关于DataAdapter填充非框架数据集DataSet

[Manonloki]

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;
using System.Data.Sql;
using System.Data.SqlClient;

namespace DataAdapterDemo
{
    public class SQLAccess
    {
        private static SqlConnection conn = new SqlConnection(@"server=.\SQLExpress;database=AdapterDemo;Trusted_Connection=SSPI");
        private SqlDataAdapter sda = new SqlDataAdapter();
        private DataSet ds = null;

        public DataSet getDataSet()
        {
            try
            {
                conn.Open();
                SqlCommand selectCommand = new SqlCommand("select * from Demo", conn);
               
                sda.SelectCommand = selectCommand;
                sda.Fill(ds);
                return ds;
            }
            catch
            {
                return null;
            }
            finally
            {
                conn.Close();
                conn.Dispose();
                sda.Dispose();
            }
        }
    }
}

代码如上 但是报错 "值不能为空。\r\n参数名: dataSet"

请问如何解决……

[一切为了你]

DataSet ds =new DataSet();

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