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Back to Services Source Examples
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Reading Tags in an NT Service application using OPC Web Client Web Service
 Reading Single Tags
string strPCName = "";
string strOPCServer = "OPCLabs.KitServer.2";
string strTag = "Simulation.Random";
string strAccessPath = "";
int iDataType = 0;
try
{
//create our opc web client object
OPCLabs.EasyOPCDANet.EasyDAWS objOWC = new OPCLabs.EasyOPCDANet.EasyDAWS();
//create our vtq object to receive the reading
OPCLabs.EasyOPCDANet.IVTQNet objTagVTQ;
//make the call to get the tag reading
objTagVTQ = objOWC.ReadItem(strPCName, strOPCServer, strTag, strAccessPath,
iDataType, null);
//like any good coder, we check the quality of the tag
if(objTagVTQ.Quality >= 192)
{
MessageBox.Show("Value: " + objTagVTQ.Value.ToString()
+ " Quality: " + objTagVTQ.Quality.ToString()
+ " Timestamp: " + objTagVTQ.Timestamp.ToString());
}
else
{
MessageBox.Show("BAD QUALITY TAG! " + objTagVTQ.Quality.ToString());
}
//now to clean-up
objTagVTQ = null;
objOWC = null;
}
catch(System.Web.Services.Protocols.SoapException webex)
{
MessageBox.Show("Error: " + webex.Message.ToString());
}
catch(Exception ex)
{
MessageBox.Show("Error: " + ex.Message.ToString());
}
Reading Multiple Tags
try
{
//define our initial variables and set their values
object oPC = "127.0.0.1";
object oOPC = "OPCLabs.KitServer.2";
object oTags = new object[]{"Simulation.Random", "Trends.Ramp (1 min)"};
object oAccess = System.Runtime.InteropServices.VarEnum.VT_ERROR;
object oDTypes = System.Runtime.InteropServices.VarEnum.VT_ERROR;
object oModes = System.Runtime.InteropServices.VarEnum.VT_ERROR;
//'create the opc web client object
OPCLabs.EasyOPCDANet.EasyDAWS o = new OPCLabs.EasyOPCDANet.EasyDAWS();
//make the call to read multiple tags
object values = (object)o.ReadMultipleItemValues(
oPC,
oOPC,
oTags,
null,
null,
null);
//string needed to generate output message
System.Text.StringBuilder sb = new System.Text.StringBuilder();
//create an array so we can iterate thru it
Array ar = (Array)values;
//iterate thru array
for(int i = 0; i < ar.GetLength(0); i++)
{
//build-up our string message
sb.Append("Value: " + ar.GetValue(i) + "\n");
}
//display the message output to screen
MessageBox.Show(sb.ToString());
}
catch(System.Web.Services.Protocols.SoapException webex)
{
MessageBox.Show("Error: " + webex.Message.ToString());
}
catch(Exception ex)
{
//'send exception messages to the screen
MessageBox.Show("Err: " + ex.Message.ToString());
}
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