C# Discussion Boards - CodeProject

FocusedWolf15-Apr-05 11:23

15-Apr-05 11:23

string test = "1";
test.Replace("1","2");

i tried doing this in something more complex like cleaning out characters in a big string, but even after this code i'm seeing .net ignore me...test should equal "2" after this, and it doesn't.

Re: String.Replace...does it even work?

afinnell15-Apr-05 11:33

afinnell

15-Apr-05 11:33

Strings are immutable in .NET. This is for thread safety and other reasons. Do this instead

test = test.Replace("1", "2");

-
Drew

Re: String.Replace...does it even work?

FocusedWolf17-Apr-05 16:35

FocusedWolf

17-Apr-05 16:35

Wow little ackward but owell...Thx for clearing that up for me Smile | :)

Getting a DataSet of selected rows in a DataGrid

Member 141845415-Apr-05 10:47

Member 1418454

15-Apr-05 10:47

How can I get a dataset of selected rows in a DataGrid? It should get me the correct selected rows even if the grid is sorted on any one of the columns.

Re: Getting a DataSet of selected rows in a DataGrid

Member 141845425-Apr-05 6:13

Member 1418454

25-Apr-05 6:13

snnn wrote:
How can I get a dataset of selected rows in a DataGrid? It should get me the correct selected rows even if the grid is sorted on any one of the columns.

I am still looking forward for an answer. Would anyonr please help?

ListView and selectedindex changed event

code_wiz15-Apr-05 10:30

code_wiz

15-Apr-05 10:30

Hi,

We have this SelectedIndexChanged event that is raised by the .NET listview control.

I wonder why there is no SelectedIndexChanging event in the listview control. I have a need whereby i need to store the current index somewhere before the selectedindexchanged event is about to be raised. I can't see how i can achieve this. I certainly need an even that will tell me that the index is about to be changed. SelectedIndexChanged event is too late for me to store the index of the previously selected index.

Any ideas?

Re: ListView and selectedindex changed event

afinnell15-Apr-05 11:36

afinnell

15-Apr-05 11:36

It might seem logical that you could derive from the control and dispatch a pre notification event, but that might not work because the control just wraps the Win32 API. So your best bet is to keep a previousSelectedIndex around. When your SelectedIndexChanged delegate is invoked you can do what you need to do, then store the previousSelectedIndex at that time. The next time your delegate is invoked the previousSelectedIndex will be the previous index.

-
Drew

Communication with controls between classes

DJNokturnal15-Apr-05 10:11

DJNokturnal

15-Apr-05 10:11

Hey guys... first I just want to praise The Code Project and everyone on here for basically teaching me the basics of C#. I have a web background and this is the first language I have learned coming off my javascript and vbscript web knowledge.

I am sure this question has a very simple answer, but that is an answer I cannot figure out! Smile | :)

Here it is...

I have dummied down my problem into the following code examples. I have a very basic program that takes one richtext field and copies the content into another. I am doing so by calling a method in a separate class that accomplishes the copying of text.

Form1.cs:

