本篇文章主要利用PISDK从PI服务器取数，介绍多种取数方法。
首先需要一些基础的代码，比如获取PI服务的：
/// <summary>
/// 获取PI服务/// </summary>
/// <param name="servername">//UID=PIUser;PWD=PIUserPassWord
</param>
/// <returns></returns>
private Server GetServer(string servername)
{
try
{
if (!string.IsNullOrEmpty(servername))
{
//采用认证方式登录
server = pi.Servers[servername];
server.Open(connStr);
}
else
{
//采用默认方式登录
server = pi.Servers.DefaultServer;
server.Open();
}
if (server.Connected)
{
return server;
}
else
{
return null;
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
return null;
}
}
还有到PI服务器中找点的方法：
/// <summary>
/// 搜索PI中对应的数据点
/// </summary>
/// <param name="server">PI服务对象</param>
/// <param name="condition">选择tag的条件</param>
/// <returns></returns>
private PointList SearchPIPoints(Server server, String condition)
{
return server.GetPoints(condition);
}
下面介绍取数方法：
1. 取得单个tag快照值
/// <summary>
/// 取得单个tag快照值
/// </summary>
/// <param name="server">PI服务对象</param>
/// <param name="tag">tag名称</param>
/// <returns></returns>
private string GetSingleSnap(Server server, string tag)
{
string output=string.Empty;
PIPoints piPoints = server.PIPoints;
//采用标签名称的方式取得对象
PIPoint piPoint = piPoints[tag];
//调用方法取得快照值
PIValue piValue = piPoint.Data.Snapshot;
//取到该快照值时PI服务器时间
PITimeServer.PITime piTime = piValue.TimeStamp;
output = piTime.LocalDate.ToString() + " " + piValue.Value + Environment.NewLine;
return output;
}
2. 取得单个tag一段时间内的历史值
/// <summary>
/// 取得单个tag段时间内的历史值
/// </summary>
/// <param name="server">PI服务对象</param>
/// <param name="tag">tag名称</param>
/// <returns></returns>
private string GetSingleHistory(Server server, string tag)
{
string output = string.Empty;
PIPoints piPoints = server.PIPoints;
PIPoint piPoint = piPoints[tag];
//取得分钟前到当前时间的历史值
PIValues piValues = piPoint.Data.RecordedValues(DateTime.Now.AddMinutes(-5).ToString(),
DateTime.Now.ToString());
foreach (PIValue piValue in piValues)
{
PITimeServer.PITime piTime = piValue.TimeStamp; //PI时间
output += piTime.LocalDate.ToString() + " " + piValue.Value + Environment.NewLine;
}
return output;
}
3. 取得多个tag快照值
/// <summary>
/// 取得多个tag取快照值
/// </summary>
/// <param name="server">PI服务对象</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时间
if (myValue.PIValue.Value.GetType().IsCOMObject)
{
//状态值
DigitalState myDigState = (DigitalState)myValue.PIValue.Value;
output += myValue.PIPoint.Name + " " + piTime.LocalDate.ToString() + " " + myDigState.Name + Environment.NewLine;
}
else
{
//模拟值
output += myValue.PIPoint.Name + " " + piTime.LocalDate.ToString() + " " + Convert.ToString(Math.Round(double.Parse(Convert.ToString(myValue.PIValue.Value)), 2)) + Environment.NewLine;
}
}
return output;
}
4. 取得多个tag一段历史时间所有值
/// <summary>
/// 取得多个tag段历史时间所有值
/// </summary>
/// <param name="server">PI服务对象</param>
/// <param name="tag">tag名称</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)
{
//获取5分钟前到当前时间的历史值
PIValues piValues = piPoint.Data.RecordedValues(DateTime.Now.AddMinutes(-5).ToString(),
DateTime.Now.ToString());
foreach (PIValue piValue in piValues)
{
PITimeServer.PITime piTime = piValue.TimeStamp; //PI时间
output+= piPoint.Name + " " + piTime.LocalDate.ToString() + " " + piValue.Value + Environment.NewLine;
}
}
return output;
}
5. 取得多个tag历史时刻值
/// <summary>
/// 取得多个tag段历史时间点值
/// </summary>
/// <param name="server">PI服务对象</param>
/// <param name="tag">tag名称</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"
//获取两小时前的时刻值
PointValues ptvalues = ptlist.Data.ArcValue(piTime1, RetrievalTypeConstants.rtAuto, out nvErrs);
foreach (PointValue myValue in ptvalues)
{
PITimeServer.PITime piTime = myValue.PIValue.TimeStamp; //PI时间
if (myValue.PIValue.Value.GetType().IsCOMObject)
{
//状态值
DigitalState myDigState = (DigitalState)myValue.PIValue.Value;
output+= myValue.PIPoint.Name + " " + piTime.LocalDate.ToString() + " " + myDigState.Name + Environment.NewLine;
}
else
{
//模拟值
output+= myValue.PIPoint.Name + " " + piTime.LocalDate.ToString() + " " + Convert.ToString(Math.Round(double.Parse(Convert.ToString(myValue.PIValue.Value)), 2)) + Environment.NewLine;
}
}
return output;
}
以上主要介绍了如何去从PI服务器获取值，包括了获取单个tag和多个tag，也包括了获取快照值和历史值，也许从效率上来看并不是最优的，因为PI服务器版本限制，导致一些新的接口不能使用，如果您对效率有严格的要求，推荐您使用最新版本。
根据上述的方法，我们也可以制作一个小程序，界面如下：
