本篇文章主要利用PISDK從PI服務器取數，介紹多種取數方法。
首先需要一些基礎的代碼，比如獲取PI服務的：
/// <summary>
/// 獲取PI服務/// </summary>
/// <param name="servername">//UID=PIUser;PWD=PIUserPassWord
</param>
/// <returns></returns>
private Server GetServer(string servername)
{
try
{
if (!string.IsNullOrEmpty(servername))
{
//采用認證方式登錄
server = pi.Servers[servername];
server.Open(connStr);
}
else
{
//采用默認方式登錄
server = pi.Servers.DefaultServer;
server.Open();
}
if (server.Connected)
{
return server;
}
else
{
return null;
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
return null;
}
}
還有到PI服務器中找點的方法：
/// <summary>
/// 搜索PI中對應的數據點
/// </summary>
/// <param name="server">PI服務對象</param>
/// <param name="condition">選擇tag的條件</param>
/// <returns></returns>
private PointList SearchPIPoints(Server server, String condition)
{
return server.GetPoints(condition);
}
下面介紹取數方法：
1. 取得單個tag快照值
/// <summary>
/// 取得單個tag快照值
/// </summary>
/// <param name="server">PI服務對象</param>
/// <param name="tag">tag名稱</param>
/// <returns></returns>
private string GetSingleSnap(Server server, string tag)
{
string output=string.Empty;
PIPoints piPoints = server.PIPoints;
//采用標簽名稱的方式取得對象
PIPoint piPoint = piPoints[tag];
//調用方法取得快照值
PIValue piValue = piPoint.Data.Snapshot;
//取到該快照值時PI服務器時間
PITimeServer.PITime piTime = piValue.TimeStamp;
output = piTime.LocalDate.ToString() + " " + piValue.Value + Environment.NewLine;
return output;
}
2. 取得單個tag一段時間內的歷史值
/// <summary>
/// 取得單個tag段時間內的歷史值
/// </summary>
/// <param name="server">PI服務對象</param>
/// <param name="tag">tag名稱</param>
/// <returns></returns>
private string GetSingleHistory(Server server, string tag)
{
string output = string.Empty;
PIPoints piPoints = server.PIPoints;
PIPoint piPoint = piPoints[tag];
//取得分鍾前到當前時間的歷史值
PIValues piValues = piPoint.Data.RecordedValues(DateTime.Now.AddMinutes(-5).ToString(),
DateTime.Now.ToString());
foreach (PIValue piValue in piValues)
{
PITimeServer.PITime piTime = piValue.TimeStamp; //PI時間
output += piTime.LocalDate.ToString() + " " + piValue.Value + Environment.NewLine;
}
return output;
}
3. 取得多個tag快照值
/// <summary>
/// 取得多個tag取快照值
/// </summary>
/// <param name="server">PI服務對象</param>
/// <param name="tag">tag值(tag='' or tag='')</param>
/// <returns></returns>
private string MultipleSnap(Server server, string tag)
{
string output = string.Empty;
//取tag
PointList ptlist = SearchPIPoints(server, tag);
PISDKCommon.NamedValues nvErrs = new PISDKCommon.NamedValues();
PointValues ptvalues = ptlist.Data.get_Snapshot(out nvErrs);
foreach (PointValue myValue in ptvalues)
{
PITimeServer.PITime piTime = myValue.PIValue.TimeStamp; //PI時間
if (myValue.PIValue.Value.GetType().IsCOMObject)
{
//狀態值
DigitalState myDigState = (DigitalState)myValue.PIValue.Value;
output += myValue.PIPoint.Name + " " + piTime.LocalDate.ToString() + " " + myDigState.Name + Environment.NewLine;
}
else
{
//模擬值
output += myValue.PIPoint.Name + " " + piTime.LocalDate.ToString() + " " + Convert.ToString(Math.Round(double.Parse(Convert.ToString(myValue.PIValue.Value)), 2)) + Environment.NewLine;
}
}
return output;
}
4. 取得多個tag一段歷史時間所有值
/// <summary>
/// 取得多個tag段歷史時間所有值
/// </summary>
/// <param name="server">PI服務對象</param>
/// <param name="tag">tag名稱</param>
/// <returns></returns>
private string MultipleHistory1(Server server,string tag)
{
string output = string.Empty;
PointList ptlist = SearchPIPoints(server, tag);
string outPut = string.Empty;
PISDKCommon.NamedValues nvErrs = new PISDKCommon.NamedValues();
foreach (PIPoint piPoint in ptlist)
{
//獲取5分鍾前到當前時間的歷史值
PIValues piValues = piPoint.Data.RecordedValues(DateTime.Now.AddMinutes(-5).ToString(),
DateTime.Now.ToString());
foreach (PIValue piValue in piValues)
{
PITimeServer.PITime piTime = piValue.TimeStamp; //PI時間
output+= piPoint.Name + " " + piTime.LocalDate.ToString() + " " + piValue.Value + Environment.NewLine;
}
}
return output;
}
5. 取得多個tag歷史時刻值
/// <summary>
/// 取得多個tag段歷史時間點值
/// </summary>
/// <param name="server">PI服務對象</param>
/// <param name="tag">tag名稱</param>
/// <returns></returns>
private string MultipleHistory2(Server server, string tag)
{
string output = string.Empty;
PointList ptlist = SearchPIPoints(server, tag);
PISDKCommon.NamedValues nvErrs = new PISDKCommon.NamedValues();
PITimeServer.PITimeFormat piTime1 = new PITimeServer.PITimeFormat();
piTime1.InputString = "*-2h";//or "2012-2-2 2:2:2"
//獲取兩小時前的時刻值
PointValues ptvalues = ptlist.Data.ArcValue(piTime1, RetrievalTypeConstants.rtAuto, out nvErrs);
foreach (PointValue myValue in ptvalues)
{
PITimeServer.PITime piTime = myValue.PIValue.TimeStamp; //PI時間
if (myValue.PIValue.Value.GetType().IsCOMObject)
{
//狀態值
DigitalState myDigState = (DigitalState)myValue.PIValue.Value;
output+= myValue.PIPoint.Name + " " + piTime.LocalDate.ToString() + " " + myDigState.Name + Environment.NewLine;
}
else
{
//模擬值
output+= myValue.PIPoint.Name + " " + piTime.LocalDate.ToString() + " " + Convert.ToString(Math.Round(double.Parse(Convert.ToString(myValue.PIValue.Value)), 2)) + Environment.NewLine;
}
}
return output;
}
以上主要介紹了如何去從PI服務器獲取值，包括了獲取單個tag和多個tag，也包括了獲取快照值和歷史值，也許從效率上來看並不是最優的，因為PI服務器版本限制，導致一些新的接口不能使用，如果您對效率有嚴格的要求，推薦您使用最新版本。
根據上述的方法，我們也可以制作一個小程序，界面如下：
