c#CommabdTest属性尚未初始化

Question

#region 查询按钮
private void btnSearch_Click(object sender, EventArgs e)
{
////刷新数据
//BindData();
//btnChangeInfo.Enabled = true;
//btnSave.Enabled = false;
//btnCancel.Enabled = true;
//btnDelete.Enabled = true;
DBHelper.connection.Open();
DataTable set = new DataTable();
SqlDataAdapter da = new SqlDataAdapter();
string sql =String.Empty;
if (txtRoomName.Text != "" && txtRoomJC.Text != "" && txtRoomBJF.Text != "" && txtRoomWZ.Text != "" && txtRoomBeiZhu.Text != "")
{
sql = String.Format("select a.RoomName'桌台名称',a.RoomJC'桌台简称', a.RoomBJF'包间费',a.RoomWZ'桌台位置',a.RoomType'桌台类型',a.RoomBZ'备注' from tb_Room a where a.RoomName='{0}' and a.RoomJC='{1}' and a.RoomBJF='{2}'and a.RoomWZ='{3}' and a.RoomBZ='{4}'", txtRoomName.Text, txtRoomJC.Text, txtRoomBJF.Text, txtRoomWZ.Text, txtRoomBeiZhu.Text);
}
else if (txtRoomName.Text != "" && txtRoomJC.Text != "" && txtRoomBJF.Text != "" && txtRoomWZ.Text != "")
{
sql = String.Format("select a.RoomName'桌台名称',a.RoomJC'桌台简称', a.RoomBJF'包间费',a.RoomWZ'桌台位置',a.RoomType'桌台类型',a.RoomBZ'备注' from tb_Room a where a.RoomName='{0}' and a.RoomJC='{1}' and a.RoomBJF='{2}'and a.RoomWZ='{3}'", txtRoomName.Text, txtRoomJC.Text, txtRoomBJF.Text, txtRoomWZ.Text);
}
else if (txtRoomName.Text != "" && txtRoomJC.Text != "" && txtRoomBJF.Text != "")
{
sql = String.Format("select a.RoomName'桌台名称',a.RoomJC'桌台简称', a.RoomBJF'包间费',a.RoomWZ'桌台位置',a.RoomType'桌台类型',a.RoomBZ'备注' from tb_Room a where a.RoomName='{0}' and a.RoomJC='{1}' and a.RoomBJF='{2}'", txtRoomName.Text, txtRoomJC.Text, txtRoomBJF.Text);
}
else if (txtRoomName.Text != "" && txtRoomJC.Text != "")
{
sql = String.Format("select a.RoomName'桌台名称',a.RoomJC'桌台简称', a.RoomBJF'包间费',a.Roo mWZ'桌台位置',a.RoomType'桌台类型',a.RoomBZ'备注' from tb_Room a where a.RoomName='{0}' and a.RoomJC='{1}' and a.RoomBJF='{2}'", txtRoomName.Text, txtRoomJC.Text);
}
else if (txtRoomName.Text != "")
{
sql = String.Format("select a.RoomName'桌台名称',a.RoomJC'桌台简称', a.RoomBJF'包间费',a.RoomWZ'桌台位置',a.RoomType'桌台类型',a.RoomBZ'备注' from tb_Room a where a.RoomName='{0}' and a.RoomJC='{1}'", txtRoomName.Text);
}
da = new SqlDataAdapter(sql,DBHelper.connection);
da.Fill(set);
dgvRoomDetails.DataSource = set;
DBHelper.connection.Close();

    }
    #endregion