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IN my C# apps, I use ArrayList's to store many types of objects. Of course when I pull anything out of any ArrayList I have to employ a cast. For example:
ArrayList listOfStrings();
:
String myString = (String)listOfStrings[3];
I end of doing so much casting! Is that typical? Can I avoid all the casting? Or is there some fundamental technique using ArrayLists that I am missing?
Thanks!
Mark Mokris
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You want to create your own strong typed collection by deriving from System.Collections.CollectionBase class. Check the MSDN for CollectionBase to see how to implement this (override Add, Remove, this[] etc methods).
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I think the question was is there anything wrong with all of the casting.
I also employ the arraylist for the same purpose, so I'd like to hear from the C# gurus too.
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Well, generics will help if you're using VS 2005, but with the current version, you're stuck with the cast or using the as syntax.
Of course if you are iterating over the items in an ArrayList, you can use foreach and that is nicer.
foreach( string s in arrayListOfStrings )
Console.WriteLine( "The list contains {0}", s );
Matt Gerrans
-- modified at 22:59 Thursday 25th August, 2005
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It depends on what types of objects you are inserting in the ArrayList. If you are inserting reference types (basically any object) there's a very slight, almost negligible, performance penalty in casting to and from object.
On the other hand, if you insert value types (ints, doubles, DateTimes and so on) in the ArrayList, the performance penalty is big because when you put a value type in an object variable, the compiler has to create a dummy object to contain the value and insert a reference to that object (a process called boxing). When you cast an object to a value type (when getting an item from the ArrayList for example) the process is called unboxing and is the exact opposite: go get the object and take the value from inside it.
An advantage of using specialized collections derived from CollectionBase is that the compiler does type checking for you. You usually can't assign an object to a typed variable without casting, but the other way around is not true: you can assign a variable of any type to a object variable. With a specialized collection, you can't add items of other types without the compiler complaining.
-- LuisR
Luis Alonso Ramos
Intelectix - Chihuahua, Mexico
Not much here: My CP Blog!
The amount of sleep the average person needs is five more minutes. -- Vikram A Punathambekar, Aug. 11, 2005
-- modified at 23:13 Thursday 25th August, 2005
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My experience is adding objects with the same type to one arraylist.
if casting is needed, for instance, to a string array. you can use this statement:
string[] myString = ( string[] )listOfStrings.toArray( typeof(string ));
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A have C# application which is required to do a specific task
on a scheduled basis..i.e. may be once a day ,twice or thrice daily...
The application needs to be up all time and reads a scheduled timings information through a DB table and updates its scheduled time settings accordingly..
Any idea how to implement a simple customizable scheduler for this which
can reconfigure it self for the schedule and runs ,calls the specified funtion
that does the job...
Thanks in advance
Mohit
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Windows Service is the right way to go. All you need to do is having a Time ticker which will control when you want the specific methods to get executed.
Check this out
http://www.codeproject.com/csharp/CSharpWindowsServiceInst.asp
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Hello,
I want to subclass the list box of a dropdown combobox. I already have the Win32 handle of the list box, but how can I subclass it so I use a ListBox-derived class I have to handle its events and messages?
-- LuisR
Luis Alonso Ramos
Intelectix - Chihuahua, Mexico
Not much here: My CP Blog!
The amount of sleep the average person needs is five more minutes. -- Vikram A Punathambekar, Aug. 11, 2005
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I'll take a look into it... thanks!
-- LuisR
Luis Alonso Ramos
Intelectix - Chihuahua, Mexico
Not much here: My CP Blog!
The amount of sleep the average person needs is five more minutes. -- Vikram A Punathambekar, Aug. 11, 2005
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Hello,
I'm extending a ListBox with tooltips for items that don't fit, but I can't find out how to position the tooltip exactly over the item. I already got the item coordinates, but how do I tell the tooltip where to appear. It is possible via a Windows message, but how do I get the Win32 handle of the window?
[EDIT: There's a private Handle property... it could help]
Any other ideas?
-- LuisR
Luis Alonso Ramos
Intelectix - Chihuahua, Mexico
Not much here: My CP Blog!
