Re: Adding Column to a ListView - C# Discussion Boards

21-Jan-04 5:37

I have a Windows Form with an empty ListView control set to Details view.
I create this dialog and attempt to add the columns from the DataSet to the ListView, but I'm having a problem.

//lets fill the results box
for(int x=0;x

Heath Stewart21-Jan-04 5:52

21-Jan-04 5:52

Either use a positive width, or -1 to set the column width to the size necessary for the header text. -2 will set the width of only the last column to the remaining size. Doing this sequentially (since each row is the last column with each iteration) might lead to such odd behavior.

Guinness4Strength21-Jan-04 5:57

21-Jan-04 5:57

MSDN says -2 will set the width to the header text, its even used in the example...

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlrfsystemwindowsformslistviewcolumnheadercollectionclassaddtopic2.asp

Heath Stewart21-Jan-04 7:50

21-Jan-04 7:50

What I read - also in MSDN but regarding the List-View common control which ListView encapsulates - described what I said before. A slight discrepency somewhere, but it really matters not.

The following code worked fine for me (both the commented source, and the uncommented):

using System;
using System.Drawing;
using System.Windows.Forms;

public class Test : Form
{
  public static void Main()
  {
    Application.Run(new Test());
  }

  public Test()
  {
    ListView lv = new ListView();
    Controls.Add(lv);
    lv.Dock = DockStyle.Fill;
    lv.View = View.Details;

    foreach (string s in new string[] {"Code", "Project", "Is", "Awesome"})
    {
//    ColumnHeader header = new ColumnHeader();
//    header.Text = s;
//    header.Width = -2;
//    lv.Columns.Add(header);
      lv.Columns.Add(s, -2, HorizontalAlignment.Left);
    }
  }
}

I didn't catch before that you were using DataColumn.ToString. There's the problem. If you look at the documentation for DataColumn.ToString (which it overrides, but be careful because classes that don't override it and inherit from Object.ToString will return their Type as string), you'll see that it returns DataColumn.Expression, which is used to filter and calculate values. Instead, use DataColumn.Caption. If the Caption is not set, the ColumnName is returned. If you prefer, you can set the Caption when creating a strongly-typed DataSet, or you can use the database column name or an ALIAS.

Guinness4Strength22-Jan-04 8:33

22-Jan-04 8:33

Very strange....I tried the following code and got the same results, a blank ListView:

for(int x=0;x<<dSet.Tables["Documents"].Columns.Count;x++)<br />
			{<br />
				ColumnHeader head = new ColumnHeader();<br />
				//head.Text=dSet.Tables["Documents"].Columns[x].ToString();<br />
				head.Text=DateTime.Now.ToString();<br />
				head.Width=-2;<br />
				head.TextAlign=HorizontalAlignment.Center;<br />
				lvResults.Columns.Add(head);<br />
			}

but if I change the -2 to 80, the ListView looks normal....I don't understand...

(I used << intentionally because the single < was interpreted as HTML and chopping off my for statement)

Heath Stewart22-Jan-04 9:26

22-Jan-04 9:26

For a <, use <

First, why not just set head.Text to dsSet.Tables["Documents"].Columns[x].Caption like I mentioned before? Read the documentation for ColumnHeader.Caption and you'll see why.

As far as this not working, you have set ListView.View to View.Details, right? ListView.HeaderStyle should also be set to something other than ColumnHeaderStyle.None.

Guinness4Strength22-Jan-04 9:33

22-Jan-04 9:33

I did try using ColumnHeader.Caption with same results, so I decided to use some other string (DateTime.Now.ToString() in this case) to see if it had anything to do with using ColumnHeader text as source. The problem is not the Text, I get the correct Text when I use ColumnHeader[x].ToString(), just the width of the columns are Zero unless i set the width to a positive value. Obviously this is not criticle, but I'd like to have the columns sized to their header, and now its kinda a mission to figure out why it doesn't work.

The following are the settings for the list view:

this.lvResults.AllowColumnReorder = true;
this.lvResults.ContextMenu = this.cmResults;
this.lvResults.Dock = System.Windows.Forms.DockStyle.Fill;
this.lvResults.FullRowSelect = true;
this.lvResults.GridLines = true;
this.lvResults.Location = new System.Drawing.Point(0, 0);
this.lvResults.MultiSelect = false;
this.lvResults.Name = "lvResults";
this.lvResults.Size = new System.Drawing.Size(536, 342);
this.lvResults.TabIndex = 0;
this.lvResults.View = System.Windows.Forms.View.Details;
this.lvResults.SelectedIndexChanged += new System.EventHandler(this.lvResults_SelectedIndexChanged);

And the HeaderStyle is set to Clickable.....

Heath Stewart22-Jan-04 9:39

22-Jan-04 9:39

Hmm, this is strange. What happens when you compile and run that code fragment I posted earlier in this thread? What version of the Framework are you using? I'm just not seeing anything wrong with your code now that you've posted about everything pertinent.

Guinness4Strength22-Jan-04 9:45

22-Jan-04 9:45

I'm using v1.1 for .NET
version 2003 of VS.NET

I get same result when I compile your code.
either I need to reinstall .NET or I'm missing something.

