ASP.NET 2.0 WebService中传递DataTable参考

　　在2.0正式版发布之前，就满天的看到关于DataTable支持序列化的新特性宣传，满以为从此以后使用DataTable就和DataSet一样方便了，结果在应用项目的时候才发现并非那么回事。
　　DataTable是支持序列化了，但是微软并没有把他做的特别方便，还需要我们自己来做一些工作之后才能够在WebService里面传递DataTable，否则在引用DataTable的时候会发现DataTable变成了一个什么Proxy类型。
　　首先编写类DataTableSchemaImporterExtension，代码如下：
using System;
using System.Collections.Generic;
using System.Text;
using System.Xml.Serialization.Advanced;
using System.Collections;
using System.Xml.Schema;
using System.Xml.Serialization;
using System.CodeDom;
using System.CodeDom.Compiler;
using System.Xml;
using System.Data;

namespace Xrinehart.Tools.WebService.SchemaImporter
{
    class DataTableSchemaImporterExtension : SchemaImporterExtension
    {

        // DataTableSchemaImporterExtension is used for WebServices, it is used to recognize the schema for DataTable within wsdl

        Hashtable importedTypes = new Hashtable();

        public override string ImportSchemaType(string name, string schemaNamespace, XmlSchemaObject context, XmlSchemas schemas, XmlSchemaImporter importer, CodeCompileUnit compileUnit, CodeNamespace mainNamespace, CodeGenerationOptions options, CodeDomProvider codeProvider)
        {

            IList values = schemas.GetSchemas(schemaNamespace);

            if (values.Count != 1)
            {

                return null;

            }

            XmlSchema schema = values[0] as XmlSchema;

            if (schema == null)

                return null;

            XmlSchemaType type = (XmlSchemaType)schema.SchemaTypes[new XmlQualifiedName(name, schemaNamespace)];

            return ImportSchemaType(type, context, schemas, importer, compileUnit, mainNamespace, options, codeProvider);

        }

        public override string ImportSchemaType(XmlSchemaType type, XmlSchemaObject context, XmlSchemas schemas, XmlSchemaImporter importer, CodeCompileUnit compileUnit, CodeNamespace mainNamespace, CodeGenerationOptions options, CodeDomProvider codeProvider)
        {

            if (type == null)
            {

                return null;

            }

            if (importedTypes[type] != null)
            {

                mainNamespace.Imports.Add(new CodeNamespaceImport(typeof(DataSet).Namespace));

                compileUnit.ReferencedAssemblies.Add("System.Data.dll");

                return (string)importedTypes[type];

            }

            if (!(context is XmlSchemaElement))

                return null;

            if (type is XmlSchemaComplexType)
            {

                XmlSchemaComplexType ct = (XmlSchemaComplexType)type;

                if (ct.Particle is XmlSchemaSequence)
                {

                    XmlSchemaObjectCollection items = ((XmlSchemaSequence)ct.Particle).Items;

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