WinForm中访问OPC变量提示‘当前上下文不存在’问题求助

使用TitaniumAS开发了一款连接OPC服务器并进行数据读写的程序，控制台环境下运行正常。改为Windows Form应用后，按钮点击事件中无法访问相关方法与变量，报错：The name 'ascon1' does not exist in the current context。

原代码 #

using TitaniumAS.Opc.Client.Common;
using TitaniumAS.Opc.Client.Da;
using TitaniumAS.Opc.Client.Da.Browsing;
using System.Threading;
using System.Threading.Channels;


namespace OPCtests
{

    public partial class Form1 : Form
    {
        public Form1()
        {
            TitaniumAS.Opc.Client.Bootstrap.Initialize();

            Uri url = UrlBuilder.Build("Kepware.KEPServerEX.V6");

            using (var server = new OpcDaServer(url))
            {
                server.Connect();

                OpcDaGroup group = server.AddGroup("MyGroup");
                group.IsActive = true;

                Ascon ascon1 = new Ascon();

                ascon1.ALM = ReadX("Channel1.Ascon1.AsconS");


                void WriteX(String Link, String Ascon)
                {
                    var definition1 = new OpcDaItemDefinition
                    {
                        ItemId = Link,
                        IsActive = true
                    };

                    OpcDaItemDefinition[] definitions = { definition1 };
                    OpcDaItemResult[] results = group.AddItems(definitions);

                    OpcDaItem tag = group.Items.FirstOrDefault(i => i.ItemId == Link);
                    OpcDaItem[] items = { tag };

                    object[] Values = { Ascon };
                    HRESULT[] Results = group.Write(items, Values);

                }
                string ReadX(String Link)
                {
                    var definition1 = new OpcDaItemDefinition
                    {
                        ItemId = Link,
                        IsActive = true
                    };

                    OpcDaItemDefinition[] definitions = { definition1 };
                    OpcDaItemResult[] results = group.AddItems(definitions);
                    OpcDaItemValue[] values = group.Read(group.Items, OpcDaDataSource.Device);

                    return Convert.ToString(values[0].Value);
                }
            }

            InitializeComponent();
        }

        void Read_Click(object sender, EventArgs e)
        {
            textBox1.Text = ascon1.ALM;
        }
    }
}

• 修正变量作用域：原代码中ascon1、server、group以及ReadX/WriteX方法都定义在构造函数的using代码块内部，属于局部成员，外部事件无法访问。需要将这些成员提升为Form类的字段：
  1. 在Form类顶部添加类级字段：

     private OpcDaServer _server;
     private OpcDaGroup _group;
     private Ascon _ascon1;
     

  2. 移除构造函数中的using块（server需要保持连接状态，不能在构造函数结束后被自动释放），改为在Form关闭时手动释放资源。
• 迁移方法到类级别：将ReadX和WriteX从构造函数内部移到Form类中，作为成员方法，确保事件处理程序能调用。
• 调整初始化顺序：把InitializeComponent();放在构造函数最开始，保证WinForm控件先初始化完成，再执行OPC连接逻辑。

修改后示例代码 #

using TitaniumAS.Opc.Client.Common;
using TitaniumAS.Opc.Client.Da;
using TitaniumAS.Opc.Client.Da.Browsing;
using System.Threading;
using System.Threading.Channels;

namespace OPCtests
{
    public partial class Form1 : Form
    {
        private OpcDaServer _server;
        private OpcDaGroup _group;
        private Ascon _ascon1;

        public Form1()
        {
            InitializeComponent();
            InitializeOpcConnection();
        }

        private void InitializeOpcConnection()
        {
            TitaniumAS.Opc.Client.Bootstrap.Initialize();
            Uri url = UrlBuilder.Build("Kepware.KEPServerEX.V6");
            
            _server = new OpcDaServer(url);
            _server.Connect();
            
            _group = _server.AddGroup("MyGroup");
            _group.IsActive = true;
            
            _ascon1 = new Ascon();
            _ascon1.ALM = ReadX("Channel1.Ascon1.AsconS");
        }

        private void WriteX(string link, string asconValue)
        {
            var definition1 = new OpcDaItemDefinition
            {
                ItemId = link,
                IsActive = true
            };

            OpcDaItemDefinition[] definitions = { definition1 };
            OpcDaItemResult[] results = _group.AddItems(definitions);

            OpcDaItem tag = _group.Items.FirstOrDefault(i => i.ItemId == link);
            if (tag == null) return;
            
            OpcDaItem[] items = { tag };
            object[] values = { asconValue };
            HRESULT[] writeResults = _group.Write(items, values);
        }

        private string ReadX(string link)
        {
            var definition1 = new OpcDaItemDefinition
            {
                ItemId = link,
                IsActive = true
            };

            OpcDaItemDefinition[] definitions = { definition1 };
            OpcDaItemResult[] results = _group.AddItems(definitions);
            
            OpcDaItemValue[] values = _group.Read(_group.Items, OpcDaDataSource.Device);
            return values.Length > 0 ? Convert.ToString(values[0].Value) : string.Empty;
        }

        private void Read_Click(object sender, EventArgs e)
        {
            textBox1.Text = _ascon1.ALM;
        }

        private void Form1_FormClosing(object sender, FormClosingEventArgs e)
        {
            _group?.Dispose();
            if (_server != null && _server.IsConnected)
            {
                _server.Disconnect();
            }
            _server?.Dispose();
        }
    }
}

内容的提问来源于stack exchange，提问作者Seyl