Problem in Code : SEE COMMENT** - C# Discussion Boards

Hi!
This won't work because ping uses ICMP echo request packages, not TCP connections to check for connectivity.
(Btw. you don't even have to try UDPClient, this won't work either.:->)

If you want the code for a real ping, take a look here[^]

Otherwise, you could try to connect to the real server object you're trying to use later on to check whether it exists and is reachable.

Regards,
mav

thank you,

i do try catch later for the remoting but at startup, the client doesnt know about any servers.

is it possible to broadcast for remoting servers? i am trying this at the moment ?

if i cant get it i will try your ping link and see how i go.

thank you for response

g00fy

simple, i used this

<br />
internal void CheckLANConnectivity()<br />
    {<br />
      this.initLabel.Text = "Checking Network Connectivity ... ";<br />
      this.Refresh();<br />
      <br />
      // get host to check from app.config file<br />
      string host = System.Configuration.ConfigurationSettings.AppSettings["host"];<br />
      Debug.WriteLine("host from config file: " + host);<br />
      <br />
      IPHostEntry serverHE;<br />
      try<br />
      {<br />
        serverHE = Dns.GetHostByName(host);	<br />
        this.initLabel.Text = "Network Connectivity ... PASS ";<br />
        Debug.WriteLine("hostbyname: " + serverHE.ToString());<br />
      }<br />
      catch(Exception)<br />
      {<br />
        this.initLabel.Text = "Network Connectivity ... FAIL ";<br />
      }<br />
    }<br />

simple but works, just need to know its there

kind regards,
g00fy

Careful, here you only get the information that your DNS knows about a computer with the given name!
This doesn't mean the computer is running and reachable.

One way to check for a server (at least if you're in a LAN) could be to broadcast a UDP request on the subnet and have the server answer this request with information on how it's reachable.

Regards,
mav

yeah thanks mav,

i realised that after it failed on me once so i did exactly as you suggested Smile | :)

thanks again
g00fy

I am using following code to populate my windows datagrid. I have a boolean colunm for credit card transactions [called CCTransaction]. I would like this column to be a check box column insted of it showing 0s and 1s. Could you please help me with this. Thanks and advace.

private void frmEntryDataGrid_Load(object sender, System.EventArgs e)
{
    string sqlString    = "SELECT ID, CheckNumber, CCTransaction, Comments, Total, Amount, DateTimeVal FROM tbl_Total_Control";
    SqlDataAdapter da   = new SqlDataAdapter(sqlString, SqlConn);
    DataSet ds      = new DataSet();
    try
    {
        da.Fill(ds,"tbl_Total_Control");
        dgTC.DataSource = ds.Tables["tbl_Total_Control"];
    }
    catch(SqlException exSQL)
    {
        MessageBox.Show(this,exSQL.Message,"DATABASE ERROR!",MessageBoxButtons.OK,MessageBoxIcon.Error);
    }
    catch(Exception exc)
    {
        MessageBox.Show(this,exc.Message,"ERROR!",MessageBoxButtons.OK,MessageBoxIcon.Error);
    }
    finally
    {
        if(SqlConn.State == ConnectionState.Open)
        {
            SqlConn.Close();
        }
    }
}

use DataGridBoolColumn

See MSDN for details.

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlrfsystemwindowsformsdatagridboolcolumnclasstopic.asp

If someone could take a look at this code and see what I'm doing wrong I'd appreciate it. If I place the code that converts the TextBox values to cmplxValue1's //SEE COMMENT**1,**2, in the try block I get a
line from the (0,0) in the ClientRect, to the center of the ClientRect.
If I try to convert in the button click I get an unhandled exception.
//////////////////////////////////////////////////////////////////////////
** Exception Text **************
System.FormatException: Input string was not in a correct format.
at System.Number.ParseDouble(String s, NumberStyles style, NumberFormatInfo info)
at System.Double.Parse(String s, NumberStyles style, IFormatProvider provider)
at System.Convert.ToDouble(String value)
at ComplexTest2.Form1.DrawComplexNumber(Graphics g, Complex2 cmplxValue1) in c:\documents and settings\xyz\my documents\software engineering\c#_projects\c#_ tempfiles\complextest2\form1.cs:line 340
//////////////////////////////////////////////////////////////////////////

//code on Form1 linked to Complex2 class-> yes I hav Set/Get properties for all...
//Member fields.

public Pen[] activePen = new Pen[] { new Pen( Color.Blue ), new Pen( Color.Green ), new Pen(Color.Red) };
Complex2 c_xy = new Complex2(250, 250); //OK
protected Complex2 cmplxValue1 = new Complex2(0,0); //OK
protected Complex2 cmplxValue2 = new Complex2(0,0); //OK

private void Form1_Paint(object sender, System.Windows.Forms.PaintEventArgs e)
{
//Graphics g = this.CreateGraphics();
//Pen [] cmplxPen = new Pen []{new Pen(Color.Red, 2), new Pen(Color.Green, 2), new Pen(Color.Blue, 2)};
DrawGraphRectF(e.Graphics);//WORKS
DrawXYAxes(e.Graphics);//WORKS
DrawGraphXandYTicks(e.Graphics);WORKS
if(cmplxValue1.DrawLine1)//bool flag
//MessageBox.Show(Convert.ToString(xIndent + graphRect.Width/2)); //OK as Test for Runtime Values = 250, 250
DrawComplexNumber(e.Graphics, cmplxValue1);
}
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
private void complex_1OK_Click(object sender, System.EventArgs e)
{
//
try
{
/*bool flag*/cmplxValue1.DrawLine1 = true;
this.Invalidate();
}
catch
{
MessageBox.Show("Invalid Complex A Number", "Error!");
}
}
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
void DrawComplexNumber(Graphics g, Complex2 cmplxValue1)
{
this.cmplxValue1.Real = Convert.ToDouble(this.textComplex_1Real.Text); //SEE COMMENT ABOVE** 1
this.cmplxValue1.Imaginary = Convert.ToDouble(this.textComplex_1Imaginary.Text); //SEE COMMENT ABOVE **2
g.DrawLine(activePen[0], (float)c_xy.Real, (float)c_xy.Imaginary, (float)cmplxValue1.Real, (float)cmplxValue1.Imaginary);
}

"Input string was not in a correct format."

You are trying to convert a value that can not be interpreted as a number.

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b { font-weight: normal; }

Hi,

I have a control array and have tested the control type to find a listview. I want to assign the control to a listview with something like below.

System.Windows.Forms.ListView olistview = new ListView();
olistview = g_control_array[i];

C# does not like this and i get a cannot convert control to listview. Is there a way to achieve this as I can't find anything to help do this.

The only othe way I can think of is to establish an array of listviews as well but i would prefer not to do this unless I have to.

Thanks for any help.

Stephen

You want to read a ListView out of the control array?
Then you won't have to create a new one. The control array can contain any control, so you have to tell the compiler "I'm sure this item is a ListView":
ListView olistview;
olistview = (ListView)g_control_array[i];

Worked. Thanks.

Too easy!

Stephen

Hi I've got the following code:
I get the error: The node to be inserted is from a different document context.

I've already imported the, so whats wrong?

XmlNode toNode(string input)
{
XmlDocument a = new XmlDocument();
a.LoadXml(input);
return a.DocumentElement;
}

XmlNode tmp = toNode("<string></string>");
lines[linenumber].ImportNode(tmp, true);
lines[linenumber].AppendChild(tmp);
cheers

The ImportNode methods returns the node.

---
b { font-weight: normal; }

Howdy all,

I have a problem in trying to get application domains setup and hope somebody there could point me in the right direction. I came across code from gotdotnet that is called apploader (http://www.gotdotnet.com/Community/UserSamples/Details.aspx?SampleGuid=2C78AB99-E190-4A4A-A91A-F7DE1DE78E5B[^]. I am trying to implement a Windows Forms that creates an application domain, using the SpawnedApp class as per in the source for apploader, load the process into the newly created appdomain. Funny thing is this, in the AppLoader as per gotdotnet.com it's Main Thread attribute is [MTAThread], Winforms are by default [STAThread], Apploader worked a treat - loaded assemblies fine and worked, but I've tried to get it to work under winforms which fails. It loads the assemblies under the newly created appdomain on a winform and executes up to a certain point then it crashes. Is there something I'm missing or something that is not well documented regarding creating app domains in a winforms application?? Would threading have anything to do with it as that's my hunch. I click on a button which fires a thread, then creating a new instance of spawnedapp class with the full path to the assemblies/config file which in turn creates a thread and executes it in the new appdomain.

