c# - 在主线程上使用大型全局对象时，如何不从工作线程中阻止主UI线程

Question

我正在使用用于证件扫描器的外部库，为简单起见，我将其称为ScanLib。扫描过程很长，当然，在调用诸如ScanLib.Scan()之类的方法时，它往往会阻塞UI线程，因此我认为这是使用Tasks的绝佳时机。这里是用于上下文的简化(或TLDR)代码(下面的完整代码以获取更多详细信息，但为了节省时间，此处进行了总结):

public partial class MainForm : Form () 
{
//Here I initialize the reference variable which I will use to work with the Scanner library
ScanLib scanLibraryReference = new ScanLib();

   // Form constructor
   public Form()
   {
      //This initializes the scanner and it's library components, it runs until the program closes
      Task scannerInitTask = Task.Run(() => scanLibraryReference.InitializeScanLibrary())
      InitializeComponent();
   }

   private void Button_Click(object sender, EventArgs e) {
      Task scannerTask = Task.Run(() => scanLibraryReference.ScanCard()); 
   }
}

问题是，当我尝试扫描卡时，它冻结了主UI线程，即使很难，我也在其他任务中同时运行ScanLib.InitializeScanLib()和ScanLib.ScanCard()方法以尝试不阻塞主UI线程，因为后者很耗时。我已经阅读了主要UI线程阻塞的原因，并且我认为这可能是两件事之一:

我正在使用全局声明的scanLibraryReference变量来使用该库，甚至很难在任务中使用它，因为在变量上声明了它，所以在使用它时它可能会阻塞主UI线程。

根据文档，所有ScanLib方法都可能引发许多错误，这些错误以数字形式出现(错误1001、1002、1003等)，为了简化错误记录，文档要求我声明+100常量，类似于:public const int SCANLIB_ERR_SCANFAILED = 1001;。所有这些“错误常量”都在MainForm的public部分公共(public)类的另一个文件中声明，因此也许使用其他任务(线程)中的这些常量可能会冻结主UI线程

这些是我的主要嫌疑犯，但话虽如此，您可能会认为我会解决，但我没有解决，这就是我的问题所在:
在程序的整个过程中，我将一直需要ScanLib引用，但是如果在主UI线程上创建它，则会被阻塞。我可以尝试创建一个新任务，例如:
任务backgroundWorker = Task.Run(()=> {ScanLib scanLibRef =新的ScanLib(); scanLibRef.InitializeLibrary()});
但是据我了解，此变量现在将存在于此线程中，并且不能在另一个线程中使用，或者可以吗？甚至，即使我创建了一个简单的线程来仅容纳变量，该线程也将在声明完变量后死亡。我只是想通过Thread函数来做到这一点，但是随之而来的一个问题是，当我按下一个按钮并为其提供功能来运行扫描仪时，如何将其重新激活。谁能提出一个解决方案，说明如何声明需要不断使用的全局变量而不阻塞主UI线程？

请求完整的代码(很长，很抱歉，所有Console.WriteLines都用于调试)

    using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using ScannerTest;
using System.Threading;

namespace ScannerTest
{
    public partial class Form1 : Form
    {
        // All 4 variables below are global and used extensively to call scanner methods
        // Main Scan basic functions Library
        NetScanW.SLibEx scanSlibxEx = new NetScanW.SLibEx();
        // Main Scan extended functios Library
        NetScanW.CImage scanCImage = new NetScanW.CImage();
        // Main Scan OCR functions library
        NetScanW.IdData scanIdData = new NetScanW.IdData();
        // Main Scan extended functions 2 library
        NetScanWex.SLibEx scanWexSlibxEx = new NetScanWex.SLibEx();
        string ImageSource = @"C:\Scans\";

        public Form1()
        {
            Task initTask = Task.Run(() => InitScanLibraries());
            InitializeComponent();
            Console.WriteLine("\nForm initialized succesfully.");
        }

        #region Button events

        // The normal way of scanning which of course blocks the main UI thread
        private void ScanCardNonAsync_Click(object sender, EventArgs e)
        {
            Console.WriteLine("");
            Console.WriteLine("*********************");
            Console.WriteLine("Starting new scan...");
            string currentScan = ImageSource + "MyScan.bmp";
            string modifiedScan = ImageSource + "MyEditedScan.bmp";
            ScanCard(currentScan, modifiedScan);
            OCRscan();
            GetOCRData();
            Console.WriteLine("Scan finalized..");
            Console.WriteLine("*********************");
        }

