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Foreach button in my panel containing other panels

I'm using a custom Button which contains other elements and color styles like TopColor and BotColor. I need to handle this Button inside a panel with other panels.
I'm trying this:
foreach(CustomButton btn in panel1.Controls)
{
if(btn is CustomButton)
{
btn.TopColor=Color.Red;
}
Inside panel1 I'm containing other panels too. And the error I'm getting is
it can't be conversion element panel in a button.
One solution is to separate buttons in one panel. But I want to ask if there is some way to avoid other elements. The reason I don't want to use foreach (Control a in this.Controls) is it doesn't recognise my custom color style TopColor and BotColor
Take a look

Loop through all your controls (as Controls), check if it's a button, then cast it before you try and set the colour.
foreach(Control c in panel1.Controls)
{
if (c is CustomButton)
{
(c as CustomButton).TopColor = Color.Red;
}
}

I hope this solution works for you.
private void SetStylesToCustomButtons(Control.ControlCollection controls)
{
foreach (Control control in controls)
{
if (control is CustomButton)
{
(control as CustomButton).TopColor = Color.Red;
}
else if (control is Panel)
{
SetStylesToCustomButtons((control as Panel).Controls);
}
}
}

The reason you're getting an error is that you're trying to cast all your controls to CustomButton, even the panels. You already know the type that you're looking for, so you don't have to loop through every control in your panel.
Assuming all your custom buttons are in panel1 and that you don't need to recurse, you should rather filter the items down to the type that you want and then work with them:
var customButtons = panel1.Controls.OfType<CustomButton>();
foreach (CustomButton customButton in customButtons)
{
//do what you need here
}

Accessing variables dynamically in C#

I have tons of Buttons named like this x0y1
How do I access the variable name dynamically so I could loop all names by xiy1 or so.
in PHP it would be like ${"myString" . $randomvar}
I can't use a list or array because the the button already exist defined through the xaml

You can use:
var textbox =
this.Controls.OfType<TextBox>().Where(txb => txb.Name == "myString").FirstOrDefault();
This assumes you are in the context of your form (this.Controls).
And of course, don't forget to add using System.Linq;...

You can get all the textbox using this method
void AllTextBox(System.Windows.Forms.Control.ControlCollection ctrls)
{
foreach (Control ctrl in ctrls)
{
if (ctrl is TextBox)
{
if (ctrl.Name == "textBox1")
{
// do your stuf with textbox
}
}
}
}

You can create function that return control by name :
Control GetControlByName(string Name)
{
foreach(Control control in this.Controls)
if(c.Name == Name) return control ;
return null;
}
or Function with a specific control like that :
Button GetButtonByName(string Name)
{
foreach (Control c in this.Controls.OfType<Button>())
if (c.Name == Name) return c;
return null;
}

For wpf project...
Let's say you have a grid named MyGrid and there's lot of buttons on it.
You want to refer to the button named x0y1:
var btn = MyGrid.Children.OfType<Button>().Where(x=>x.Name=="x0y1");
Note: above code should work for flat structure (one level deep only).
You can achieve the same by using code provided in this thread: How can I find WPF controls by name or type?

Just call FindName("elementName"). FindName searches through all child elements of a FrameworkElement. To access any button by its name as string in a window, call the FindName() method of the window !
If your code is in a class inheriting from Window, just use:
Button button = (Button)FindName("xiy1");
If you write the code in a class not inheriting from Window but FrameworkElement, which is unlikely, use:
Window window = Window.GetWindow(this);
Button button = (Button)window.FindName("xiy1");
Check the MSDN documentation about Namescopes for more information about limitations.

Looping throughTextBoxes in a Panel

I have a panel that contains 5 textboxes, I am trying to loop through the Panel and insert the value of the textbox into the database if it is not 0.
my panel name is Panel1
I honestly do not know from where to start or how to loop in a Panel that contains textfields, any suggestions are appreciated:
Here is my try which it does not compile (I am not sure how to write a loop that loops through a panel)
const string query = "INSERT INTO deductible (number) VALUES (#yes)";
using (var command = new SqlCommand(query, conn))
{
foreach (Panel1 c in this.Controls)
{
if (c.ToString() != "0")
{
command.Parameters.AddWithValue("#yes", c.Text);
command.ExecuteNonQuery();
}
}
I also attached a screenshot of my Panel1.
Thank you.

The simple answer is
foreach(Control control in this.Controls) {
if (control is TextBox) {
// The code here ...
}
}
The problem though is that you then need to make sure that the order the textboxes are looped over is correct, which adds more maintenance work that is entirely unnecessary. A better approach would be to learn about data binding. Or even more simply, just name your textboxes and assign them directly. Either of those is preferable to using a loop I think.

