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I have a few lab domains that are not trusted with our primary domains, but through the IP or FQDN, I can still map from the non trusted domains with proper credentials.
My problem is that when I run a sessionmanager program I want, it fails when trying to query the hostname from the IP ... which it cannot do because of the broken trust.
I'm having trouble writing error checking for this so I can skip this part of the code, if the return value comes back as a socket error of "no such host found", does anyone have any ideas on how to code for this return value. An example of it failing would be
MessageBox.Show(Dns.GetHostEntry(session["ComputerName"].ToString()).HostName);
will give a return value of "No such host found" and also cause the program to bomb. Any help would be appreciated, thank you.
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Will this work?
string hostName = "No host found";
try {
IPHostEntry entry = Dns.GetHostEntry(session["ComputerName"].ToString());
if (entry != null) {
hostName = entry.HostName;
}
} catch (Exception e) {
}
modified on Thursday, August 11, 2011 6:57 AM
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Hi,
Thank you for the reply. That did work although the catch from your snippet still has "No such host found" and then it just continues on through the code. I've never done that before, but as long as that is ok I'm happy! 
Thank you.
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turbosupramk3 wrote: That did work although the catch from your snippet still has "No such host found" and then it just continues on through the code.
I did it on purpose. The only executable code within the try block is the call to the GetHostEntry method. If the method throws an exception, it still means that the host was not found.
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Great, I will use this technique from now on
Thanks again!
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This is one of those few cases where an empty catch is (at least arguably) appropriate. In general, anything where you're trying to look things up through an external service (in this case, DNS) and the default option is 'failure to find X', it's ok to do this, though if the exception provides extra information you should at least read its message.
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In a production app, I would log the exception and/or take a different course of action.
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Hello,
I am attempting to create a benchmarking software that reads the contents of files.
I would like to report, every five seconds, the average speed per MB read, the speed in MB/sec.
I don't think that calculating a TimeSpan will be the best method, as it will definitely be inaccurate overtime (increasing in inaccuracy).
If I use a timer in the BackgroundWorker thread, how do I pass a variable to the ElapsedEventHandler that contains the amount of data read?
private void timer_Elapsed(object sender, ElapsedEventArgs e)
{
MessageBox.Show(AmountOfBytesRead);
}
public void ReadFiles(string TargetDirectory, bool RecursivePlz, string LogFilename)
{
DateTime StartOfReading = DateTime.Now;
System.Timers.Timer timer = new System.Timers.Timer();
timer = new System.Timers.Timer();
timer.Elapsed += new ElapsedEventHandler(timer_Elapsed);
timer.Interval = 5000;
timer.Start();
...
}
Thanks,
Matt
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A BackgroundWorker can report progress... Turn on the WorkerSupportsProgress flag, cast the "sender" to a BackgroundWorker and use that to send a progress report. You're supposed to send the completion percentage as an integer, but you can also supply a "state" object along with that, which could contain the bytes read.
Now, if you want to get the amount of data read in the past X seconds, you need a rolling buffer... Maybe it could go something like this:
1) Every N bytes (Maybe every 500KB or so), the worker reports the bytes read as a progress event
2) The handler dumps that into a rolling buffer with a time stamp (DateTime), and maintains a pointer to the oldest record within the desired time span.
3) The speed is calculated as (BytesRead[current] - BytesRead[oldest]) / (TimeStamp[current] - TimeStamp[oldest]) and put into a class-level variable.
4) Every so often, your timer can just read that variable to report the speed (Or whatever you want to do with it)
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That's a great idea. I was thinking backward.
The concern is cross-thread communication, and I think you addressed this.
BackgroundWorker_ProgressChange() has access to the main thread, which includes all objects in the inclusive/root class, such as a class-wide variable to hold a value, and the Timer object and events.
I still have the problem of accuracy, "left over" bytes when polling occurs.
I'll get testing!
Thanks very much,
Matt
modified on Wednesday, August 10, 2011 11:33 AM
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bbranded wrote: I still have the problem of accuracy, "left over" bytes when polling occurs.
Not really, with the rolling buffer... You would keep the actual time of each report (You could even pass a DateTime+Integer struct from the worker to eliminate cross-thread delays), so you wouldn't have to make any assumptions... Your buffer would look something like:
11:37:50 1500KB
11:37:52 2000KB
...