        // My attempt at scanning asynchronously which still blocks the UI thread
        private void ScanCardAsync_Click(object sender, EventArgs e)
        {
            Console.WriteLine("");
            Console.WriteLine("*********************");
            Console.WriteLine("Starting new scan...");
            string currentScan = ImageSource + "MyScan.bmp";
            string modifiedScan = ImageSource + "MyEditedScan.bmp";
            // Here I chain the methods in a task chain to scan a Card
            Task ScannerStart = new Task(() => ScanCard(currentScan, modifiedScan));
            Task ScannerStep2 = ScannerStart.ContinueWith((x) => OCRscan());
            Task ScannerStep3 = ScannerStep2.ContinueWith((y) => GetOCRData());
            ScannerStart.Start();
        }

        #endregion

        #region Methods

        private void InitScanLibraries()
        {
            switch (scanSlibxEx.InitLibrary("49B2MFWE8WUJXLBW"))
            {
                case SLIB_ERR_SCANNER_BUSSY:
                    System.Console.WriteLine("ERROR: Scanner Busy...");
                    break;
                case LICENSE_VALID:
                    System.Console.WriteLine("");
                    System.Console.WriteLine("**********************************");
                    System.Console.WriteLine("SlibxEx initialized succesfully...");
                    break;
                case LICENSE_INVALID:
                    System.Console.WriteLine("ERROR: License Invalid");
                    break;
                case LICENSE_EXPIRED:
                    System.Console.WriteLine("ERROR: License Expired");
                    break;
                case SLIB_ERR_DRIVER_NOT_FOUND:
                    System.Console.WriteLine("ERROR: Driver not found");
                    break;
                case SLIB_ERR_SCANNER_NOT_FOUND:
                    System.Console.WriteLine("ERROR: Scanner not found");
                    break;
            }

            switch (scanIdData.InitLibrary("49B2MFWE8WUJXLBW"))
            {
                case SLIB_ERR_SCANNER_BUSSY:
                    System.Console.WriteLine("ERROR: Scanner Busy...");
                    break;
                case LICENSE_VALID:
                    System.Console.WriteLine("License validation succesful...");
                    break;
                case LICENSE_INVALID:
                    System.Console.WriteLine("ERROR: License Invalid");
                    break;
                case LICENSE_EXPIRED:
                    System.Console.WriteLine("ERROR: License Expired");
                    break;
                case SLIB_ERR_DRIVER_NOT_FOUND:
                    System.Console.WriteLine("ERROR: Driver not found");
                    break;
                case SLIB_ERR_SCANNER_NOT_FOUND:
                    System.Console.WriteLine("ERROR: Scanner not found");
                    break;
                case GENERAL_ERR_PLUG_NOT_FOUND:
                    System.Console.WriteLine("ERROR: Attatched scanner is not one of the following:\n ScanShell 600 \n ScanShell 800 \n ScanShell1000");
                    break;
                case SLIB_LIBRARY_ALREADY_INITIALIZED:
                    System.Console.WriteLine("ERROR: Call ignored, library already initialized");
                    break;
            }

        }

        private void ScanCard(string ImagePath, string ModifiedImagePath)
        {
            Console.WriteLine("Attempting scan...");

            switch (scanSlibxEx.ScanToFile(ImagePath))
            {
                case SLIB_ERR_NONE:
                    Console.WriteLine("Scan succesful...");
                    break;
                case SLIB_ERR_SCANNER_BUSSY:
                    Console.WriteLine("ERROR: Scanner is busy...");
                    break;
                case LICENSE_INVALID:
                    Console.WriteLine("ERROR: License invalid");
                    break;
                case SLIB_ERR_SCANNER_NOT_FOUND:
                    Console.WriteLine("ERROR: Scanner not found");
                    break;
                case SLIB_ERR_SCANNER_GENERAL_FAIL:
                    Console.WriteLine("ERROR: Scanner general fail");
                    break;
                case SLIB_ERR_HARDWARE_ERROR:
                    Console.WriteLine("ERROR: Hardware error");
                    break;
                case SLIB_ERR_PAPER_FED_ERROR:
                    Console.WriteLine("ERROR: Paper fed error");
                    break;
                case SLIB_ERR_SCANABORT:
                    Console.WriteLine("ERROR: Scan aborted");
                    break;
                case SLIB_ERR_NO_PAPER:
                    Console.WriteLine("ERROR: No paper");
                    break;
                case SLIB_ERR_PAPER_JAM:
                    Console.WriteLine("ERROR: Paper jammed");
                    break;
                case SLIB_ERR_FILE_IO_ERROR:
                    Console.WriteLine("ERROR: File I/O error");
                    break;
                case SLIB_ERR_PRINTER_PORT_USED:
                    Console.WriteLine("ERROR: Printer port used");
                    break;
                case SLIB_ERR_OUT_OF_MEMORY:
                    Console.WriteLine("ERROR: Out of memory");
                    break;
            }
            //scanCImage.RotateImage(ImageSource, 90, 1, ModifiedImagePath);

