Question

我正在尝试将数据加载到组合框，并且在我运行表单而不进行调试时它就可以正常工作。但是，当我尝试在调试模式下运行它时，出现错误：System.InvalidOperationException：“跨线程操作无效：控制'ResultBox'从不是在其上创建线程的线程访问。我怎样才能解决这个问题？而且顺便说一句，有一个后台工作人员在下载数据时会写消息。我在某处读到可以使用backgroundworker修复此问题。这是表单代码：

public Form1()
    {
        InitializeComponent();
        backgroundWorker1.WorkerReportsProgress = true;
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        backgroundWorker1.RunWorkerAsync();
    }

    private Task GetDataTask() {
        return Task.Factory.StartNew(() => {
            List<Result> results = new List<Result>();
            results = 
 GetResults.GetData("http://worldcup.sfg.io/teams/results/");
            foreach (var result in results)
            {
                ResultBox.Items.Add(result.Fifa_Code);
            }
        });
    }

    private void ResultBox_SelectedIndexChanged(object sender, EventArgs e)
    {

    }

    private void SaveTeam_Click(object sender, EventArgs e)
    {

    }

    private async void backgroundWorker1_DoWork(object sender, 
 DoWorkEventArgs e)
    {
        await GetDataTask();
    }

    private void backgroundWorker1_ProgressChanged(object sender, 
 ProgressChangedEventArgs e)
    {
        resultsLoadedLabel.Text = (e.ProgressPercentage.ToString() + "%");
    }

    private void backgroundWorker1_RunWorkerCompleted(object sender, 
 RunWorkerCompletedEventArgs e)
    {
        resultsLoadedLabel.Text = "Podaci učitani!";
    }

foreach内的这行代码获取异常：

ResultBox.Items.Add(result.Fifa_Code);

这是获取结果的类：

public class GetResults
{

    public static List<Result> GetData(string url) {
        var client = new RestClient();
        var request = new RestRequest(url, Method.GET);
        request.AddHeader("User-Agent", "Nothing");
        IRestResponse<List<Result>> results = client.Execute<List<Result>> 
   (request);
        return results.Data;
    }
}

Answer 1

如果要异步，则要一直异步。 RestSharp允许您进行异步调用

因此您可以重构对的数据访问

public class GetResults {

    public static async Task<List<Result>> GetDataAsync(string url) {
        var client = new RestClient();
        var request = new RestRequest(url, Method.GET);
        request.AddHeader("User-Agent", "Nothing");
        IRestResponse<List<Result>> results = await client.ExecuteTaskAsync<List<Result>>(request);
        return results.Data;
    }
}

接下来，由于表单加载是事件处理程序，因此您也可以使该异步并加载数据。

public Form1() {
    InitializeComponent();
}

private async void Form1_Load(object sender, EventArgs e) {
    //On UI thread
    resultsLoadedLabel.Text = "Loading data!";
    //get data on separate thread (non blocking)
    List<Result> results = await GetResults.GetDataAsync("http://worldcup.sfg.io/teams/results/");
    //Back on UI thread
    resultsLoadedLabel.Text = "Podaci učitani!";
    foreach (var result in results) {
        ResultBox.Items.Add(result.Fifa_Code);
    }
}

确保在使用异步调用时访问UI控件时，可以在创建它们的主线程上访问它们，（请参见注释）。

foreach中的“跨线程操作无效”

1 个答案: