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Yes it's possible, which is why the related methods are called AddMessageFilter and RemoveMessageFilter. There is a reason to keep a consistent naming convention, and Microsoft has done that with 90% of their code.
You also could've just thrown together a quick example. Throwing together samples is a staple of development.
Microsoft MVP, Visual C#
My Articles
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Sorry for the delayed response... been busy with school.
I had written an example, but it did not work. I have two instances of a class that each create their own controller (which derives from IMessageFilter) and passes it to Application.AddMessageFilter. However, only one of the controllers' PreFilterMessage functions is capturing input. The second one is never called. This is why I was wondering if it was possible to have two since it only seems to be working with one.
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Works fine for me. Internally, when you add an IMessageFilter implementation it gets added to an ArrayList, so it doesn't even matter if you add the same instance more than once. If you return true from your PreFilterMessage method (not "function", objects have "methods", btw), then the message does not get dispatched. I looked quickly and didn't find whether or not it is sent to remaining message filters or not right away. More than likely it is.
If you want, verify that things are working with my little test app which adds three message filters, 2 in the static entry point and another in one of the constructors, which makes 2 filters added using the same instance of a class:
using System;
using System.Windows.Forms;
public class Test : Form, IMessageFilter
{
static void Main()
{
Test t = new Test();
Application.AddMessageFilter(t);
Application.AddMessageFilter(new MessageFilter());
Application.Run(t);
}
public Test()
{
Application.AddMessageFilter(this);
Text = "Test";
}
public bool PreFilterMessage(ref Message m)
{
Print(this, m);
return false;
}
internal static void Print(object obj, Message m)
{
Console.WriteLine("[{0}] 0x{1:x2} -> 0x{2:x2}",
obj.GetType().Name, m.Msg, m.HWnd);
}
}
public class MessageFilter : IMessageFilter
{
public bool PreFilterMessage(ref Message m)
{
Test.Print(this, m);
return false;
}
}Like me, you should get three lines with each message sent to the application pump, like so:
[Test] Message.Msg -> Message.HWnd
[MessageFilter] Message.Msg -> Message.HWnd
[Test] Message.Msg -> Message.HWnd
Microsoft MVP, Visual C#
My Articles
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Yep, found the problem within seconds of reading your email. I was returning true and the message was not making it any further. Duh. Thanks so much for the help, this is all a lot clearer to me now.
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Hi all,
I have a datagrid populated from an XML file like the following:
<?xml version="1.0" standalone="yes"?>
<pairs xmlns="http://tempuri.org/Data.xsd">
<pair>
<x>3</x>
<y>10</y>
</pair>
<pair>
<x>4</x>
<y>17</y>
</pair>
...
</pairs>
and would like to convert this to a string of the values like this:
3 10 4 17 ...
(to create input for an old C++ app, just the values in one long string - nothing but numbers and spaces)
I hoped this would be fairly straightforward, but I haven't found how to do it.
(I could transform the XML file if necessary)
Any help much appreciated.
---
J
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With the below XML, I wrote this quick method to return a string value as you have requested.
<?xml version="1.0" standalone="yes"?>
<pairs>
<pair>
<x>3</x>
<y>10</y>
</pair>
<pair>
<x>4</x>
<y>17</y>
</pair>
</pairs>
private string GetInput()
{
XmlDocument doc = new XmlDocument();
StringBuilder sb = new StringBuilder();
XmlNode buffer = null;
doc.Load("../../data.xml");
XmlNodeList nodes = doc.SelectNodes("//pairs/pair");
if(nodes != null)
{
foreach(XmlNode node in nodes)
{
buffer = node.SelectSingleNode("x");
if(buffer != null)
sb.Append(buffer.InnerXml + " ");
buffer = node.SelectSingleNode("y");
if(buffer != null)
sb.Append(buffer.InnerXml + " ");
}
}
return(sb.ToString());
}
- Nick Parker
My Blog | My Articles
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excellent, thank you.
hadn't come across string builder before, am sure it will be useful.
---
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It's very useful - especially when formatting unknown lengths of strings. The String class is immutable - any changes to it force another string to be created and the chars within the original string to be copied to the new string merged with the changes you've made. Do this several hundred times and you're app is slow. The StringBuilder is a mutable string and eliminates these problems and should be used when appending strings like Nick pointed out. The StringBuilder is also used internally in many methods like String.Format.
Microsoft MVP, Visual C#
My Articles
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I get dates in the following format:
Mar-07 13:45
How can I feed this to a ConvertTo.DateTime expression without getting an exception?
