private static DataSet SelectRows(DataSet dataset,
    string connectionString,string queryString) 
{
    using (SqlConnection connection = 
        new SqlConnection(connectionString))
    {
        SqlDataAdapter adapter = new SqlDataAdapter();
        adapter.SelectCommand = new SqlCommand(
            queryString, connection);
        adapter.Fill(dataset);
        return dataset;
    }
}

//引入命名空间
using System;
using System.Data;
using System.Data.Common;
using System.Data.SqlClient;

class MainClass
{
  static void Main(string[] args)
  {
    SqlConnection SConn = new SqlConnection("Data Source=(local); Initial Catalog = CaseManager; Integrated Security=true");
    SqlDataAdapter da = new SqlDataAdapter("SELECT ID, FirstName, LastName FROM Employee", SConn);
    DataSet ds = new DataSet();
    DataTableMapping custMap = da.TableMappings.Add("Employee", "MyDatabase");
    custMap.ColumnMappings.Add("ID", "Number");
    custMap.ColumnMappings.Add("FirstName", "first name");
    custMap.ColumnMappings.Add("LastName", "last name");
    da.Fill(ds);
  }
}