使用CodeDom来生成.cs文件

在学使用CodeDom来动态生成.cs文件，使用帮助里的例子，代码居然编译不通过
自己修改，调试通过，整理后主要代码如下：

命名空间：
using System.CodeDom;
using System.CodeDom.Compiler;
using Microsoft.CSharp;
using System.IO;

  private void button1_Click(object sender, System.EventArgs e)
  {
   CodeCompileUnit CompileUnit = new CodeCompileUnit();
   CodeNamespace Samples = new CodeNamespace("Samples");
   Samples.Imports.Add( new CodeNamespaceImport("System") );
   CompileUnit.Namespaces.Add( Samples );
   CodeTypeDeclaration Class1 = new CodeTypeDeclaration("Class1");
   Samples.Types.Add(Class1);

   CodeEntryPointMethod Start = new CodeEntryPointMethod();
   
   //输出HelloWord
   CodeMethodInvokeExpression cs1 = new CodeMethodInvokeExpression( new
    CodeTypeReferenceExpression("System.Console"), "WriteLine", new
    CodePrimitiveExpression("Hello World!") );
   
   Start.Statements.Add(cs1);
   

   Class1.Members.Add( Start );
   //CSharpCodeProvider provider = new CSharpCodeProvider();
   //ICodeGenerator gen = provider.CreateGenerator();
   GenerateGraph(CompileUnit);

  }
  public void GenerateGraph(CodeCompileUnit compileunit)
  {
   // Obtains an ICodeGenerator from a CodeDomProvider class.
   CSharpCodeProvider provider = new CSharpCodeProvider();
   ICodeGenerator gen = provider.CreateGenerator();
  
   // Creates a StreamWriter to an output file.
   StreamWriter sw = new StreamWriter("d:\\TestGraph.cs", false);

   // Generates source code using the code generator.
   gen.GenerateCodeFromCompileUnit(compileunit, sw, new    CodeGeneratorOptions());
  
   // Closes the output files.
   sw.Close();
  }

  private void button2_Click(object sender, System.EventArgs e)
  {
   CompileCode("d:\\TestGraph.cs");
  }
  //编辑生成Exe
  public CompilerResults CompileCode(string filepath)
  {
   // Obtains an ICodeCompiler from a CodeDomProvider class.
   CSharpCodeProvider provider = new CSharpCodeProvider();
   ICodeCompiler compiler = provider.CreateCompiler();

   // Configures a compiler parameters object which links System.dll and
   // generates a file name based on the specified source file name.
   CompilerParameters cp = new CompilerParameters(new string[] {"System.dll"}, filepath.Substring(0, filepath.LastIndexOf(".")+1)+"exe", false);

   // Indicates that an executable rather than a .dll should be generated.
   cp.GenerateExecutable = true;

   // Invokes compilation.
   CompilerResults cr = compiler.CompileAssemblyFromFile(cp, filepath);  

   // Returns the results of compilation.
   return cr;       
  }

帮助里的例子在：
.NET Framework->使用 .NET Framework 编程->动态生成和编译以多种语言表示的源代码