Sammy
"A good friend, is like a good book: the inside is better than the cover..."
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Tough luck. I think you need to write your own function to read it and convert it to ISO format.
Check if the format is always mmm-dd hh:nn. If it is, it will be simpler for you to write the function.
I might be wrong though, so if anyone knows about this, feel free to answer. 
Edbert P.
Sydney, Australia.
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Yes in fact, it is always in this format.
How should I write this function?
Sammy
"A good friend, is like a good book: the inside is better than the cover..."
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I've checked that in your case you only need to add the year value to the string.
Here's what I would do:
string dateValue = "Mar-07 13:45";
string[] dateParts = dateValue.Split(' ');
dateValue = String.Concat(dateParts[0], "-", DateTime.Now.Year, " ", dateParts[1]);
You can use the final string as input for any DateTime functions.
Edbert P.
Sydney, Australia.
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A word of warning when reading December's data in January - it may have wrong year!
Remember to add logic something like pseudocode:
if(Month(data) > Month(Now))
DataYear -= 1;
Regards
Brewman
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Is it possible to add events to each cell of a Datagrid? For eg., I have a datagrid where I want to trigger something when the user navigates to row 3, cell 2. How do I do that?
Thanks
Al
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private void grid1_MouseUp(object sender, System.Windows.Forms.MouseEventArgs e)
{
DataGrid dg = (DataGrid)sender;
System.Drawing.Point pt = new Point(e.X, e.Y);
DataGrid.HitTestInfo hti = dg.HitTest(pt);
if(hti.Type == DataGrid.HitTestType.Cell)
{
if(hti.Row ==2 && hti.Column==3)
{
//do something
}
}
}
You can get HitTestInfo, and check if Hit Type is CELL (not row header/column header), and then get the corresponding ROW & COLUMN information.
Hope this help
Ruchi
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Hi Ruchi,
Thanks for the info! I was thinking more in terms of events like "When cursor leaves cell", "when cursor enters cell" etc. Do you know if that is possible with C# Datagrids?
Thanks
Al
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In C++ you can do something like this:
MyClass * myClass = new MyClass(a, b, c);
...
...
mySocket->Send(myClass, sizeof(MyClass));
when receiving:
BYTE buf[MAX_SIZE];
mySocket->Receive(&buf, sizeof(MyClass));
myClass = (MyClass *) &buf;
In other words, given an instance of a class or structure you can send/receive it over tcp/ip as a binary object without having to do any special coding or serialization.
How do I achieve the same thing in C#? I have a C++ based server that I want to communicate with using a C# front-end. The C++ server sends and receives structures. How can I convert a C# class or structure into raw bytes and send it over the network. The networking examples that I’ve been able to find all use strings, which are simple to convert to a series of bytes. I have not been able to find a single C# networking example that sends objects or structures over the network.
Any help from someone who has solved this issue (without serialization) would be greatly appreciated.
Thanks
Robert
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With Marshal.StructureToPtr you can convert your managed object to an unmanaged block of memory. Marshal.ReadByte can read the unmanaged object byte-by-byte into an array, so that you have a copy of the managed object in an array of bytes:
<br />
IntPtr newPointer = Marshal.AllocHGlobal( Marshal.SizeOf(yourObject) );<br />
Marshal.StructureToPtr( yourObject, newPointer, true );<br />
<br />
byte[] b = new byte[Marshal.SizeOf(yourObject)];<br />
<br />
for(int n=0; n<Marshal.SizeOf(yourObject); n++){<br />
b[n] = Marshal.ReadByte( newPointer, n );<br />
}
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Be careful when doing so, though. The managed class/struct must have exactly the same layout as your unmanaged class/struct. For classes and structures in .NET, you can use the StructLayoutAttribute to facilitate this when marshaling. Also pay close attention to unmanaged to managed types. For instance, a common mistake is that a LONG in C++ would be a long in .NET. Not true. The former is a 32-bit integer where the latter is a 64-bit integer.
Microsoft MVP, Visual C#
My Articles
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Thanks for the advise folks.
I am aware of the type differences between C++ and C#. So that would not be a problem for me. However, what about structure packing (i.e. #pragma pack(1))? Does StructLayoutAttribute ensure that the resulting structure in C# would be packed on the same boundaries as the C++ equivalent?
How about passing classes between a C# client and a C# server, is Remoting the best choice or should I use the same technique as passing structures between C# and C++ clients and servers?
I am most concerned about performance more than anything else because I am working on a stock trading application that needs to process huge amounts of streaming market data in real time.
