Question

I have a windows form that involes filling out textboxes with information and then clicking connect. I have error messages that pops up if any of the textboxes are empty but when I hit OK the program just continues and I end up getting run-time errors because there’s insufficient information, and the program crashes. What I want is for the program to go back to the point before I hit “Connect” whenever any textbox is not filled out correctly.

This is the code:

private void cmdConnect_Click(object sender, EventArgs e)
    {

        if (cmdConnect.Text == "Connect")
        {
            if (txtGroup.Text == "")
            {
                txtGroup.Text = "_Group01";
            }

            if (txtItemID.Text == "")
            {
                MessageBox.Show("Please enter ItemID.", "Connect Error", MessageBoxButtons.OK, MessageBoxIcon.Error);

            }
                switch (cboServer.Text)
                {
                    case "":
                        MessageBox.Show("Please select and OPC server", "Connect Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                        break;


                    case "RSLinx Remote OPC Server":
                        if (txtMachine.Text == "")
                        {
                            MessageBox.Show("Please enter a machine name for remote connection", "Connect Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                            break;
                        }
                        else
                        {
                            oOpcServer.Connect(cboServer.Text, txtMachine.Text);
                        }
                        break;

                    case "RSLinx OPC Server":
                        oOpcServer.Connect(cboServer.Text);
                        break;

                    default:
                        if (txtMachine.Text == "")
                        {
                            oOpcServer.Connect(cboServer.Text);
                        }
                        else
                        {
                            oOpcServer.Connect(cboServer.Text, txtMachine.Text);


                        }
                        break;
            }
            oOpcGroup = oOpcServer.OPCGroups.Add(txtGroup.Text);
            oOpcGroup.IsSubscribed = true;
            oOpcGroup.IsActive = false;
            oOpcGroup.UpdateRate = 1000;


            ClHandle = 1;
            oOpcGroup.OPCItems.DefaultAccessPath = txtAccessPath.Text;
            oOpcGroup.OPCItems.AddItem(txtItemID.Text, ClHandle);

            cmdItemWrite.Enabled = true;
            cmdItemRead.Enabled = true;
            cmdSyncWrite.Enabled = true;
            cmdSyncRead.Enabled = true;
            cmdAsyncWrite.Enabled = true;
            cmdAsyncRead.Enabled = true;
            cmdAdvise.Enabled = true;
            txtSubValue.Enabled = true;
            cboServer.Enabled = false;
            txtMachine.Enabled = false;
            txtGroup.Enabled = false;
            txtAccessPath.Enabled = false;
            txtItemID.Enabled = false;

            cmdConnect.Text = "Disconnect";
        }
        else
        {
            oOpcServer.OPCGroups.RemoveAll();
            oOpcGroup = null;
            oOpcServer.Disconnect();

            cmdConnect.Text = "Connect";
            cmdItemWrite.Enabled = false;
            cmdItemRead.Enabled = false;
            cmdSyncWrite.Enabled = false;
            cmdSyncRead.Enabled = false;
            cmdAsyncWrite.Enabled = false;
            cmdAsyncRead.Enabled = false;
            cmdAdvise.Enabled = false;
            txtSubValue.Enabled = false;
            cboServer.Enabled = true;
            txtMachine.Enabled = true;
            txtGroup.Enabled = true;
            txtAccessPath.Enabled = true;
            txtItemID.Enabled = true;
        }
        oOpcGroup.DataChange += new RsiOPCAuto.DIOPCGroupEvent_DataChangeEventHandler(oOpcGroup_DataChange);
    }

Answer 1

Adding a return statment after each message box would do the trick and cause the method to exit without doing the work at end.