UPDATED With Improved Detail Source Code
Context: I am building a Winforms application using an MVC architecture. My View contains a Search Button, a ProgressBar, and BackgroundWorker control.
Events
this.wrkBackgroundSearch.WorkerReportsProgress = true;
this.wrkBackgroundSearch.WorkerSupportsCancellation = true;
this.wrkBackgroundSearch.DoWork += new System.ComponentModel.DoWorkEventHandler(this.wrkBackgroundSearch_DoWork);
this.wrkBackgroundSearch.RunWorkerCompleted += new System.ComponentModel.RunWorkerCompletedEventHandler(this.wrkBackgroundSearch_RunWorkerCompleted);
this.wrkBackgroundSearch.ProgressChanged += new System.ComponentModel.ProgressChangedEventHandler(this.wrkBackgroundSearch_ProgressChanged);
The BackgroundWorker (wrkBackgrounSearch)'s DoWork event:
private void wrkBackgroundSearch_DoWork(object sender, DoWorkEventArgs e)
{
BatchReaderController backgroundCnt = new BatchReaderController();
BackgroundWorker worker = sender as BackgroundWorker;
IDictionary<int, object> args = (IDictionary<int, object>)e.Argument;
//Breaking the arg list down
Int32 docType = (Int32)args[docTypeArgKey];
Int32 chosenSearchElement = (Int32)args[searchElementArgKey];
Int32 environment = (Int32)args[environmentArgKey];
try
{
e.Result = backgroundCnt.PerformSearch(docType, chosenSearchElement, environment, criteria, isFilenameSearch, worker, totalFileCount, directoriesToSearch, fileNameMask, xPath);
}
catch (Exception ex)
{
this.ShowError(ex.Message, "Error while searching", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}
I also have this event:
private void wrkBackgroundSearch_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
prgSearchProgress.Value = e.ProgressPercentage;
}
Finally, inside the custom BatchReaderController object's PerformSearch method I have PerformXPathSearch method. (This is the I/O-intensive operation that runs in the background, and is supposed to provide async updates.)
private IList<BatchFileData> PerformXPathSearch(IList<String> uncPaths, Int32 docType, Int32 searchElement, String searchCriteria, BackgroundWorker worker, Int64 totalFileCount, String inputFileMask, String inputXPathQuery)
{
Int64 numberFilesSearched = 0;
IList<BatchFileData> searchResults = new List<BatchFileData>();
//Validate inputs
//Look in each drive that was input
foreach (String networkPath in uncPaths)
{
DirectoryInfo dir;
FileInfo[] files = null;
try
{
dir = new DirectoryInfo(networkPath);
}
catch (Exception ae)
{
throw new Exception("Bad directory path: " + ae.Message, ae);
}
if (!dir.Exists)
{
continue;
}
try
{
files = dir.GetFiles(inputFileMask, SearchOption.TopDirectoryOnly);
}
catch (Exception ae)
{
throw new Exception("Invalid filename mask: " + filenameMask, ae);
}
foreach (FileInfo file in files)
{
numberFilesSearched++;
Boolean shouldOpenFile = DetermineWhetherToOpenFile(file.CreationTime);
XmlDocument xmlDoc;
XPathNavigator nav;
XPathNavigator searchNode;
DataSet xmlAsDataSet;
if (!shouldOpenFile)
{
Int32 percentComplete = CalculatePercentComplete(totalFileCount, numberFilesSearched);
worker.ReportProgress(percentComplete, searchResults.Count);
continue;
}
try
{
using (FileStream fs = file.OpenRead())
{
xmlDoc = new XmlDocument();
xmlDoc.Load(fs);
}
}
catch (UnauthorizedAccessException uae)
{
throw new UnauthorizedAccessException("Unable to read path to file: " + file.FullName, uae);
}
nav = xmlDoc.CreateNavigator();
try
{
searchNode = nav.SelectSingleNode(inputXPathQuery);
}
catch (ArgumentException ae)
{
throw new ArgumentException("Argument Exception performing node select: " + xpathQuery, ae);
}
catch (XPathException xpe)
{
throw new XPathException("Xpath error while performing node select: " + xpathQuery, xpe);
}
//If search results returns criteria success, add this data set to the list for display.
if (searchNode != null)
{
//Capture data for later processing
}
Int32 percentageComplete = CalculatePercentComplete(totalFileCount, numberFilesSearched);
worker.ReportProgress(percentageComplete, searchResults.Count);
}
}
return searchResults;
}
Calculate Percent Complete
private Int32 CalculatePercentComplete(Int64 totalFileCount, Int64 numFoldersSearched)
{
Int32 percentAsInt;
float searchPercent;
searchPercent = numFoldersSearched / totalFileCount;
try
{
percentAsInt = Convert.ToInt32(searchPercent);
}
catch (OverflowException oe)
{
throw new OverflowException("Error getting percent complete: " + oe.Message, oe);
}
if ((percentAsInt < 0) || (percentAsInt > 100))
{
throw new ArithmeticException("Invalid percentage: " + percentAsInt);
}
return percentAsInt;
}
Problem: When testing, my ProgressBar does not receive the updates, even though while stepping through the code, the ProgressChanged event IS being fired.
I have also tried several iterations of the following, after checking threads on StackOverflow, within the ProgressChanged event:
private void wrkBackgroundSearch_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
prgSearchProgress.Invoke(new PerformProgrssUpdate(this.DisplaySearchProgress),
new object[]{e.ProgressPercentage});
//if (prgSearchProgress.InvokeRequired)
//{
// prgSearchProgress.Invoke();
//}
}
private void DisplaySearchProgress(Int32 percentComplete)
{
prgSearchProgress.Value = percentComplete;
}
public delegate void PerformProgrssUpdate(Int32 percentComplete);
Note the commented-out attempt of another solution. The search operation will complete successfully, and when the search operation is completed, the ProgressBar control has its value updated to (1/n)% complete, as the search finishes.
Question How do I make this work, such that when my Controller performs the I/O-intense search, the Progress Bar in my view is updated appropriately, so that the user knows some function is being executed?