The amount of sleep the average person needs is five more minutes. -- Vikram A Punathambekar, Aug. 11, 2005
-- modifed at 16:00 Thursday 25th August, 2005
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I guess this is all you need. Give me a candy if this works for you.
private void ListControlMouseMove(object sender, MouseEventArgs e)
{
Point ptOnlist = Point.Empty;
ListViewItem item = null;
int subItemIndex = -1;
int subItemTextWidth = -1;
ListViewItem.ListViewSubItem curSubItem = null;
if (e.Button == MouseButtons.None)
{
item = this.GetItemAt(e.X, e.Y);
if (item != null)
{
subItemIndex = this.GetSubItemIndexFromPoint(item, new Point(e.X, e.Y));
if (subItemIndex != -1)
{
curSubItem = item.SubItems[subItemIndex];
if (curSubItem != null)
{
if (curSubItem.Text.Length > 0)
{
subItemTextWidth = this.ListViewGetStringWidth(curSubItem.Text);
if (subItemTextWidth != -1)
{
subItemTextWidth += 12;
if (subItemTextWidth > this.Columns[subItemIndex].Width)
{
this.SetToolTipText(curSubItem.Text);
}
else
{
this.HideToolTip();
}
}
}
}
}
else
{
this.HideDynamicControls();
}
}
}
}
protected int GetSubItemIndexFromPoint(ListViewItem item, Point ptInList)
{
int sumOfWidths = 0;
int columnIndex = 0;
foreach (ColumnHeader column in this.Columns)
{
if (sumOfWidths < ptInList.X && ptInList.X < sumOfWidths + column.Width)
{
return columnIndex;
}
sumOfWidths += column.Width;
columnIndex++;
}
return -1;
}
private const int LVM_GETSTRINGWIDTHW = 4183
protected int ListViewGetStringWidth(string subItemText)
{
IntPtr hString = Marshal.StringToHGlobalAuto(subItemText);
int width = UnsafeNativeMethods.SendMessage(this.Handle, LVM_GETSTRINGWIDTHW, 0, hString);
Marshal.FreeHGlobal(hString);
return width;
}
protected void SetToolTipText(string toolTipText)
{
if (toolTipText != null)
{
this.toolTip.Active = true;
this.toolTip.SetToolTip(this, toolTipText);
}
}
Cheers.
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Sorry. It won't work. As matter of fact I'm using a ListBox, not a ListView, so all the above code doesn't really aply. But I appreciate your effort! Thanks! 
I found out using .NET Reflector that the ToolTip class uses "normal" tooltips (using TTM_ACTIVATE to make it active.) There's a special type of tool tips, called "tracking" that have the TTF_TRACK flag, and you activate them with TTM_TRACKACTIVATE, and set their position with TTM_TRACKPOSITION (all of them Win32 window messages). Tracking tooltips don't move with the mouse; they just stay where they appear.
So I guess I'll have to rewrite the entire ToolTip class into something like TrackingToolTip. It doesn't really seem that hard to do, it's a simple class. I'll be sure to post an article here when I'm done.
Thanks!
-- LuisR
Luis Alonso Ramos
Intelectix - Chihuahua, Mexico
Not much here: My CP Blog!