<br />
using System;<br />
using System.Drawing;<br />
using System.Collections;<br />
using System.ComponentModel;<br />
using System.Windows.Forms;<br />
using System.Data;<br />
<br />
namespace TestApp<br />
{<br />
	/// <summary><br />
	/// Summary description for Form1.<br />
	/// </summary><br />
	public class Form1 : System.Windows.Forms.Form<br />
	{<br />
		private System.Windows.Forms.Label label1;<br />
		public System.Windows.Forms.RichTextBox txtFromSecondClass;<br />
		public System.Windows.Forms.RichTextBox txtToSecondClass;<br />
		private System.Windows.Forms.Label label2;<br />
		private System.Windows.Forms.Button button1;<br />
		/// <summary><br />
		/// Required designer variable.<br />
		/// </summary><br />
		private System.ComponentModel.Container components = null;<br />
<br />
		public Form1()<br />
		{<br />
			//<br />
			// Required for Windows Form Designer support<br />
			//<br />
			InitializeComponent();<br />
<br />
			//<br />
			// TODO: Add any constructor code after InitializeComponent call<br />
			//<br />
		}<br />
<br />
		/// <summary><br />
		/// Clean up any resources being used.<br />
		/// </summary><br />
		protected override void Dispose( bool disposing )<br />
		{<br />
			if( disposing )<br />
			{<br />
				if (components != null) <br />
				{<br />
					components.Dispose();<br />
				}<br />
			}<br />
			base.Dispose( disposing );<br />
		}<br />
<br />
		#region Windows Form Designer generated code<br />
		/// <summary><br />
		/// Required method for Designer support - do not modify<br />
		/// the contents of this method with the code editor.<br />
		/// </summary><br />
		private void InitializeComponent()<br />
		{<br />
			this.txtFromSecondClass = new System.Windows.Forms.RichTextBox();<br />
			this.label1 = new System.Windows.Forms.Label();<br />
			this.txtToSecondClass = new System.Windows.Forms.RichTextBox();<br />
			this.label2 = new System.Windows.Forms.Label();<br />
			this.button1 = new System.Windows.Forms.Button();<br />
			this.SuspendLayout();<br />
			// <br />
			// txtFromSecondClass<br />
			// <br />
			this.txtFromSecondClass.Location = new System.Drawing.Point(8, 200);<br />
			this.txtFromSecondClass.Name = "txtFromSecondClass";<br />
			this.txtFromSecondClass.Size = new System.Drawing.Size(280, 64);<br />
			this.txtFromSecondClass.TabIndex = 0;<br />
			this.txtFromSecondClass.Text = "";<br />
			// <br />
			// label1<br />
			// <br />
			this.label1.Location = new System.Drawing.Point(8, 176);<br />
			this.label1.Name = "label1";<br />
			this.label1.Size = new System.Drawing.Size(272, 16);<br />
			this.label1.TabIndex = 1;<br />
			this.label1.Text = "From SecondClass:";<br />
			// <br />
			// txtToSecondClass<br />
			// <br />
			this.txtToSecondClass.Location = new System.Drawing.Point(8, 32);<br />
			this.txtToSecondClass.Name = "txtToSecondClass";<br />
			this.txtToSecondClass.Size = new System.Drawing.Size(280, 64);<br />
			this.txtToSecondClass.TabIndex = 2;<br />
			this.txtToSecondClass.Text = "";<br />
			// <br />
			// label2<br />
			// <br />
			this.label2.Location = new System.Drawing.Point(8, 8);<br />
			this.label2.Name = "label2";<br />
			this.label2.Size = new System.Drawing.Size(272, 16);<br />
			this.label2.TabIndex = 3;<br />
			this.label2.Text = "Send To SecondClass:";<br />
			this.label2.Click += new System.EventHandler(this.label2_Click);<br />
			// <br />
			// button1<br />
			// <br />
			this.button1.Location = new System.Drawing.Point(24, 120);<br />
			this.button1.Name = "button1";<br />
			this.button1.Size = new System.Drawing.Size(240, 32);<br />
			this.button1.TabIndex = 4;<br />
			this.button1.Text = "Send To Second Class";<br />
			this.button1.Click += new System.EventHandler(this.button1_Click);<br />
			// <br />
			// Form1<br />
			// <br />
			this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);<br />
			this.ClientSize = new System.Drawing.Size(292, 273);<br />
			this.Controls.Add(this.button1);<br />
			this.Controls.Add(this.label2);<br />
			this.Controls.Add(this.txtToSecondClass);<br />
			this.Controls.Add(this.label1);<br />
			this.Controls.Add(this.txtFromSecondClass);<br />
			this.Name = "Form1";<br />
			this.Text = "Form1";<br />
			this.ResumeLayout(false);<br />
<br />
		}<br />
		#endregion<br />
<br />
		/// <summary><br />
		/// The main entry point for the application.<br />
		/// </summary><br />
		[STAThread]<br />
		static void Main() <br />
		{<br />
			Application.Run(new Form1());<br />
		}<br />
		private void button1_Click(object sender, System.EventArgs e)<br />
		{<br />
			SecondClass.transferText(txtToSecondClass.Text);<br />
		}<br />
<br />
		private void label2_Click(object sender, System.EventArgs e)<br />
		{<br />
		<br />
		}<br />
	}<br />
}<br />

