C#使用后臺進程

C#使用多線程，推薦使用BackgroundWorker。

1、定義：

BackgroundWorker BgWorker = new BackgroundWorker();

2、初始化：

BgWorker.WorkerReportsProgress = true;  
BgWorker.DoWork += BgWorker_DoWork;    
BgWorker.ProgressChanged += BgWorker_ProgressChanged;    
BgWorker.RunWorkerCompleted += BgWorker_RunWorkerCompleted;

其中DoWork是線程要執行的函數。

ProgressChanged 是進度更新時的回調函數

RunWorkerCompleted 是線程執行完成時的回調函數，這個函數里面可以直接調用UI線程的東西。

注意：不可以把BackgroundWorker的DoWork等接口進行多次賦值，否則會造成目標函數被多次調用的問題。正確的做法是，每次需要重新賦值的時候，都進行BgWorker = new BackgroundWorker()操作。

3、函數體實現：

void BgWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)  
{    
    int progress = e.ProgressPercentage;

    LabelProgress.Text = string.Format("完成{0}%", progress);  
    LabelProgress.Left = (this.Width - LabelProgress.Width) / 2;    
}

void BgWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)  
{    
    if (PictureList.Count > 0)    
    {    
        ShowPicture(curIndex);    
    }    
    LabelProgress.Visible = false;    
}

void BgWorker_DoWork(object sender, DoWorkEventArgs e)  
{    
    List<string> picList = new List<string>();    
    string[] extList = { ".jpg", ".png" };    
    int index = 0;    
    foreach (string item in fileList)    
    {    
        if (extList.Contains(System.IO.Path.GetExtension(item).ToLower()) == true)    
        {    
            string backName = AddImageToDB(item);    
            Debug.WriteLine("ImageName:" + backName);    
            if (string.IsNullOrEmpty(backName) == false)    
                picList.Add(backName);    
        }    
        index++;    
        BgWorker.ReportProgress(100 * index / fileList.Count);    
    }    
    curIndex = PictureList.Count;    
    PictureList.AddRange(picList);    
}