One way is to iterate each control within your Panel that is a TextBox.
foreach (TextBox tb in Panel1.Controls.OfType<TextBox>())
{
if (tb.Text != "0")
{
}
}

You're trying to loop through items of type Panel1 in this.Controls. What you want to do is loop through items of type TextBox in Panel1.Controls.
foreach(Control c in Panel1.Controls) {
var textbox = Control As TextBox;
if(textbox != null){
// do stuff...
}
}
You also want to look at the Text property of the TextBox, not call ToString on it.
if(textbox.Text != "0"){ //do stuff... }
And you add a #yes parameter to the same command multiple times within the loop, without clearing out the parameters list. I'm not certain if that will work, but if it causes a problem, you should just be able to call command.Parameters.Clear to clear the old parameter before adding the new one.

Accessing programmatically created controls

I've created a series of Panels within a placeholder, inside each panel is 5 textboxes.
On a button press, I want to get the .Text from each Textbox, and the ID of the Panel. I planned to use a JaggedArray to keep track of all Panels and their internal TextBoxes.
string[][] jaggesaddress = new string[stop][]; //stop is an int and equal to amount of panels on screen.
String[] numbers = new String[stop];
int a = 0;
//Control ctrl;
foreach (Control ctrl in BookingPlaceholder.Controls) //BookingPlaceholder is placehodler ID
{
if (ctrl is Panel)
{
numbers[a] = ctrl.ID;
a++;
//ctrl.ID = numbers[a];
foreach(TextBox tb in ctrl.ID) // error here
{
}
}
}
However the second foreach loop has an error, and I am not 100% sure how to overcome this.
"Cannot convert type 'char' to 'System.Web.UI.WebControls.TextBox'"
I know that the numbers[a] does find the first panel, however it's a string with no extension of ID.
Any suggestions are appreciated.
Josh

Your inner loop is trying to iterate through a string. What you wanted was...
foreach(TextBox tb in ctrl.Controls.OfType<TextBox>())
instead of
foreach(TextBox tb in ctrl.ID)

If for more generic controls available in PlaceHolder then
you need to find textbox controls. so it is safe to check the control type also.
foreach (Control ctr in ctrl.Controls)
{
if (ctr is TextBox)
{
//Do your things
// ((TextBox)ctr).Text
}
}

Loop through controls in TabControl

I am looking for a way to loop through controls on a particular tab of a tabcontrol. For example, I have a tabcontrol with the following tabs:
Cars,
Pets,
Admin
On each of these tabs are several controls to display/edit/save data, etc. On the "Save" button, I would like to loop through the controls for that particular tab to check whether all required fields have been filled in.
So, if I am on the Cars tab and click "Save," I want to loop ONLY through the controls on the Cars tab and NOT the Pets or Admin tabs.
How can achieve this result?

As for looping through a TabControl's controls, you need to use the Controls property.
Here's an MSDN article on the TabControl.
Example:
TabPage page = aTabControl.SelectedTab;
var controls = page.Controls;
foreach (var control in controls)
{
//do stuff
}

I feel it's important to note that, in general, you should take a more structured approach to your application. E.g., instead of having all the controls on three tab pages, include exactly one UserControl on each tabpage. A CarUserControl, PetUserControl, and AdminUserControl e.g. Then each user control knows how to create the proper respective data structure so you don't have to manually munge it all together at the same level of abstraction using inter-tab loops and whatnot.
Such a separation of concerns will make it much easier to reason about your program and is good practice for writing maintainable code for your future career.

Example where I wanted to get the DataGridView in a particular tab for an application I wrote.
TabPage pg = tabControl1.SelectedTab;
// Get all the controls here
Control.ControlCollection col = pg.Controls;
// should have only one dgv
foreach (Control myControl in col)
{
if (myControl.ToString() == "System.Windows.Forms.DataGridView")
{
DataGridView tempdgv = (DataGridView)myControl;
tempdgv.SelectAll();
}
}

The Controls property is the way to go...
foreach(Control c in currentTab.Controls)
{
if(c is TextBox)
// check for text change
if(c is CheckBox)
//check for check change
etc...
}

TabControl has a SelectedTab property, so you'd do something like this:
foreach(Control c in tabControl.SelectedTab.Controls)
{
//do checks
}

foreach (Control c in this.tabControl1.SelectedTab.Controls)
{
// Do something
}

I had the need to disable or enable controls of a tab as well. I had to go a bit more generic though. Hope it helps people and I didn't make a mistake
private void toggleControls(Control control, bool state)
{
foreach (Control c in control.Controls)
{
c.Enabled = state;
if (c is Control)
{
toggleControls(c, state);
}
}
}