SecondClass.cs:

<br />
using System;<br />
<br />
namespace TestApp<br />
{<br />
	/// <summary><br />
	/// Summary description for SecondClass.<br />
	/// </summary><br />
	public class SecondClass<br />
	{<br />
		public static void transferText(string x)<br />
		{<br />
			Form1 formObj = new Form1();<br />
			formObj.txtFromSecondClass.Text = x;<br />
		}<br />
	}<br />
}<br />

Any input would be awesome. Thanks again for such a great site =)

P.S. This isn't an example of the real code I am working on, but does illustrate the problem I have. I know the above project can be very simply accomplished in one class.

Re: Communication with controls between classes

Nicholas Cardi15-Apr-05 13:34

Nicholas Cardi

15-Apr-05 13:34

your problem is that you are creating a new instance of form1.

You need to pass in the existing instance of form1

transfertext to take the existing instance

public static string transfertext(System.Windows.Forms.Form x)
{
return x.txtFromSecondClass.Text;
}

usage

string value = SecondClass.transfertext(this);

best of luck

Forever Developing

Re: Communication with controls between classes

DJNokturnal15-Apr-05 13:54

DJNokturnal

15-Apr-05 13:54

Hey thanks for the reply!

... and here is the but hehehe ...

Can you treat me like a moron, and show me the rewritten methods for each class? I just can't wrap my mind around this...

Cry | :((

Re: Communication with controls between classes

DJNokturnal18-Apr-05 5:40

DJNokturnal

18-Apr-05 5:40

..\..\..\SecondClass.cs(12): 'System.Windows.Forms.Form' does not contain a definition for 'textFromSecondClass'

That is what I get when I try to use your code. I guess I have some reading to do.

Thanks anyway.

A list of pairs (string, int) + sorting

domo_15-Apr-05 10:00

domo_

15-Apr-05 10:00

Hi there,

I'm kind of new to C# (that might explain this question).

I stuck with my code when I have to:
1. implement a list of pairs (string, int)
2. sort it by int

Could you give me some hints on points 1 & 2?

Thanks

Domo_

Re: A list of pairs (string, int) + sorting

afinnell15-Apr-05 11:50

afinnell

15-Apr-05 11:50

The first step is to define a structure to hold your data. I used the property accessors in this case because it is part of my habit. These aren't required but are there for good measure.

The second step is to define a class that will determine how you will sort your data. This class derives from the IComparer interface and implements the Compare method. For more robust code you could check the instance type of the objects to be sure they are of the Pair type.

The third step is to sort your array of data. This can be done by using the static Sort utility method on the Array class. This method will accept any standard Array and sort it using your comparer.

using System;
using System.Collections;

namespace ConsoleApplication1
{

	/// <summary>
	/// Contains two entities. This would be more flexable
	/// if we were using templates.
	/// </summary>
	class Pair
	{	
		public String MyString
		{
			get
			{
				return _string;
			}
			set
			{
				_string = value;
			}
		}

		public int MyInt
		{
			get
			{
				return _int;
			}
			set
			{
				_int = value;
			}
		}

		private int _int;
		private String _string;
	}

	/// <summary>
	/// This class will do the comparing. Change the order of
	/// left and right to obtain an descending order.
	/// </summary>
	class PairComparer : IComparer
	{
		#region IComparer Members

		public int Compare(object x, object y)
		{
			Pair left = (Pair)x;
			Pair right = (Pair)y;
			return left.MyInt.CompareTo(right.MyInt);
		}

