如何：WCF 服务检查 Windows 窗体用户是否仍处于活动状态？

Question

我有以下场景：一个 Windows Mobile 6.1 (.NET Compact Framwork 2.0) Forms 应用程序（同时在多个设备上运行），它使用来自服务器的多个 WCF 服务。要使用 windows 窗体应用程序，用户必须登录。

服务器使用来自 SAP 系统的数据。 WCF 服务器必须根据记录的用户从 SAP 检索一些信息。因此，我的 Windows 窗体应用程序必须（不时）显示它们仍在运行到我的 WCF 服务器。

我可以做些什么来完成这项任务？我正在考虑创建一个更新 WCF 服务器的 SQL 服务器的后台任务。 （就像一个会话控件）。

Answer 1

您可以在您的应用程序中监听Power State 的更改。文档显示它仅适用于 Windows Mobile 6.5，但我在运行 .NET CF 3.5 的 Windows Mobile 5.0 应用程序中使用它。

就像手机一样，如果移动设备长时间不使用，操作系统会显示电池电量处于同一水平，直到实际使用为止。所以，它不是很可靠。

但是，您可以侦听事件（like POWER_STATE_CRITICAL 等）并让您的软件进行相应的更改以与您的 WCF 服务器交互。

下面是我使用的东西的编辑版本。

这不会 100% 解决您的问题，但它应该让您了解如何做您需要的事情。

using Microsoft.WindowsMobile.Status;

BatteryLevel _batteryLevel;
BatteryState _batteryState;

void Mobile5_Load(object sender, EventArgs e) {
  _batteryLevel = (BatteryLevel)SystemState.GetValue(SystemProperty.PowerBatteryStrength);
  _batteryState = (BatteryState)SystemState.GetValue(SystemProperty.PowerBatteryState);
  if (!BatteryCritical(false)) {
    // Continue
  }
}
/// <summary>
/// Sets the Battery Level and Battery State for the Mobile Device
/// <para><value>showDialog=True show the dialog box</value></para>
/// <para><value>Returns True <b>if</b> the battery is in a critical state</value></para>
/// </summary>
/// <param name="showDialog">Do you want a dialog box to be displayed or not?</param>
/// <returns>false if the Battery is NOT in the critical state</returns>
bool BatteryCritical(bool showDialog) {
  _batteryAlert = false;
  bool bad = false; // everything starts out ok. We are actually running, after all.
  _batteryLevel = (BatteryLevel)SystemState.GetValue(SystemProperty.PowerBatteryStrength);
  _batteryState = (BatteryState)SystemState.GetValue(SystemProperty.PowerBatteryState);
  bool present = ((_batteryState & BatteryState.NotPresent) != BatteryState.NotPresent);
  bool charging = ((_batteryState & BatteryState.Charging) == BatteryState.Charging);
  bool critical = ((_batteryState & BatteryState.Critical) == BatteryState.Critical);
  bool lowbatry = ((_batteryState & BatteryState.Low) == BatteryState.Low);
  Color c;
  if (present) {
    if (charging) {
      c = Color.Cyan;
    } else {
      if (critical) {
        c = Color.Orange;
        _batteryAlert = true;
      } else if (lowbatry) {
        c = Color.Yellow;
        _batteryAlert = true;
      } else {
        c = Color.White;
      }
    }
  } else {
    c = Color.Silver;
  }
  StatusPanel.BackColor = c;
  switch (_batteryLevel) {
    case BatteryLevel.VeryHigh: // (81-100%)
      BatteryPanel.BackColor = Color.Cyan;
      break;
    case BatteryLevel.High: // (61-80%)
      BatteryPanel.BackColor = Color.Lime;
      break;
    case BatteryLevel.Medium: // 41-60%)
      BatteryPanel.BackColor = Color.Yellow;
      break;
    case BatteryLevel.Low: // (21-40%)
      BatteryPanel.BackColor = Color.Orange;
      //WirelessUpdate(RadioState.Off, false);
      break;
    case BatteryLevel.VeryLow: // (0-20%)
      BatteryPanel.BackColor = Color.Red;
      //WirelessUpdate(RadioState.Off, false);
      bad = (!charging && present);
      break;
  }
  if (showDialog) {
    string msg = string.Format("Level is {0}\r\nState is {1}", _batteryLevel, _batteryState);
    if (_batteryLevel == BatteryLevel.Low) {
      msg += "\r\n\r\nThe wireless radio will be inactive until it has been charged.";
    } else if (bad == true) {
      msg += "\r\n\r\nThis Application will now close to preserve the device. Please return it to a charging base immediately.";
    }
    MessageBox.Show(msg, "Battery Meter", MessageBoxButtons.OKCancel, MessageBoxIcon.None, 0);
  }
  if (!bad) {
    StatusPanel.Refresh();
    // You could signal your app here
  } else {
    // Tell your app this device needs to turn off now.
  }
  return bad;
}