CSharp-CodeDOM生成类

CodeDOM:代码文档对象模型。

参考：动态源代码生成和编译

.NET Framework 包括一个名为代码文档对象模型 (CodeDOM) 的机制。通过该机制，发出源代码的程序开发者可基于一种表示要呈现的代码的单一模型，在运行时以多种编程语言生成源代码。
为表示源代码，CodeDOM 元素相互链接，构成一个名为 CodeDOM 图的数据结构。该数据结构对某些源代码的结构建模。

System.CodeDom 命名空间定义某些类型，这些类型可以表示源代码的逻辑结构，且不依赖特定编程语言。 System.CodeDom.Compiler 命名空间定义某些类型，用于从 CodeDOM 图中生成源代码，并管理使用支持语言的源代码的编译工作。 编译器供应商或开发人员可以扩展支持语言。

.NET Framework 包括适用于 CSharpCodeProvider、JScriptCodeProvider 和 VBCodeProvider 的代码生成器和代码编译器。

使用CodeDOM创建类

CodeDOM 提供表示多种常见源代码元素的类型。 可以设计一个程序，它使用 CodeDOM 元素生成源代码模型来组合对象图。 对于支持的编程语言，可使用 CodeDOM 代码生成器将此对象图呈现为源代码。 还可使用 CodeDOM 将源代码编译为二进制程序集。

CodeDOM 的常见用途包括：

• 模板化代码生成：生成适用于 ASP.NET、XML Web 服务客户端代理、代码向导、设计器或其他代码发出机制的代码。
• 动态编译：支持一种或多种语言的代码编译。

参考：使用 CodeDom

System.CodeDom 命名空间提供用于表示源代码逻辑结构的类，独立于语言语法。

CodeDOM 图的结构类似于一个容器树。 每个可编译 CodeDOM 图的顶端容器或根部容器是 CodeCompileUnit。 源代码模型中的每个元素都必须通过图中 CodeObject 的属性链接至该图。

CodeDOM 定义名为 CodeCompileUnit 的对象，可引用 CodeDOM 对象图，该对象图塑造要编译的源代码的模型。 CodeCompileUnit 具有属性可用于存储对特性、命名空间和程序集的引用。

派生自 CodeDomProvider 类的 CodeDom 提供程序包含处理 CodeCompileUnit 所引用的对象图的方法。

详细请参考：如何：使用 CodeDOM 创建类

CodeStatement Class

namespace ConsoleApp1
{
    using System;
    using System.CodeDom;
    using System.CodeDom.Compiler;
    using System.IO;
    using System.Reflection;

    /// <summary>
    /// This code example creates a graph using a CodeCompileUnit and
    /// generates source code for the graph using the CSharpCodeProvider.
    /// </summary>
    internal class Sample
    {
        /// <summary>
        /// Define the compile unit to use for code generation.
        /// </summary>
        private CodeCompileUnit targetUnit;

        /// <summary>
        /// The only class in the compile unit. This class contains 2 fields,
        /// 3 properties, a constructor, an entry point, and 1 simple method.
        /// </summary>
        private CodeTypeDeclaration targetClass;

        /// <summary>
        /// The name of the file to contain the source code.
        /// </summary>
        private const string outputFileName = "SampleCode.cs";

        /// <summary>
        /// Define the class.
        /// </summary>
        public Sample()
        {
            // 创建编译单元
            targetUnit = new CodeCompileUnit();

            // 定义命名空间
            CodeNamespace samples = new CodeNamespace("CodeDOMSample");

            // 导入命名空间
            samples.Imports.Add(new CodeNamespaceImport("System"));

            // 定义类型
            targetClass = new CodeTypeDeclaration("CodeDOMCreatedClass");
            targetClass.IsClass = true;
            targetClass.TypeAttributes =
                TypeAttributes.Public | TypeAttributes.Sealed;

            // 向命名空间添加类型
            samples.Types.Add(targetClass);

            // 将代码元素链接至对象图
            targetUnit.Namespaces.Add(samples);
        }

        /// <summary>
        /// Adds two fields to the class.
        /// </summary>
        public void AddFields()
        {
            // Declare the widthValue field.
            CodeMemberField widthValueField = new CodeMemberField();
            widthValueField.Attributes = MemberAttributes.Private;
            widthValueField.Name = "widthValue";
            widthValueField.Type = new CodeTypeReference(typeof(System.Double));
            widthValueField.Comments.Add(new CodeCommentStatement(
                "The width of the object."));
            targetClass.Members.Add(widthValueField);