		#endregion
	}

	/// <summary>
	/// Summary description for Class1.
	/// </summary>
	class Class1
	{
		/// <summary>
		/// The main entry point for the application.
		/// </summary>
		[STAThread]
		static void Main(string[] args)
		{
			Pair[] pairs = new Pair[3];
			pairs[0] = new Pair();
			pairs[0].MyInt = 10;
			pairs[0].MyString = "Ten";

			pairs[1] = new Pair();
			pairs[1].MyInt = 3;
			pairs[0].MyString = "Three";

			pairs[2] = new Pair();
			pairs[2].MyInt = 1;
			pairs[2].MyString = "One";

			// Sort the array the way we want to 
			// by specifying the comparer
			Array.Sort(pairs, new PairComparer());

			// Print out the results to see if the comparing
			// was successful
			foreach (Pair pair in pairs)
			{
				Console.WriteLine(
					"Pair: {0} {1}" , 
					pair.MyInt, 
					pair.MyString);
			}

		}
	}
}

-
Drew

Re: A list of pairs (string, int) + sorting

Nicholas Cardi15-Apr-05 12:15

Nicholas Cardi

15-Apr-05 12:15

//Wrap this in a command button click event

System.Collections.ArrayList arylist = new ArrayList();

for (int i = 10; i >= 0; i--)
{
pairs values;
values.stringvalue = i.ToString();
values.intvalue = i;
arylist.Add(values);
}

IComparer comp = new MyCompare();
arylist.Sort(comp);

for(int i = 0; i<=10; i++)
{
pairs values = (pairs)arylist[i];
MessageBox.Show(values.intvalue.ToString() + " " + values.stringvalue);
}

//end wrap

private class MyCompare: System.Collections.IComparer
{
public int Compare(object x, object y)
{
pairs valuex = (pairs)x;
pairs valuey = (pairs)y;

if (valuex.intvalue < valuey.intvalue)
return -1;
if (valuex.intvalue > valuey.intvalue)
return 1;

return 0;
}
}

private struct pairs
{
public string stringvalue;
public int intvalue;
}

Forever Developing

Re: A list of pairs (string, int) + sorting

leppie15-Apr-05 21:24

leppie

15-Apr-05 21:24

If you know the upperbound of the int and its not too high and the values are not too sparse, just create a string array. :p

^{xacc-ide 0.0.15 now with C#, MSIL, C, XML, ASP.NET, Nemerle, MyXaml and HLSL coloring - Screenshots}

Embedded User Control

Larsenal15-Apr-05 8:24

Larsenal

15-Apr-05 8:24

Has anyone used embedded user controls (http://www.devhood.com/tutorials/tutorial_details.aspx?tutorial_id=187&printer=t) in a real application. I didn't even know this was possible until today.

I am building an app where the client wants drag-and-drop upload of multiple files. There is a Java tool out there, but I was considering creating an embeded user control.

Any suggestions? (No need to mention basic platform compatability issues).

Re: Embedded User Control

Nicholas Cardi15-Apr-05 12:17

Nicholas Cardi

15-Apr-05 12:17

I would see no real issues except that you will need to install .NET Framwork on the all of the machines that need this functionality.

Best of Luck

Forever Developing

Window Service Startup Mode

Hercules0115-Apr-05 7:46

Hercules01

15-Apr-05 7:46

hi all,

i created a windows service and build a controller to that service, just as the SQL Server Service Manager if any saw it. Anyway the problem is i want to control the startup mode of the windows service (Automatic, Manual, Disabled), in .Net you can specify this in the Service Installer but after that i didn't find a way to change it.

Does anyone know a way to change the startup mode of the Windows Service in .Net? i think that i foud a way to do it in win32, but i need it in .Net...

thanks for help

Re: Window Service Startup Mode

DafeNilesh27-Jan-09 8:10

DafeNilesh

27-Jan-09 8:10

The Service startup mode can be changed in C# using System.Management namespace. a sample method is given below.

