WPF中DataGrid绑定List<T>怎么没成功？


namespace XXXXX
{
    struct sREG 
    {
        public DateTime REGDatetime;
        public string REGENo;
        public string EName;
        public bool REGRed;
        public string REGStyle;
        public double REGCost;
    }    public partial class REquipmentG : Window
    {
        List<sREG> _listREG = new List<sREG>();        //………………………………
        //………………………………
        //………………………………        //初始化DataGrid的函数
        private bool InitialDataGrid()
        {
            try
            {
                SqlDataReader reader = null;
                //CommonFunction.SQLSearch此函数返回个Reader
                CommonFunction.SQLSearch("select REGDatetime,REGENo,EName,REGRed,REGStyle,REGCost from tEquipments,tREG where tREG.REGENo=tEquipments.ENo", ref MainWindow._cnn, ref reader);
                while (reader.Read())
                {
                    sREG tempsREG = new sREG();
                    tempsREG.REGDatetime = Convert.ToDateTime(reader[0]);
                    tempsREG.REGENo = Convert.ToString(reader[1]);
                    tempsREG.EName = Convert.ToString(reader[2]);
                    tempsREG.REGRed = Convert.ToBoolean(reader[3]);
                    tempsREG.REGStyle = Convert.ToString(reader[4]);
                    tempsREG.REGCost = Convert.ToDouble(reader[5]);                    _listREG.Add(tempsREG);
                }
                dgMain.ItemsSource = _listREG;
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
                return false;
            }            //MessageBox.Show(_listREG[0].EName);            return true;
        }
   }
}    <Canvas >
        <DataGrid x:Name="dgMain" Width="400" Height="300"/>
    </Canvas>
为什么DataGrid什么内容页不显示？