We Keep Coding

How to show an ErrorProvider error icon next to a TabPage header?

Edit:
This is not a duplicate of Icons in TabControl C# - How?. The question there is about adding icons to tab pages. Here it is about how the change the error provider error icon position to be inside the header instead of to the right of the tab page itself. Also, the error provider error icon has the functionality that when you hover the mouse on it, you see the error text, which you do not see if you simply add an icon to the header.
I have a form with a TabControl. The form has also an ErrorProvider. When I try to use the following code:
errorProvider1.SetError(tabPage1, "error");
The error icon is shown to the right of the tab page, and it is cut-off by the tab control itself:
I would like the icon to be shown next to the tab page header. Something like this (made with Photoshop):
I do not know where to start, or how to approach this.
Edit:
I have a class responsible for adding errors to a control, and showing them using an error provider. This class is used for TextBoxes, NumericUpDowns etc. I would like to use it also for TabPages. The problem is that when I use it for tab pages I get the result shown above. The trick of adding an error icon to the header using an ImageList and then add a tooltip is not good, because it is specific to tab pages, and I cannot implement it in my class which is general to all controls. So I really need to change the settings of the tab page so when I use errorProvider.SetError(...) it is shown in the header.

ErrorProvider shows error icon of the TabPage in tab page's client area.
By playing with IconAlignment or IconPadding, you can show error icon of TabControl on one of the tab pages' headers, but it's error icon for the whole TabControl.
In a real application each of the tab pages can contain controls which are not valid and you may want to show the validation icon on tab pages not for the tab control.
My suggestion is using tab page icon by setting ImageList containing the error icon as image list of the TabControl and by setting ImageIndex of the TabPage, show or hide the image icon. This way you can show the error icon for every tab page which needs it:
Example
To setup the example, follow these steps:
Create a Form.
Drop a TabControl, an ErrorProvider and an ImageList on the Form.
Set ImageList property of tabControl1 to imageList1.
Drop two TextBox on tabPage1.
I assume, just for example, you are going to validate these two text box controls using Validating event. The key point is here. When you validate any control, check if it's hosted in a TabPage, check validity of all children of TabPage and set the error icon based on that:
protected override void OnLoad(EventArgs e)
{
base.OnLoad(e);
this.AutoValidate = AutoValidate.EnableAllowFocusChange;
imageList1.ColorDepth = ColorDepth.Depth32Bit;
imageList1.Images.Add(errorProvider1.Icon);
tabControl1.ImageList = imageList1;
textBox1.Validating += textBox_Validating;
textBox2.Validating += textBox_Validating;
}
private void textBox_Validating(object sender, CancelEventArgs e)
{
var textBox = (TextBox)sender;
if (string.IsNullOrEmpty(textBox.Text))
{
this.errorProvider1.SetError(textBox, "Value is required.");
e.Cancel = true;
}
else
this.errorProvider1.SetError(textBox, null);
var tabPage = textBox.Parent as TabPage;
if (tabPage != null)
ValidateTabPage(tabPage);
}
void ValidateTabPage(TabPage tabPage)
{
var tabIsValid = tabPage.Controls.Cast<Control>()
.All(x => string.IsNullOrEmpty(errorProvider1.GetError(x)));
if (tabIsValid)
tabPage.ImageIndex = -1;
else
tabPage.ImageIndex = 0;
}

You can do the following.
Rectangle rc = tabControl1.GetTabRect(0); // Replace with the index of Tab required
errorProvider1.SetIconPadding(tabControl1, -rc.Left-20);;
errorProvider1.SetError(tabControl1, "Error String");
You also need to set
errorProvider1.SetIconAlignment(tabControl1, ErrorIconAlignment.TopLeft);
Sample (With Second Tab Selected - based on comments),
You would need to prepend whitespace to your TabPage Text to ensure there is sufficient space for showing the icon
With Icon on Second Tab

Is it possible to add more than one panel in same location

i'm using telerik control.
So i want to ask,
In winforms application ,Is it possible to add more than one panel in same location and display one at a time just like show/hide property.

Make sure you have placed all panel control in same container or form. then you can use Visible property to show and hide panel. BringFront and SendToBack function will be used to bring panel on top or send it to back. If you have placed any panel in another panel then that will be disappeared when you Hide parent panel. So, Make sure all panels' parent control must be same. To determine the parent control simply select that panel and press escape key to select their parent.
private void LoadPanels()
{
panel1.Location = new Point(10,10);
panel2.Location = new Point(10,10);
panel3.Location = new Point(10,10);
panel4.Location = new Point(10,10);
panel5.Location = new Point(10,10);
VisiblePanel("panel1");
}
private void VisiblePanel(string panelName)
{
string[] panels = new string[]{"panel1","panel2","panel3","panel4","panel5"};
for (int i=0;i<panels.Length;i++)
this.Controls[panels[i]].Visible = (panels[i] == panelName);
this.Controls[panelName].BringToFront(); //Not required you can remove this line.
}

Here's a slightly different approach you might want to consider...
Are you wanting to be able to programmatically select the contents of a rectangular area at runtime, selecting among various controls to display? If so, you could use a custom TabControl which has its tabs (not the pages) hidden.
Then you can select which page is displayed by programmatically changing its SelectedIndex property at runtime.
Doing it like this means that your form editor will show a normal tab control, which allows you to much more easily add the content to each page - but at runtime the tabs will be hidden from the user; they will just see the contents of the currently selected page.
See Hans Passant's answer here for how to create such a custom tab control.
(However, you might also want to override the OnKeyDown for the custom tab control in order to ignore Ctrl-Tab.)