11:42:30 58000KB
11:42:33 58500KB
So you would get:
(58500KB - 1500KB) / (11:42:33 - 11:37:50)
= 57000KB / 4:43
And I'm too lazy to calculate that out, but that'll give you a KB/minute for the past ~5 minutes. And of course you can adjust the numbers to get whatever level of precision you want. The timer wouldn't actually be used to do any measurements, but rather to just report the results.
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This is very far from perfect, but will give others a good starting point to address this issue.
I'll open source the final project over at mbrownnyc.wordpress.com shortly.
private void _bw_DoWork(object sender, DoWorkEventArgs e)
{
string[] CommandArguments = e.Argument.ToString().Split('#');
string TargetDirectory = CommandArguments[0];
bool RecursivePlz = Boolean.Parse(CommandArguments[1]);
string LogFilename = CommandArguments[2];
ReadFiles(TargetDirectory, RecursivePlz, LogFilename);
}
public void ReadFiles(string TargetDirectory, bool RecursivePlz, string LogFilename)
{
int readsize = 65536;
double ReadOpsPerMB = readsize / 1048576;
TargetDirectory = TargetDirectory.ToLower();
if (!TargetDirectory.Contains("dfsrprivate"))
{
if (Directory.Exists(TargetDirectory))
{
string[] FileList = Directory.GetFiles(TargetDirectory);
int BytesReadInRound = 0;
foreach (string ffile in FileList)
{
FileInfo finfo = new FileInfo(ffile);
if (finfo.Exists)
{
int SizeOfFile = Int32.Parse(finfo.Length.ToString());
FileStream readStream = new FileStream(ffile, FileMode.Open, FileAccess.Read, FileShare.None, readsize + 1);
BinaryReader binReader = new BinaryReader(readStream);
string Status = "";
bool Readthefile = true;
try
{
if (binReader.PeekChar() <= -1)
{
Status = "EMPTY;" + ffile;
_bw.ReportProgress(0, Status);
Readthefile = false;
}
}
catch (Exception e)
{
Readthefile = true;
_bw.ReportProgress(0, ffile + " caused an exception, but was added to the total count: " + e.Message);
}
if (Readthefile)
{
byte[] valuebytes;
bool donereading = false;
_bw.ReportProgress(0, "reading " + Decimal.Divide(SizeOfFile, 1024).ToString() + " file: " + ffile);
while (donereading == false)
{
DateTime StartOperationTime = DateTime.Now;
valuebytes = binReader.ReadBytes(readsize);
BytesReadInRound = BytesReadInRound + valuebytes.Length;
donereading = (valuebytes.Length < readsize);
if (BytesReadInRound >= 1048576)
{
_bw.ReportProgress(2, "read|" + BytesReadInRound + "|" + LogFilename + "|" + DateTime.Now);
BytesReadInRound = 0;
}
DateTime EndOperationTime = DateTime.Now;
TimeSpan OperationTime = EndOperationTime.Subtract(StartOperationTime);
}
}
readStream.Close();
readStream.Dispose();
binReader.Close();
}
}
string[] SubDirectorylist = Directory.GetDirectories(TargetDirectory);
Array.Reverse(SubDirectorylist);
if (RecursivePlz == true)
{
if (Directory.Exists(TargetDirectory))
{
foreach (string ddir in SubDirectorylist)
{
ReadFiles(ddir, RecursivePlz, LogFilename);
}
}
}
}
}
}
struct SnapshotData
{
public string What;
public int HowManyBytes;
public string LogFilename;
public DateTime When;
}
List<SnapshotData> SnapShots = new List<SnapshotData>();
private void _bw_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
string UserState = e.UserState.ToString();
if (UserState.Contains("|"))
{
string[] UserStateCommands = UserState.Split('|');
SnapshotData Snapshot = new SnapshotData();
Snapshot.What = UserStateCommands[0];
Snapshot.HowManyBytes = Convert.ToInt32(UserStateCommands[1]);
Snapshot.LogFilename = UserStateCommands[2];
Snapshot.When = Convert.ToDateTime(UserStateCommands[3]);
SnapShots.Add(Snapshot);
TimeSpan Snapshotdifference = Snapshot.When.Subtract(SnapShots[0].When);
textBox2.Text = Snapshotdifference.ToString();
if (Snapshotdifference.TotalSeconds >= 10)
{
decimal ReadAfterLastFlushToLog = new decimal();
foreach (SnapshotData member in SnapShots)
{
ReadAfterLastFlushToLog = (ReadAfterLastFlushToLog + member.HowManyBytes);
}
ReadAfterLastFlushToLog = Decimal.Divide(Decimal.Divide(Decimal.Divide(ReadAfterLastFlushToLog,60),1024),1024);
StreamWriter LogFileWriter = new StreamWriter(Snapshot.LogFilename, true);
textBox5.Text = DateTime.Now.ToString() + ";" + ReadAfterLastFlushToLog.ToString();
LogFileWriter.WriteLine(DateTime.Now.ToString() + ";" + ReadAfterLastFlushToLog.ToString());
LogFileWriter.Close();
textBox2.Text = "";
SnapShots.Clear();
}
}
modified on Monday, August 22, 2011 1:09 PM
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 my 5!