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Read the documentation for the StructLayoutAttribute. It does have a Pack property which allows you to control the packing.
Remoting is basically serialization over transport channels and gives you the capability for aspect-oriented programming (inserting channel sinks to log calls, encrypt/decrypt messages, compress messages, and otherwise mangle messages). For talking to a legacy C++ socket listener, this wouldn't work. Remoting is best used between .NET applications but could - with a LOT of work - work between managed and unmanaged solutions. Web Services - for its greatly simplified interfaces - is better suited for legacy solutions.
When it comes to performance, marshaling the class/struct to a buffer would definitely be faster. Remoting and Web Services both require serialization. The .NET FCL provides both SOAP and binary formatters for serialization, the latter of which is MUCH faster than the former and uses less bandwidth (since SOAP - being yet another grammar derived from XML - has a lot of overhead).
Corinna's original idea I think is the right track, which is basically what you asked for.
Microsoft MVP, Visual C#
My Articles
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Thank you very much. That was very helpful.
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I have tried this successfully. But only with a class and struct that does not contain a string or byte array field. For example:
[StructLayout(LayoutKind.Sequential, Pack=1)]
public struct MyPacket
{
public MyPacket(DateTime dateTime, int line, int msgLen)
{
dt = DateTime.Now;
iLine = 0;
iMsgLen = 0;
msg = new byte[80];
}
public DateTime dt;
public int iLine;
public int iMsgLen;
public byte[] msg;
}
Marshal.Sizeof(MyPacket) returns 20. So when it is sent over the network I the contents of msg is lost. Obviously because byte[] is a reference to an array.
So, now the question is how can I pass classes or structures as binary data if they contain arrays, for example a message that contains a stock quote needs to include a symbol name (i.e. "MSFT").
Can you help me out with this as well? I have not been able to find any examples or documentation that shows StructLayout being used with structures or classes that contain strings or arrays.
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I have tried this successfully. But only with a class and struct that does not contain a string or byte array field. For example:
[StructLayout(LayoutKind.Sequential, Pack=1)]
public struct MyPacket
{
public MyPacket(DateTime dateTime, int line, int msgLen)
{
dt = DateTime.Now;
iLine = 0;
iMsgLen = 0;
msg = new byte[80];
}
public DateTime dt;
public int iLine;
public int iMsgLen;
public byte[] msg;
}
Marshal.Sizeof(MyPacket) returns 20. So when it is sent over the network I the contents of msg is lost. Obviously because byte[] is a reference to an array.
So, now the question is how can I pass classes or structures as binary data if they contain arrays, for example a message that contains a stock quote needs to include a symbol name (i.e. "MSFT").
Can you help me out with this as well? I have not been able to find any examples or documentation that shows StructLayout being used with structures or classes that contain strings or arrays.
By the way, what does Microsoft MVP mean? Are you a Most Valuable Player at Microsoft?
Thanks for the assistance,
Robert G. Ellis
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See the MarshalAsAttribute documentation. To make your implementation easier, use string instead of byte[] but be sure to marshal it as an ANSI string (since you're obviously using bytes for chars and not double-byte chars):
[StructLayout(LayoutKind.Sequential, Pack=1, CharSet=CharSet.Ansi)]
public struct Packet
{
public Packet(DateTime dt, int line, string msg)
{
if (msg == null) throw new ArgumentNullException("msg");
this.dt = dt;
this.line = line;
this.msglen = msg.Length;
this.msg = msg;
}
public DateTime dt;
public int line;
public int msglen;
[MarshalAs(UnmanagedType.LPStr)]public string msg;
}Now it's also possible that you may need to send a by-value string, in which case you use UnmanagedType.ByValTStr (it will be an ANSI string because of the CharSet property in the StructLayoutAttribute) and specify a constant size, which I know is often a valid limitation of chat software. This latter case is most likely what you'll need to do.
Also, keep in mind that the DateTime in .NET and whatever date/time struct/value you're using in C++ will most likely have different epochs. The DateTime struct uses 00:00:00 Jan 1, 0001 AD. Adjust your time as necessary. Often - depending on how your legacy solution is already coded, you should also use DateTime.ToUniversalTime or DateTime.UtcNow to use a UTC date which is based on zulu time (Greenwhich Mean Time). This ensures that your dates always have a common base. The clients use their locale information to get the local time.
goodpilot wrote:
By the way, what does Microsoft MVP mean? Are you a Most Valuable Player at Microsoft?
It means "Most Valuable Professional". You can read more about the program at http://mvp.support.microsoft.com[^].
Microsoft MVP, Visual C#
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