            // Declare the heightValue field
            CodeMemberField heightValueField = new CodeMemberField();
            heightValueField.Attributes = MemberAttributes.Private;
            heightValueField.Name = "heightValue";
            heightValueField.Type =
                new CodeTypeReference(typeof(System.Double));
            heightValueField.Comments.Add(new CodeCommentStatement(
                "The height of the object."));
            targetClass.Members.Add(heightValueField);
        }

        /// <summary>
        /// Add three properties to the class.
        /// </summary>
        public void AddProperties()
        {
            // Declare the read-only Width property.
            CodeMemberProperty widthProperty = new CodeMemberProperty();
            widthProperty.Attributes =
                MemberAttributes.Public | MemberAttributes.Final;
            widthProperty.Name = "Width";
            widthProperty.HasGet = true;
            widthProperty.Type = new CodeTypeReference(typeof(System.Double));
            widthProperty.Comments.Add(new CodeCommentStatement(
                "The Width property for the object."));
            widthProperty.GetStatements.Add(new CodeMethodReturnStatement(
                new CodeFieldReferenceExpression(
                new CodeThisReferenceExpression(), "widthValue")));
            targetClass.Members.Add(widthProperty);

            // Declare the read-only Height property.
            CodeMemberProperty heightProperty = new CodeMemberProperty();
            heightProperty.Attributes =
                MemberAttributes.Public | MemberAttributes.Final;
            heightProperty.Name = "Height";
            heightProperty.HasGet = true;
            heightProperty.Type = new CodeTypeReference(typeof(System.Double));
            heightProperty.Comments.Add(new CodeCommentStatement(
                "The Height property for the object."));
            heightProperty.GetStatements.Add(new CodeMethodReturnStatement(
                new CodeFieldReferenceExpression(
                new CodeThisReferenceExpression(), "heightValue")));
            targetClass.Members.Add(heightProperty);

            // Declare the read only Area property.
            CodeMemberProperty areaProperty = new CodeMemberProperty();
            areaProperty.Attributes =
                MemberAttributes.Public | MemberAttributes.Final;
            areaProperty.Name = "Area";
            areaProperty.HasGet = true;
            areaProperty.Type = new CodeTypeReference(typeof(System.Double));
            areaProperty.Comments.Add(new CodeCommentStatement(
                "The Area property for the object."));

            // Create an expression to calculate the area for the get accessor
            // of the Area property.
            CodeBinaryOperatorExpression areaExpression =
                new CodeBinaryOperatorExpression(
                new CodeFieldReferenceExpression(
                new CodeThisReferenceExpression(), "widthValue"),
                CodeBinaryOperatorType.Multiply,
                new CodeFieldReferenceExpression(
                new CodeThisReferenceExpression(), "heightValue"));
            areaProperty.GetStatements.Add(
                new CodeMethodReturnStatement(areaExpression));
            targetClass.Members.Add(areaProperty);
        }

        /// <summary>
        /// Adds a method to the class. This method multiplies values stored
        /// in both fields.
        /// </summary>
        public void AddMethod()
        {
            // Declaring a ToString method
            CodeMemberMethod toStringMethod = new CodeMemberMethod();
            toStringMethod.Attributes =
                MemberAttributes.Public | MemberAttributes.Override;
            toStringMethod.Name = "ToString";
            toStringMethod.ReturnType =
                new CodeTypeReference(typeof(System.String));

            CodeFieldReferenceExpression widthReference =
                new CodeFieldReferenceExpression(
                new CodeThisReferenceExpression(), "Width");
            CodeFieldReferenceExpression heightReference =
                new CodeFieldReferenceExpression(
                new CodeThisReferenceExpression(), "Height");
            CodeFieldReferenceExpression areaReference =
                new CodeFieldReferenceExpression(
                new CodeThisReferenceExpression(), "Area");

            // Declaring a return statement for method ToString.
            CodeMethodReturnStatement returnStatement =
                new CodeMethodReturnStatement();

            // This statement returns a string representation of the width,
            // height, and area.
            string formattedOutput = "The object:" + Environment.NewLine +
                " width = {0}," + Environment.NewLine +
                " height = {1}," + Environment.NewLine +
                " area = {2}";
            returnStatement.Expression =
                new CodeMethodInvokeExpression(
                new CodeTypeReferenceExpression("System.String"), "Format",
                new CodePrimitiveExpression(formattedOutput),
                widthReference, heightReference, areaReference);
            toStringMethod.Statements.Add(returnStatement);
            targetClass.Members.Add(toStringMethod);
        }

        /// <summary>
        /// Add a constructor to the class.
        /// </summary>
        public void AddConstructor()
        {
            // Declare the constructor
            CodeConstructor constructor = new CodeConstructor();
            constructor.Attributes =
                MemberAttributes.Public | MemberAttributes.Final;

