C# sample code that reads an item from an OPC server

Using the QuickUse Classes

Using the OpcGroup Class


using System;
using OPC;
using OPCDA;
using OPCDA.NET;

namespace OpcDemo {
   public class Demo {
      string ServerAccess() {
         OpcServer Srv = new OpcServer() ;
         int rtc = Srv.Connect( "Advosol.SimDAServer.1" );
         if( HRESULTS.Failed( rtc )
            return Srv.GetErrorString( rtc );

         SyncIOGroup srwGroup = new SyncIOGroup( Srv ) ;
         OPCItemState Rslt ;
         int rtc = srwGroup.Read( OPCDATASOURCE.OPC_DS_CACHE, 
            "SimulatedData.Step", out Rslt );
         string retVal;
         if( HRESULTS.Failed(rtc) )
            retVal = "Read error" ;
         else
            retVal = "data="+ Rslt.DataValue.ToString();
         srwGroup.Dispose();
         Srv.Disconnect();
         return retVal ;
      }
   }


using System;
using System.Runtime.InteropServices;
using OPC;
using OPCDA;
using OPCDA.NET;

namespace VCSSampleClient {
   public class DemoOpc  {
      public string ServerAccessOpc()  {
         OpcServer Srv = new OpcServer() ;
         int rtc = Srv.Connect( "Advosol.SimDAServer.1" );
         if( HRESULTS.Failed( rtc )
            return Srv.GetErrorString( rtc );
 
         OpcGroup oGrp ;
         float deadBand = 0.0F;
         try {
            oGrp = Srv.AddGroup( "Grp1",
                              true, 500, ref deadBand, 0, 0 );
         catch( Exception ex )  
         {
            Srv.Disconnect();
            return ex.Message ;
         }
         OPCItemDef[] items = new OPCItemDef[1];
         items[0] = new OPCItemDef( "SimulatedData.Step", 
                              true, 0, VarEnum.VT_BSTR );
         OPCItemResult[] addRslt = new OPCItemResult[1];
         int rtc = oGrp.AddItems( items, out addRslt ) ;
         if( HRESULTS.Failed(rtc) )   {
            Srv.Disconnect();
            return "Error at AddItem" ;
         }
         int[] iHnd = new Int32[1];
         iHnd[0] = addRslt[0].HandleServer ;
         OPCItemState[] rslt ;
         rtc = oGrp.Read( OPCDATASOURCE.OPC_DS_CACHE, 
                               iHnd, out rslt );
         string retVal;
         if( HRESULTS.Failed(rtc) )
            retVal = "Read error" ;
         else
            if(  HRESULTS.Failed(rslt[0].Error) )
               retVal = "Item Read error" ;
         else
            retVal = "data="+ rslt[0].DataValue.ToString();
         oGrp.Remove(true);
         Srv.Disconnect();
         return retVal ;

      }
   }
}

See the Controls chapter for sample application code based on the DAServer/DAGroup Visual Studio controls.

A number of sample client applications including the Visual Studio project are in the OPCDA.NET installation sub-folder C# Sample Clients.

If you don't find this folder then probably the sample installation option was not selected when OPCDA.NET was installed.

The Visual Studio project wizard creates a Windows Form application with sample code according the selections in the wizard dialog. It may be quicker to create a new project with the required features than search for a matching sample application.

If you don't find the OPCDA.NET client template in the Visual Studio Add New Project template selection then probably the C# wizard installation option was not selected when OPCDA.NET was installed.