The amount of sleep the average person needs is five more minutes. -- Vikram A Punathambekar, Aug. 11, 2005
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I hope the following works for you. As faar as ListBox is concerned you can do the following
[DllImport("user32.dll")]
public static extern IntPtr GetDC(IntPtr hWnd);
[StructLayout(LayoutKind.Sequential)]
public struct POINT
{
public int cx;
public int cy;
}
[DllImport("gdi32.dll")]
public static extern int GetTextExtentPoint32(IntPtr hdc, String str, int len, ref POINT pt);
[DllImport("user32.dll")]
public static extern int ReleaseDC(IntPtr hWnd,IntPtr hdc);
private void listBox1_MouseMove(object sender, System.Windows.Forms.MouseEventArgs e)
{
int index = this.listBox1.IndexFromPoint(e.X,e.Y);
if ( index > 0 )
{
IntPtr dc = GetDC(this.listBox1.Handle);
POINT pt;
pt.cx = 0;
pt.cy = 0;
GetTextExtentPoint32(dc, this.listBox1.Items[index].ToString() ,this.listBox1.Items[index].ToString().Length,ref pt);
ReleaseDC(this.listBox1.Handle, dc);
if(this.listBox1.Width < pt.cx)
{
this.SetToolTipText(this.listBox1.Items[index].ToString());
}
}
}
and as far as ToolTip is concerned
///
/// Set the position of the control with respect to the anchor control
///
/// <param name="anchorControl" />
private void SetPosition(Control anchorControl)
{
//
//Resolve the Balloon Coordinates
//to the client area
//
UnsafeNativeMethods.GetClientRect(anchorControl.Handle, ref this.toolInfo.rect);
UnsafeNativeMethods.ClientToScreen(anchorControl.Handle, ref this.toolInfo.rect);
//
//set the position of the toolTip to be
//displayed
//
int pt = MAKELONG(toolInfo.rect.left, toolInfo.rect.top + toolInfo.rect.bottom);
IntPtr ptr = new IntPtr(pt);
UnsafeNativeMethods.SendMessage(
this.Handle, TTM_TRACKPOSITION,
0, ptr);
}
[DllImport("User32", SetLastError = true)]
public static extern int GetClientRect(IntPtr hWnd, ref Rect lpRect);
[DllImport("User32", SetLastError = true)]
public static extern int ClientToScreen(IntPtr hWnd, ref Rect lpRect);
private const int WM_USER = 0x0400;
private const int TTM_TRACKACTIVATE = WM_USER + 17;
private int MAKELONG(int loWord, int hiWord)
{
return (hiWord << 16) | (loWord & 0xffff);
}
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That looks more like what I need... I'll try that code and get back to you. Did you test it?
-- LuisR
Luis Alonso Ramos
Intelectix - Chihuahua, Mexico
Not much here: My CP Blog!
The amount of sleep the average person needs is five more minutes. -- Vikram A Punathambekar, Aug. 11, 2005
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Yes I did. If you want I can send you the zipped project.
Live Life King Size
Alomgir Miah
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Well, sure! I was thinking of trying it monday morning when I get to the office, but if you can send it to me before that, I'll appreciate it! Thank you very much, really!
I won't post my e-mail here for spam reasons, but you'll find my e-mail on the notification message you get telling you I responded to your post.
-- LuisR
Luis Alonso Ramos
Intelectix - Chihuahua, Mexico
Not much here: My CP Blog!
The amount of sleep the average person needs is five more minutes. -- Vikram A Punathambekar, Aug. 11, 2005
-- modified at 4:09 Saturday 27th August, 2005
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Hi I need to make the way a child form pop up when I run my project.It contains information about my program and its the first form that should be seen>Anybody can tell mr how can I manage it?
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On the OnLoad event of the parent form do the following.
private void OnFormLoad(object sender, System.EventArgs e)
{
ChildForm f = new ChildForm();
f.MdiParent = this;
f.Show();
}
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Does it work?
In your way, you have to set this.isMdiParent = true;
Then its appearance will change. I do not think it is a good method.
ps: can you give me some idea to make a logo. many thanks!
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Hello again 
I'm currently developing a simple IRC client and right now I have to decide whether to use Regex or normal String methods to parse the incoming data. The incoming data looks like this and has to be parsed serveral times a second in frequently used IRC channels:
:Nicky!u001@s1.bouncer.ca PRIVMSG #asdf :Hello everybody :)
This is my code - it works and is easy to maintain, but how fast is it compared to using String methods like IndexOf(), Substring() etc?
string pattern1 = @"^:(?<nick>.+)!(?<user>.+)@(?<hostname>[^\s]+)\s(?<command>\w+)\s(?<channel>.+)\s:(?<text>.+)$";
MatchCollection mc = Regex.Matches(cmd, pattern1);
if(mc.Count > 0)
{
for(int i=0; i<mc.Count; i++)
{
GroupCollection gc = mc[i].Groups;
if(gc.Count >= 6)
{
nick = gc[1].Value;
user = gc[2].Value;
host = gc[3].Value;
cmd = gc[4].Value;
channel = gc[5].Value;
text = gc[6].Value;
}
}
}
modified 12-Sep-18 21:01pm.
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String size: how big is the string? If it's only a few chars, IndexOf is faster. If it's a few KB, Regex can be several times faster.
Don't forget to create compiled Regexes.
I see dead pixels
Yes, even I am blogging now!
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