why am i getting the error "Unable to cast object of type 'OpcCom.Factory' to type 'Opc.IFactory'."?

Question

I am using the OPC Foundation .NET API, with Visual Studio 2012. When I try to connect I get this error:

Unable to cast object of type 'OpcCom.Factory' to type 'Opc.IFactory'

...at the instruction new Opc.Da.Server( in this code:

private void button1_Click(object sender, EventArgs e)
{
    Opc.Da.Server plcServer = null;

    string serverUrl = "opcda://localhost/RSLinx OPC Server";

    plcServer = new Opc.Da.Server(new OpcCom.Factory(), new Opc.URL(serverUrl));
    plcServer.Connect();
}

Answer 1

The problem was the version of rslinx i am using, the rslinx installed the opc .net api version 1.3 (i didn't know this) and then i installed the opc .net api 2.0 to make my opc client, so when i added the references i didn't notice that i have 2 versions of the dll's, i only picked the first i saw in the list.

At the end i was using the OpcNetApi.dll 2.0 and the OpcNetApi.Com.dll 1.3. And that's why it was throwing that error.

Answer 2

It's throwing this error because the interface for Opc.Da.Server is expecting an Opc.IFactory, but what's returned from OpcCom.Factory() does not implement that interface.