Heath Stewart22-Jan-04 9:49

22-Jan-04 9:49

I just compiled it for .NET 1.1 and my code works fine. WTF | :WTF:

You could try reinstalling .NET but remember that this control and many others encapsulate their Windows Common Control equivalents. Make sure you have all the latest services packs and updates first. I've followed the calls and .NET doesn't really care too much about the value of ColumnHeader.Width - it passes it to the header control for the List-View common control using SendMessage - practically unscaithed.

Guinness4Strength22-Jan-04 9:57

22-Jan-04 9:57

I've comiled your code and ran in on three machines 2 WinXP and 1 WinServer 2003, all with up2date service packs and none of them worked.....I just don't get it. Text is present, width is just zero....WTF is right.

User friendly error

Anonymous21-Jan-04 4:47

Anonymous

21-Jan-04 4:47

I'm a pretty new programmer. I'm using C#. I'm writing a program that reads and writes data to and from an MS Access database. I have the database set up so I cannot write null values to it. When I try to do so I get an error message. I understand that the database cannot accept null values but I want the user to be able to understand this as well, I want to write a custom error message. Can someone tell me how this is done or tell me where to look for more info on this topic.

thanks

Re: User friendly error

Alex Korchemniy21-Jan-04 4:54

Alex Korchemniy

21-Jan-04 4:54

Create a custom form that dispalys the message. In the catch block (if you are using try-catch) just show the form!

Re: User friendly error

Mazdak21-Jan-04 5:04

Mazdak

21-Jan-04 5:04

Or,put all the code for database in try/catch and get OleDbException,and check the Message or ErrorCode property and if it is that error,show an user friendly in MessageBox.

Mazy

No sig. available now.

Re: User friendly error

eggie521-Jan-04 12:26

eggie5

21-Jan-04 12:26

a user friendly

/\ |_ E X E GG

Custom Panel

ernst wolthaus21-Jan-04 4:24

ernst wolthaus

21-Jan-04 4:24

Please read on and help me! D'Oh! | :doh:

When you create a custom component and inherit (standard) from System.Windows.forms.Usercontrol, VS.NET shows a nice workarea in Design where you can place all kinds of winform controls like a textbox, button, etc.

But when I try to inherit from Panel, the area in Design disappears and is replaced by screen which says "to add components to your class.... click here to switch to code view" Confused | :confused:

I can't use this to make custom panels!

What I'm trying to do is the following:
I want a winform app (like Outlook) and everytime the user chooses a menuitem,I want to load the corresponding panel. I don't want to load all the panels at once, this will take to much time and memory.
So that's why I want to inherit from Panel, add the needed controls and then load the panel at runtime when needed.

Please, if you can help, mail me!
Or if you think I should tackle this another way, tell me so!

Thanks!
Ernst Wolthaus

Mazdak21-Jan-04 4:46

Mazdak

21-Jan-04 4:46

When you inherit from Panel,if you want to add controls just double click on a controls on toolbox and they added to your form,then you should manully set the positions , size and other properties in code-behind. Whats your problem with it?

Mazy

No sig. available now.

ernst wolthaus21-Jan-04 7:46

ernst wolthaus

21-Jan-04 7:46

When you inherit from Panel, you lose the design view in VS.NET. That was my problem.
And when I lose the design view, I can't just add controls visually because it just doesn't work right anymore.

But fortunately Jose gave me the solution, by added some attributes to the custom control.

Thanks anyway!

Heath Stewart21-Jan-04 5:34

21-Jan-04 5:34

If you can't use the designer, just code the controls manually.

As far as displaying custom panels (or any scrollable control, for that matter), derive your custom panel Types (classes) and store the Type of the derivative panels as properties of the item on which the action occurs, such as clicking on a menu item. Since you're dealing with MenuItems, also extend MenuItem with your own class and add a property, kind of like:

public class MyMenuItem : MenuItem
{
  private Type panelType;
  public MyMenuItem() : this(null, null) {}
  public MyMenuItem(string text) : this(text, null) {}
  public MyMenuItem(string text, Type panelType) : base(text)
  {
    this.panelType = panelType;
  }
  public Type PanelType
  {
    get { return this.panelType; }
    set { this.panelType = value; }
  }
}

Treat this menus like normal, adding them to a MenuItems collection just like normal. When a user clicks on the MenuItem, you will use that Type as you'll see shortly. For brevity, assume that each MenuItem uses the same Click event handler:

private void menu_Click(object sender, EventArgs e)
{
  MyMenuItem menu = sender as MyMenuItem;
  if (menu != null)
  {
    if (menu.PanelType != null)
    {
      // If you derived from Panel, cast to the base class here
      // (or even simply Control).
      Panel p = Activator.CreateInstance(menu.PanelType) as Panel;
      if (p != null)
      {
        p.Dock = DockStyle.Fill;
        leftContainer.Controls.RemoveAt(0);
        leftContainer.Controls.Add(p);
      }
    }
  }
}

This is just a very basic example but I hope you get the idea. Creating instances of unknown Types (or from a collection of Types, perhaps configured in a .config file) is fairly common. I do this A LOT in our enterprise app I designed. It goes much deeper than this, but this is the essential idea.