        }

        private void OCRscan()
        {
            Console.WriteLine("Attempting OCR extraction...");
            string data = "";
            int region = scanIdData.AutoDetectState(data);
            // Check for card region
            switch (region)
            {
                case ID_ERR_USA_TEMPLATES_NOT_FOUND:
                    Console.WriteLine("ERROR: No USA templates found");
                    break;
                case INVALID_INTERNAL_IMAGE:
                    Console.WriteLine("ERROR: No internal image loaded");
                    break;
                case ID_ERR_STATE_NOT_SUPORTED:
                    Console.WriteLine("ERROR: State not supported");
                    break;
                case ID_ERR_STATE_NOT_RECOGNIZED:
                    Console.WriteLine("ERROR: State not recognized");
                    break;
                default:
                    Console.WriteLine("Region catch succesful");
                    break;
            }

            // Begin OCR extraction
            string data2 = "";
            Console.WriteLine("Attempting data extraction...");
            switch (scanIdData.ProcState(data2, region))
            {
                case ID_TRUE:
                    Console.WriteLine("Data extraction succesful.");
                    break;
                case LICENSE_INVALID:
                    Console.WriteLine("ERROR: LICENSE_INVALID");
                    break;
                case SLIB_ERR_SCANNER_NOT_FOUND:
                    Console.WriteLine("ERROR: SLIB_ERR_SCANNER_NOT_FOUND. ");
                    break;
                case SLIB_ERR_INVALID_SCANNER:
                    Console.WriteLine("ERROR: SLIB_ERR_INVALID_SCANNER. ");
                    break;
                case ID_ERR_STATE_NOT_SUPORTED:
                    Console.WriteLine("ERROR: ID_ERR_STATE_NOT_SUPORTED. ");
                    break;
                case INVALID_INTERNAL_IMAGE:
                    Console.WriteLine("ERROR: INVALID_INTERNAL_IMAGE. ");
                    break;
                default:
                    Console.WriteLine("ERROR: Uncatched exception in Form1.OCRScan()");
                    break;
            }
            // Data copying to local
            Console.WriteLine("Copying data locally...");
            if (scanIdData.RefreshData() != 0) Console.WriteLine("Data copied succesfully."); else Console.WriteLine("ERROR: Problem while copying data");
        }

        private void GetOCRData()
        {
            //loc* Variables are locally declared global variables, while the scanIdData.* are library variables where OCR scan results are saved
            Console.WriteLine("Saving data locally...");
            locName = scanIdData.Name;
            locNameFirst = scanIdData.NameFirst;
            locNameMiddle = scanIdData.NameMiddle;
            locNameLast = scanIdData.NameLast;
            locNameSuffix = scanIdData.NameSuffix;
            locID = scanIdData.Id;
            locLicense = scanIdData.license;
            locIssueDate = scanIdData.IssueDate;
            locAddress = scanIdData.Address;
            locExperationDate = scanIdData.ExpirationDate;
            locCSC = scanIdData.CSC;
            locCity = scanIdData.City;
            locEyes = scanIdData.Eyes;
            locDup_Test = scanIdData.Dup_Test;
            locState = scanIdData.State;
            locHair = scanIdData.Hair;
            locEndorsements = scanIdData.Endorsements;
            locZip = scanIdData.Zip;
            locHeight = scanIdData.Height;
            locFee = scanIdData.Fee;
            locCounty = scanIdData.County;
            locClass = scanIdData.Class;
            locRestriction = scanIdData.Restriction;
            locDateOfBirth = scanIdData.DateOfBirth;
            locSex = scanIdData.Sex;
            locSigNum = scanIdData.SigNum;
            locType = scanIdData.Type;
            locWeight = scanIdData.Weight;
            locAddress2 = scanIdData.Address2;
            locAddress3 = scanIdData.Address3;
            locAddress4 = scanIdData.Address4;
            locAddress5 = scanIdData.Address5;
            locText1 = scanIdData.Text1;
            locText2 = scanIdData.Text2;
            locText3 = scanIdData.Text3;
            Console.WriteLine("Data saved succesfully.");
        }