/// <summary>
       /// This routine updates the start mode of the provided service.
       /// Add Reference to System.Management .net Assembly
       /// </summary>
       /// <param name="serviceName">Name of the service to be updated</param>
       /// <param name="startMode">Manual or Automatic. This parameter could probably use
       /// an enum.</param>
       /// <param name="errorMsg">If applicable, error message assoicated with exception</param>
       /// <returns>Success or failure.  False is returned if service is not found.</returns>
       public bool ServiceStartModeUpdate(string serviceName, string startMode, out string errorMsg)
       {
           uint success = 1;
           errorMsg = string.Empty;

           string filter =
               String.Format("SELECT * FROM Win32_Service WHERE Name = '{0}'", serviceName);

           System.Management.ManagementObjectSearcher query = new ManagementObjectSearcher(filter);

           // No match = failed condition
           if (query == null) return false;

           try
           {
               ManagementObjectCollection services = query.Get();

               foreach (ManagementObject service in services)
               {
                   ManagementBaseObject inParams =
                       service.GetMethodParameters("ChangeStartMode");
                   inParams["startmode"] = startMode;

                   ManagementBaseObject outParams =
                       service.InvokeMethod("ChangeStartMode", inParams, null);
                   success = Convert.ToUInt16(outParams.Properties["ReturnValue"].Value);
                   //custom method
                   errorMsg = GetErrorMsg(success) + "\n Try \"Run as Administrator\" ";
               }
           }
           catch (Exception ex)
           {
               errorMsg = ex.Message;
               throw;
           }

           return (success == 0);
       }

need help opeing projects

microuser_200015-Apr-05 6:56

microuser_2000

15-Apr-05 6:56

hellow to all
i had download some projects from this site but when i try to run them a get error and it is
the applecation for project (C:\.....THE PATH)
make sure the applecation for project type (.csproj) is installed

thank u for the help \!

Re: need help opeing projects

Judah Gabriel Himango15-Apr-05 7:00

Judah Gabriel Himango

15-Apr-05 7:00

Do you have Visual Studio installed? .csproj files are meant to be opened with the Visual Studio IDE program.

Tech, life, family, faith: Give me a visit.
I'm currently blogging about: He has a funny face. And he's my son.
Judah Himango

Can't delete BMP file in C# Win App

Khang Nguyen15-Apr-05 6:38

Khang Nguyen

15-Apr-05 6:38

Hello Gurus,
Happy Friday to Gurus. I appreciate for your looking into this and any tips or tricks.
Thanks & Happy Coding Smile | :)

Roughly what I am trying to do is:
1. Get a video frame from a webcam ExternalSource.
2. Some modifications to the bitmap of the current frame.
2. Save this frame to a Image.bmp file.
3. Display the image from Image.bmp on an ImageBox
4. Repeat from Step 1, to achieve a video-like show.

The Problem: can't delete or overide Image.bmp file with new images.

string sFileName = "C:\Temp\Image.bmp";
Image img;

// ExternalSOurce = an image frame extracted from a video stream from a webcam
ExternalSource.SaveFile(sFileName);
img = Image.FromFile(sFileName);
picControl.Image = img;
img.Dispose(); // won't help
img = null; // won't help

While (!DONE)
{

// Can't delete because file is locked until img is destroyed!
File.Delete(sFileName);
ExternalSource.SaveFile(sFileName);
img = Image.FromFile(sFileName);
picControl.Image = img;
img.Dispose(); // won't help
img = null; // won't help
}

Re: Can't delete BMP file in C# Win App

Dave Kreskowiak15-Apr-05 7:42

Dave Kreskowiak

15-Apr-05 7:42

I think you're looking for this[^] little workaround for that problem.

RageInTheMachine9532
"...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome

Re: Can't delete BMP file in C# Win App

Khang Nguyen15-Apr-05 7:50

Khang Nguyen

15-Apr-05 7:50

Dave, thanks so much for the great tip, Guru! You're always great and know so much.
Have a great weekend
Khang Smile | :)

Re: Can't delete BMP file in C# Win App

eggie515-Apr-05 20:20

eggie5

15-Apr-05 20:20

You should pass a FileStream using FileMode.Open and FileAccess.Read to the File.Delete method. Something along the lines of using a FileStream should do the trick. Hope this works for you...

/\ |_ E X E GG

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