            // Add parameters.
            constructor.Parameters.Add(new CodeParameterDeclarationExpression(
                typeof(System.Double), "width"));
            constructor.Parameters.Add(new CodeParameterDeclarationExpression(
                typeof(System.Double), "height"));

            // Add field initialization logic
            CodeFieldReferenceExpression widthReference =
                new CodeFieldReferenceExpression(
                new CodeThisReferenceExpression(), "widthValue");
            constructor.Statements.Add(new CodeAssignStatement(widthReference,
                new CodeArgumentReferenceExpression("width")));
            CodeFieldReferenceExpression heightReference =
                new CodeFieldReferenceExpression(
                new CodeThisReferenceExpression(), "heightValue");
            constructor.Statements.Add(new CodeAssignStatement(heightReference,
                new CodeArgumentReferenceExpression("height")));
            targetClass.Members.Add(constructor);
        }

        /// <summary>
        /// Add an entry point to the class.
        /// </summary>
        public void AddEntryPoint()
        {
            // 为可执行程序定义代码入口点方法
            CodeEntryPointMethod start = new CodeEntryPointMethod();
            CodeObjectCreateExpression objectCreate =
                new CodeObjectCreateExpression(
                new CodeTypeReference("CodeDOMCreatedClass"),
                new CodePrimitiveExpression(5.3),
                new CodePrimitiveExpression(6.9));

            // Add the statement:
            // "CodeDOMCreatedClass testClass =
            //     new CodeDOMCreatedClass(5.3, 6.9);"
            start.Statements.Add(new CodeVariableDeclarationStatement(
                new CodeTypeReference("CodeDOMCreatedClass"), "testClass",
                objectCreate));

            // Creat the expression:
            // "testClass.ToString()"
            CodeMethodInvokeExpression toStringInvoke =
                new CodeMethodInvokeExpression(
                new CodeVariableReferenceExpression("testClass"), "ToString");

            // Add a System.Console.WriteLine statement with the previous
            // expression as a parameter.
            start.Statements.Add(new CodeMethodInvokeExpression(
                new CodeTypeReferenceExpression("System.Console"),
                "WriteLine", toStringInvoke));
            targetClass.Members.Add(start);
        }

        /// <summary>
        /// Generate CSharp source code from the compile unit.
        /// </summary>
        /// <param name="filename">Output file name</param>
        public void GenerateCSharpCode(string fileName)
        {
            CodeDomProvider provider = CodeDomProvider.CreateProvider("CSharp");
            CodeGeneratorOptions options = new CodeGeneratorOptions();
            options.BracingStyle = "C";
            using (StreamWriter sourceWriter = new StreamWriter(fileName))
            {
                provider.GenerateCodeFromCompileUnit(
                    targetUnit, sourceWriter, options);
            }
        }

        /// <summary>
        /// Create the CodeDOM graph and generate the code.
        /// </summary>
        private static void Main()
        {
            Sample sample = new Sample();
            sample.AddFields();
            sample.AddProperties();
            sample.AddMethod();
            sample.AddConstructor();
            sample.AddEntryPoint();
            sample.GenerateCSharpCode(outputFileName);
        }
    }
}

生成类的代码：

//------------------------------------------------------------------------------
// <auto-generated>
//     此代码由工具生成。
//     运行时版本:4.0.30319.42000
//
//     对此文件的更改可能会导致不正确的行为，并且如果
//     重新生成代码，这些更改将会丢失。
// </auto-generated>
//------------------------------------------------------------------------------

namespace CodeDOMSample
{
    using System;


    public sealed class CodeDOMCreatedClass
    {

        // The width of the object.
        private double widthValue;

        // The height of the object.
        private double heightValue;

        public CodeDOMCreatedClass(double width, double height)
        {
            this.widthValue = width;
            this.heightValue = height;
        }

        // The Width property for the object.
        public double Width
        {
            get
            {
                return this.widthValue;
            }
        }

        // The Height property for the object.
        public double Height
        {
            get
            {
                return this.heightValue;
            }
        }

        // The Area property for the object.
        public double Area
        {
            get
            {
                return (this.widthValue * this.heightValue);
            }
        }

        public override string ToString()
        {
            return string.Format("The object:\r\n width = {0},\r\n height = {1},\r\n area = {2}", this.Width, this.Height, this.Area);
        }

        public static void Main()
        {
            CodeDOMCreatedClass testClass = new CodeDOMCreatedClass(5.3D, 6.9D);
            System.Console.WriteLine(testClass.ToString());
        }
    }
}