharpCode Decompiler and Microsoft CodeAnalysis NuGet packages  Here s the class   using ICSharpCode Decompiler  using ICSharpCode Decompiler CSharp  using ICSharpCode Decompiler TypeSystem  using Microsoft CodeAnalysis  using Microsoft CodeAnalysis CSharp  using System  using System Collections Generic  using System IO  using System Linq  using System Reflection   public static class CSharpRunner      public static object Run string snippet  IEnumerable lt Assembly gt  references  string typeName  string methodName  params object   args    gt        Invoke Compile Parse snippet   references   typeName  methodName  args       public static object Run MethodInfo methodInfo  params object   args             var refs   methodInfo DeclaringType Assembly GetReferencedAssemblies   Select n   gt  Assembly Load n          return Invoke Compile Decompile methodInfo   refs   methodInfo DeclaringType FullName  methodInfo Name  args            private static Assembly Compile SyntaxTree syntaxTree  IEnumerable lt Assembly gt  references   null             if  references is null  references   new     typeof object  Assembly  typeof Enumerable  Assembly          var mrefs   references Select a   gt  MetadataReference CreateFromFile a Location          var compilation   CSharpCompilation Create Path GetRandomFileName    new     syntaxTree    mrefs  new CSharpCompilationOptions OutputKind DynamicallyLinkedLibrary           using  var ms   new MemoryStream                     var result   compilation Emit ms            if  result Success                         ms Seek 0  SeekOrigin Begin               return Assembly Load ms ToArray                         else                        throw new InvalidOperationException string Join   n   result Diagnostics Where diagnostic   gt  diagnostic IsWarningAsError    diagnostic Severity    DiagnosticSeverity Error  Select d   gt     d Id    d GetMessage                                     private static SyntaxTree Decompile MethodInfo methodInfo             var decompiler   new CSharpDecompiler methodInfo DeclaringType Assembly Location  new DecompilerSettings           var typeInfo   decompiler TypeSystem MainModule Compilation FindType methodInfo DeclaringType  GetDefinition          return Parse decompiler DecompileTypeAsString typeInfo FullTypeName             private static object Invoke Assembly assembly  string typeName  string methodName  object   args             var type   assembly GetType typeName         var obj   Activator CreateInstance type         return type InvokeMember methodName  BindingFlags Default   BindingFlags InvokeMethod  null  obj  args            private static SyntaxTree Parse string snippet    gt  CSharpSyntaxTree ParseText snippet       To use it  call the Run methods as below   void Demo1        const string code         public class Runner            public void Run     System IO File AppendAllText    C  Temp NUnitTest txt    System DateTime Now ToString   o         n                  CSharpRunner Run code  null   Runner    Run       void Demo2        CSharpRunner Run typeof Runner  GetMethod  Run        public class Runner      public void Run     System IO File AppendAllText   C  Temp NUnitTest txt   System DateTime Now ToString  o       n

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The best solution in C  all static  NET languages is to use the CodeDOM for such things   As a note  its other main purpose is for dynamically constructing bits of code  or even whole classes    Here s a nice short example take from LukeH s blog  which uses some LINQ too just for fun   using System  using System Collections Generic  using System Linq  using Microsoft CSharp  using System CodeDom Compiler   class Program       static void Main string   args                var csc   new CSharpCodeProvider new Dictionary lt string  string gt         CompilerVersion    v3 5                var parameters   new CompilerParameters new      mscorlib dll    System Core dll      foo exe   true           parameters GenerateExecutable   true          CompilerResults results   csc CompileAssemblyFromSource parameters            using System Linq              class Program                 public static void Main string   args                    var q   from i in Enumerable Range 1 100                            where i   2    0                           select i                                           results Errors Cast lt CompilerError gt    ToList   ForEach error   gt  Console WriteLine error ErrorText              The class of primary importance here is the CSharpCodeProvider which utilises the compiler to compile code on the fly  If you want to then run the code  you just need to use a bit of reflection to dynamically load the assembly and execute it   Here is another example in C  that  although slightly less concise  additionally shows you precisely how to run the runtime-compiled code using the System Reflection namespace

[c#] Is it possible to dynamically compile and execute C# code fragments?

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