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bbranded wrote: I don't think that calculating a TimeSpan will be the best method, as
it will definitely be inaccurate overtime (increasing in inaccuracy).
Only if you do it wrong.
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Oh please please, share your wisdom. It's torture that you're keeping it all to yourself.
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What? Oh.
Well I suspect you're considering calculating TimeSpans and adding them together rather than keeping the beginning time and calculating the whole elapsed time.
I'd likely use a StopWatch anyway, but that's just me.
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Thanks. I'll look into that direction to solve the problem as well.
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Hi All !
I use this Syntax for Filtering LastName field :
string strFilter = "LastName like '" + txtFamily.Text + "%'";
dvShowTable = new DataView(dataconn.dSet.Tables["PersonTable"], "", "", DataViewRowState.OriginalRows);
dvShowTable.RowFilter = strFilter;
dgShowTable.DataSource = dvShowTable;
if (dvShowTable.Count == 0)
{
MessageBox.Show("No find any Record !");
txtFamily.Text = "";
return;
}
It's works , but another filtering is about Account Field and I use this Syntax :
string strFilterAccount = "AccountNo like '" + Convert.ToDouble(txtAccount.Text)+"%'";
I have this Error:
Cannot perform 'Like' operation on System.Double and System.String
And If i use this syntax :
string strFilterAccount = "AccountNo="+ Convert.ToDouble(txtAccount.Text);
mmediately i put any Number , you get the message in the "If" conditional .
what is suitable instead of Like for number Field !
thanks
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The LIKE operator is used only for string filtering, it cannot be used with numeric datatypes. You can try other operators like >= and <= etc.
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Check out this MSDN page on the filter: http://msdn.microsoft.com/en-us/library/system.data.datacolumn.expression.aspx[^]
One thing it says is that the % sign should be between brackets [ ].
Like doesn't work for the double, so that's why you are getting that error. You need to use the compare operators, such as =. You say that is not working? Try putting a space between AccountNo and =, so: string strFilterAccount = "AccountNo = " + Convert.ToDouble(txtAccount.Text);
I wonder though, is Double really the proper type for an AccountNo? AccountNo sounds more like an integer to me.
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MicroVirus wrote:
string strFilterAccount = "AccountNo = " + <br />
Convert.ToDouble(txtAccount.Text);
That shouldn't even compile, let alone work. Why convert to a Double whe you need a String for the filter...
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Course it will, double has a ToString method which will be called at the + 
Converting to a number and back is elementary validation, throwing an exception at that point rather than in the database query.
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Way cool. 
You mean I've been wasting keystrokes all this time actually putting in the .ToString() business?
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I believe conversion from double to string is a widening conversion and thus can be done implicitly.
Anyway, your point about the there and back again conversion is right. I was more focused on solving the stated problem than watching what I copy-pasted.
The input should be validated beforehand, but this there-and-back-again method does avoid some SQL injection-like vulnerabilities.
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Your code has SQL injection written all over it, though I'm not sure how protective the DataView is (i.e. whether it passes that filter through to any database level processor where it could do real damage). Even if it protects you in this instance, get into the habit of escaping anything you put in a query string (and that's what that filter string is).
I agree with MicroVirus that you probably want the account to be an int and use =. With double you can use int or you can use (AccountNo>=value-delta) AND (AccountNo<=value+delta) where delta is a comparison tolerance value which you should pick.
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