What is CodeDom

The "CodeDom" is an object model that represents actually a source code. It is designed for language independent - once you create a "CodeDom" hierarchy for a program we can then generate the source code in any .NET language. So let's try to do some real practical and simple to just get a feel of how powerful "CodeDom" is.

We will try to generate the following code shown below. The below code which will be generated does not do any special thing by just displays a hello message and waits for the key to be clicked.

namespace InterviewQuestions

{

using System;

public class EntryPoint

{

public static void Main()

{

System.Console.WriteLine("Hello from Interview Question series");

System.Console.ReadLine();

}

}

}

The "Codedom" folder at the CD has one "GenerateCode" method that returns "CodeCompileUnit" object. The "CodeDom" is nothing but a full DOM model where every object in the structure shows a code unit. I have put some comments on the code so that the code is self understandable. I have put some comment at the code below so that readers can follow what is exactly happening. When you click the button it generates the "MyCode.cs" and also compiles the "Mycode.exe" in the "bin" folder.

private CodeCompileUnit GenerateCode()

{

// Definition of the Main method which will be entry point

CodeEntryPointMethod objMainMethod = new CodeEntryPointMethod();

objMainMethod.Name = "Main";

// generate this expression: Console

CodeTypeReferenceExpression consoleType = new CodeTypeReferenceExpression();

consoleType.Type = new CodeTypeReference(typeof(Console));

// Set up the argument list to pass to Console.WriteLine()

CodeExpression[] writeLineArgs = new CodeExpression[1];

CodePrimitiveExpression arg0 = new CodePrimitiveExpression("Hello from Interview

Question series");

writeLineArgs[0] = arg0;

// generate this statement: Console.WriteLine(message)

CodeMethodReferenceExpression writeLineRef = new

CodeMethodReferenceExpression(consoleType, "WriteLine");

CodeMethodInvokeExpression writeLine = new

CodeMethodInvokeExpression(writeLineRef, writeLineArgs);

// generate this statement: Console.ReadLine()

CodeMethodReferenceExpression readLineRef = new

CodeMethodReferenceExpression(consoleType, "ReadLine");

CodeMethodInvokeExpression readLine = new

CodeMethodInvokeExpression(readLineRef);

// Add Main() method to a class

CodeTypeDeclaration theClass = new CodeTypeDeclaration();

theClass.Members.Add(objMainMethod);

theClass.Name = "EntryPoint";

// Add both the code of WriteLine and Readline

objMainMethod.Statements.Add(writeLine);

objMainMethod.Statements.Add(readLine);

// Add namespace and add class

CodeNamespace ns = new CodeNamespace("InterviewQuestions");

ns.Imports.Add(new CodeNamespaceImport("System"));

ns.Types.Add(theClass);

// Generate the Compile Unit

CodeCompileUnit unit = new CodeCompileUnit();

unit.Namespaces.Add(ns);