Question

I want a method, annotation or something else that lets me treat a string as C# code.

I read about CodeDom, Reflection and T4 templates but that isn’t what I’m looking for.

What I need is more simple, I hope. I don´t want code generated at run-time.

Here’s an example to clarify what I want. I’m using VS2010, Entity Framework 5 and the Code First approach.

I have an Insert method for each entity type. The following is the code for the method to insert a Cliente (Costumer). If a Cliente exists in the database then its updated instead of inserted:

    public int InsertarCliente(Cliente cliente)
    {
        int id = cliente.ClienteId;

        try
        {
            if (id != -1)
            {
                var clt = db.Clientes.Find(id);
                clt.Nombre = cliente.Nombre;
                clt.Apellido1 = cliente.Apellido1;
                clt.Apellido2 = cliente.Apellido2;
                // more similar statements
            }
            else
                db.Clientes.Add(cliente);

            db.SaveChanges();
            return cliente.ClienteId;
        }
        catch (DbEntityValidationException exc)
        {
            // code
        }
    }

I was trying to use CodeDom to create a generic method that works for any entity type.
The method doesn’t work and I know why: CodeDom doesn’t compile and run arbitrary code, it requires extra namespaces, using statements, classes, methods, etc. That method doesn’t work, here is the code to clarify what I was trying to do:

    public int Insertar<TEntity>(TEntity entidad, string[] atributos)
            where TEntity : class
    {
        string nombreEntidad = entidad.GetType().Name;
        string entidadId = nombreEntidad + "Id";
        string tabla = nombreEntidad + "s";

        int id = Convert.ToInt32(
             entidad.GetType().GetProperty(entidadId).GetValue(entidad, null));

        try
        {
            CodeDomProvider codeProvider = CodeDomProvider.CreateProvider("CSharp");
            CompilerParameters cp = new CompilerParameters();
            cp.GenerateExecutable = false;
            cp.GenerateInMemory = true;
            CompilerResults cr;
            string codigo;

            if (id != -1)
            {
                codigo = "var entidadAlmacenada = db." + tabla + ".Find(id);";
                cr = codeProvider.CompileAssemblyFromSource(cp, codigo);
                CompilerResults cr2;
                string codigoActualizador;

                foreach (string atr in atributos)
                {
                    codigoActualizador =
                        "entidadAlmacenada." + atr + " = entidad." + atr + ";";
                    cr2 = codeProvider.CompileAssemblyFromSource(
                              cp, codigoActualizador);
                }                        
            }
            else
            {
                codigo = "db." + tabla + ".Add(entidad);";
                cr = codeProvider.CompileAssemblyFromSource(cp, codigo);
            }

            db.SaveChanges();
            return Convert.ToInt32(
                entidad.GetType().GetProperty(entidadId).GetValue(entidad, null));
        }
        catch (DbEntityValidationException exc)
        {
            // code
        }
    }

I want a way to convert (inline) a string that represents code to the code that it represents.

Something like:

    string code = "line of code";
    code.toCode(); // or
    toCode(code); // or
    [ToCode]
    code;

Sorry if I’m writing too much, but I want to be clear this time.

What I need is that a string “containing code” to be replaced by the code before compilation time. No run-time compilation or execution.

Is there a way to do something like that?

TIA

EDIT:

The above example was just an example. But I want the “string to code conversion” in any situation.

Answer 1

An alternative (and imho preferrable) approach to achieve what you are trying to do is using db.Set<TEntity>().Find(id) etc