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

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