        #endregion
    }
}

编辑

我按照Onur的建议做了，是的， 阻止主UI线程的是全局变量scan Lib 。我运行了以下代码，它没有冻结主UI线程:

Task debugTask = Task.Run(() =>
        {
            // All 4 variables below are global and used extensively to call scanner methods
            // Main Scan basic functions Library
            NetScanW.SLibEx scanSlibxEx = new NetScanW.SLibEx();
            // Main Scan extended functios Library
            NetScanW.CImage scanCImage = new NetScanW.CImage();
            // Main Scan OCR functions library
            NetScanW.IdData scanIdData = new NetScanW.IdData();
            // Main Scan extended functions 2 library
            NetScanWex.SLibEx scanWexSlibxEx = new NetScanWex.SLibEx();
            string ImageSource = @"C:\Scans\";
            string currentScan = ImageSource + "MyScan.bmp";
            string modifiedScan = ImageSource + "MyEditedScan.bmp";
            InitScanLibraries(scanSlibxEx, scanIdData);
            ScanCard(currentScan, modifiedScan, scanSlibxEx);
        });

是的，它非常非常困惑，但是可以正常工作，并且没有冻结。我所做的只是声明全局变量，初始化库并在同一线程中运行扫描，当然，它没有冻结主UI线程，但这远非我想要的。我需要这些库保持初始化状态，并在辅助线程中运行，并且当我需要扫描某些内容时，让它从ScanLib引用变量中调用ScanLib方法，由于我不知道将其放置在何处，因此我仍然很困惑它不会阻止主UI线程。我将尝试以下Onur的答案，看看会发生什么。

最终编辑

为了最终确定我的问题，我想添加解决的代码，以防其他人需要它。根据Orun的回答，我没有在顶部声明全局变量(如ScanLib refScanLib = new ScanLib())，而是将它们声明为null对象，如下所示:ScanLib refScanLib = null，在Form构造函数中，我添加了一个新方法名为InitializeVariables()的操作如下:

public void InitializeVariables()
    {
        NetScanW.SLibEx scanSLibExx = null;
        NetScanW.IdData scanIdDataa = null;
        NetScanW.CImage scanCImagee = null;
        NetScanWex.SLibEx scanWexSLibExx = null;
        var th = new Thread(() => 
        {
            scanSLibExx = new NetScanW.SLibEx();
            scanIdDataa = new NetScanW.IdData();
            scanCImagee = new NetScanW.CImage();
            scanWexSLibExx = new NetScanWex.SLibEx();
        });
        th.SetApartmentState(ApartmentState.MTA);
        th.Start();
        th.Join();
        this.scanSlibxEx = scanSLibExx;
        this.scanIdData = scanIdDataa;
        this.scanCImage = scanCImagee;
        this.scanWexSlibxEx = scanWexSLibExx;
    }

在此之后，一切工作都很棒。我还没有完全理解它，但是它起作用了，谢谢大家的帮助。

Answer 1

在使用COM库时，这在类似情况下对我有用。

internal static class Program
{
    /// <summary>
    /// The main entry point for the application.
    /// </summary>
    [STAThread]            // <= I needed to add this attribute
    private static void Main()
    {
       //...
    }
}




public partial class MainForm : Form () 
{    
    // you can call this in the InitializeComponents() for instance
    void someMethodInYourFormIERunningOnTheUIThread()
    {
        ScanLib scanLib  = null;
        var th = new Thread(() =>
        {
            scanLib = new ScanLib();
        });
        th.SetApartmentState(ApartmentState.MTA); // <== this prevented binding the UI thread for some operations
        th.Start();
        th.Join();
        this.scanLibraryReference = scanLib;
    }
    //...
}