Select Tab on form initialization

This is stupid and I did it before, but now its not working and I cant find a solution online. I have a form and one tab page. on the tab page there are 4 tabs. how can I make the 4th tab selected when the form loads? I also want to use the tab's text, or name, and not the tab index.

Just select the tab in your form constructor. The boilerplate code is:
public Form1() {
InitializeComponent();
tabControl1.SelectedTab = tabPage4;
// or:
tabControl1.SelectedIndex = 3;
}

You need to loop through the tabs to find the one you want, then set the TabControl's SelectedTab property.

Copy TabControl Tab

I searched the internet for this but i couldn't find how to do it with C#
What i am trying to do is make it so that when i click on my NewTab button, a new tab appears with the same controls that were on the first tab. I saw some information on how to add a UserControl to your form, but C# doesn't have anything like that.
And for everyone who would say "Post your code", i don't have any, so don't bother saying that, the only code i have is the code for the program and that wouldn't help anyone.

EDIT
I have rewritten my solution to use reflection.
using System.Reflection;
// your TabControl will be defined in your designer
TabControl tc;
// as will your original TabPage
TabPage tpOld = tc.SelectedTab;
TabPage tpNew = new TabPage();
foreach(Control c in tpOld.Controls)
{
Control cNew = (Control) Activator.CreateInstance(c.GetType());
PropertyDescriptorCollection pdc = TypeDescriptor.GetProperties(c);
foreach (PropertyDescriptor entry in pdc)
{
object val = entry.GetValue(c);
entry.SetValue(cNew, val);
}
// add control to new TabPage
tpNew.Controls.Add(cNew);
}
tc.TabPages.Add(tpNew);
Some information can be found here.
http://www.codeproject.com/Articles/12976/How-to-Clone-Serialize-Copy-Paste-a-Windows-Forms

Your best bet would be to look at this article:
Code Project
Then apply the following code to add the cloned control (this would be in your button click handler code (based on article):
private void button1_Click(object sender, EventArgs e)
{
// create new tab
TabPage tp = new TabPage();
// iterate through each control and clone it
foreach (Control c in this.tabControl1.TabPages[0].Controls)
{
// clone control (this references the code project download ControlFactory.cs)
Control ctrl = CtrlCloneTst.ControlFactory.CloneCtrl(c);
// now add it to the new tab
tp.Controls.Add(ctrl);
// set bounds to size and position
ctrl.SetBounds(c.Bounds.X, c.Bounds.Y, c.Bounds.Width, c.Bounds.Height);
}
// now add tab page
this.tabControl1.TabPages.Add(tp);
}
Then you would need to hook the event handlers up. Will have to think about this.

I know it's an old thread but I just figured out a way for myself and thought I should share it. It's really simple and tested in .Net 4.6.
Please note that this solution does not actually create new controls, just re-assigns them all to new TabPage, so you have to use AddRange each time you change tabs. New tab will show the exact same controls, content and values included.
// Create an array and copy controls from first tab to it.
Array tabLayout = new Control [numberOfControls];
YourTabControl.TabPages[0].Controls.CopyTo(tabLayout, 0);
// AddRange each time you change a tab.
YourTabControl.TabPages[newTabIndex].Controls.AddRange((Control[])tabLayout);

How to close tab page on tabcontrol by tab page's name

In c# how can I destroy a tab on a tab control by targeting it's name? I've a tab named "Hello!" and I'd like to close it programatically. There's no guarantee that it will be the selected tab at the time.

The TabControl class provides a TabPages property that returns a TabPageCollection containing all of the TabPages in the control.
So you can use the Item property to retrieve the TabPage with the specified name.
For example, if the tab page you want is named "Hello!", you would write:
var tabPage = myTabControl.TabPages["Hello!"];
To remove the TabPage from the control, use the RemoveByKey method:
myTabControl.TabPages.RemoveByKey("Hello!");
Of course, in order for this to work, you'll need to make sure that you've set the keys of your TabPages to match the caption text they display.

You can try something like this:
for (int i = tabControl1.TabPages.Count - 1; i >= 0; i--) {
if (tabControl1.TabPages[i].Text == "Hello!")
tabControl1.TabPages[i].Dispose();
}
I'm assuming you meant the "Text" of the TabPage, since "Hello!" wouldn't be a valid name for a control.
Note: this code will dispose of any TabPage that says "Hello!"