将DataTable对象转换为Recordset对象

将DataTable对象转换为Recordset对象

在.net中用ADO.NET取代了ADO实现对数据的访问，但一些COM控件只支持ADO并不支持ADO.NET。为了使用这类控件，只能将ADO.NET中的数据对象，比如DataTable为ADO中的Recordset（DataSet对象本质上是DataTable的集合，因此本文只讲述DataTable对象的转换）。
思路
1.         创建Recordset对象后，在其中对应DataTable的Column创建Field，为此需要将ADO.NET的数据类型转换为ADO的数据类型；
2.         打开Recordset对象，对应DataTable对象中的每一行，在Recordset对象中新建一条记录，并对每个字段赋值。
using System;
using System.Collections.Generic;
using System.Text;
using System.Data;
using System.Data.SqlClient;
using ADODB;
using System.Text.RegularExpressions;
using System.Reflection;

namespace OWC
{
    public class DBA
    {
        SqlConnection conn;
        SqlDataAdapter da;
        SqlCommand comm;
        DataTable dt = new DataTable();
        string connStr = "server=localhost;database=Cases20061227;uid=sa;pwd=sa;";
        string selStr = "select * from TABLE1";
        public DataTable getdata()
        {
            conn = new SqlConnection(connStr);
            da = new SqlDataAdapter(selStr,conn);
            da.Fill(dt);
            return dt;
        }
        public Recordset GetRecordset()
        {
            ADODB.ConnectionClass connADO = new ConnectionClass();
            ADODB.RecordsetClass recordADO = new RecordsetClass();
            string connStr = "driver={sql server};server=localhost;uid=sa;pwd=sa; database=Cases20061227";
            connADO.Open(connStr, "", "", -1);
            recordADO.ActiveConnection = connADO;
            recordADO.CursorType = ADODB.CursorTypeEnum.adOpenStatic;
            recordADO.CursorLocation = ADODB.CursorLocationEnum.adUseClient;
            string strSQL = "select * from TABLE1";
            recordADO.Open(strSQL, connADO, ADODB.CursorTypeEnum.adOpenStatic, ADODB.LockTypeEnum.adLockBatchOptimistic, 1);

            return recordADO;
        }
        //Missing的命名空间using System.Reflection;
        public Recordset ConvertDataTableToRecordset(DataTable table)
        {
             Recordset rs=new RecordsetClass();
             foreach(DataColumn dc in table.Columns)
             {
                rs.Fields._Append(dc.ColumnName, GetDataType(dc.DataType), -1, FieldAttributeEnum.adFldIsNullable);
             }
              rs.Open(Missing.Value, Missing.Value, CursorTypeEnum.adOpenUnspecified, LockTypeEnum.adLockUnspecified, -1);
              foreach(DataRow dr in table.Rows)
              {
                    rs.AddNew(Missing.Value, Missing.Value);object o;
                    for(int i=0; i<table.Columns.Count; i++)
                    {
                           rs.Fields[i].Value=dr[i];
                           o=rs.Fields[i].Value;
                    }
              }
              return rs;
        }
        public static DataTypeEnum GetDataType(Type dataType)
        {
            switch (dataType.ToString())
            {
                case "System.Boolean": return DataTypeEnum.adBoolean;
                case "System.Byte": return DataTypeEnum.adUnsignedTinyInt;
                case "System.Char": return DataTypeEnum.adChar;
                case "System.DateTime": return DataTypeEnum.adDate;
                case "System.Decimal": return DataTypeEnum.adDecimal;
                case "System.Double": return DataTypeEnum.adDouble;
                case "System.Int16": return DataTypeEnum.adSmallInt;
                case "System.Int32": return DataTypeEnum.adInteger;
                case "System.Int64": return DataTypeEnum.adBigInt;
                case "System.SByte": return DataTypeEnum.adTinyInt;
                case "System.Single": return DataTypeEnum.adSingle;
                case "System.String": return DataTypeEnum.adVarChar;
                case "System.UInt16": return DataTypeEnum.adUnsignedSmallInt;
                case "System.UInt32": return DataTypeEnum.adUnsignedInt;
                case "System.UInt64": return DataTypeEnum.adUnsignedBigInt;
                default: throw new Exception("没有对应的数据类型");
            }
        }
    }
}
说明：
1.         需要添加ADODB库的引用，该库位于COM页，名称为“Microsoft ActiveX Data Objects 2.0 Library”；
2.         C#语法中没有默认参数，只能使用System.Reflection.Missing的Value属性，但该属性只能用于引用类型，而不能用于枚举、整型等值类型。