string cnn = ConfigurationManager.ConnectionStrings["ReportDataService"].ConnectionString;
using (SqlConnection cn = new SqlConnection())
{
cn.ConnectionString = cnn;
cn.Open();
SqlCommand cmd = new SqlCommand();
cmd.Connection = cn;
cmd.CommandText = "select * from yourTable";
SqlDataAdapter da = new SqlDataAdapter(cmd);
DataSet ds = new DataSet();
da.Fill(ds);
ds.Tables[0] 这个就是你的数据
}