I've been tearing my hair out in frustration Big Grin | :-D

.Maybe my sig sums it all up!! Smile | :)

Hope you could help me out on this one!

Kind regards,
Tom Brennan.

#define STOOPID
#if STOOPID
Console.WriteLine("I'm stoopid!");
#endif

What code is failing?

- Nick Parker
Microsoft MVP - Visual C#
My Blog | My Articles

Hi Nick, Tom here, I have an application that has a lot of assemblies, and from the console AppLoader, it loads all the assemblies fine. It is from a WinForm Application that it loads partial assemblies then it keels over and dies with threadabort exception...The reason I wish to load it into an app domain is one of security. I was using the SpawnedApp Class from the AppLoader...

Thanks Nick for your reply! Smile | :)

Tom Brennan.

#define STOOPID
#if STOOPID
Console.WriteLine("I'm stoopid!");
#endif

Hi again Nick, Sorry for not replying sooner. This is interesting, the reason the Winforms that instantiated the class SpawnedApp in a new application domain failed was becuase I had an Application Wide Exception Handler for trapping unhandled exceptions. I removed the offending line and it worked. Strange!! WTF | :WTF:

That was the thing I noticed with the AppLoader code - it didn't have the application wide exception handler so I'm wondering why? Roll eyes | :rolleyes:

AppDomain didn't obviously like it and no wonder it keeled over and died upon loading the app in that new appdomain. So take this tip if you're having problems with AppDomains....Am currently investigating in the MS-KB to see if that's a documented behaviour or a bug..... Smile | :)

Thanks again Nick for your help!
Kind Regards,
Tom Brennan. Big Grin | :-D

#define STOOPID
#if STOOPID
Console.WriteLine("I'm stoopid!");
#endif

Hi fellows

I'm studying C# and I've seen the StructLayoutAttribute class. In their description was written this:
"The StructLayoutAttribute class allows the user to control the physical layout of data fields of a class or structure".
I've seen the LayoutKind enumerator too. This was written in their description: "Control the layout of an object when exporting to unmanaged code".
There are three options:
Auto, which the runtime chooses the appropriate layout for the members of an object.
Explicit: which the precise position ( Confused | :confused:

how? precise position?) of each member of object in unmanaged memory is controlled.
Sequential: which the members of object are laid out sequentially, in order that they appear whn exported to unmanaged code.

I didn't understand nothing. What want it to say when it says "control the physical layout" of a class?

Thanks for help guys

That is where each member is placed in the memory area that is reserved for the object or structure.

AFAIK, by default the members are arranged for fastest memory access, e.g. padded to place them on an even address boundary.

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b { font-weight: normal; }

hello,
Can anyone recommend one or two C# articles on CodeProject which you think has very good/professional code, is well-documented, uses good design, follows .NET coding guidelines, etc.

I'm looking for some examples of well written and complete classes/controls/etc that I can learn from to improve my own code.

Search for Marc Clifton's articles. Sometimes it can be confused in the beginning cause Marc understand a lot of C#, but if you read paying attention, the Marc's articles are great. There are a lot of great article writers, I prefer Marc.
Another good article writer is Xiangyang Liu.
I like of their styles, they are very professional in their articles. It's my opinion.

Thanks Alex,
I'll take a look at those articles...

Hi,

Please clarify which is more efficient.

using string.Empty or "". If so please explain why is this.
Iam often getting confused on this.

Thanks.

Hi!
Using "" will be marginally faster because the runtime doesn't have to look up a constant, but I strongly doubt that you will notice a difference in real life.

But I think it's more important to keep an eye on good readability than to try and tune execution speed by replacing string.Empty with "".

Regards,
mav