Develop Reference

How to access the Items of a User Control

I have a C# Form that prints multiple instances of a User Control. Let's say that the form prints 5 instances of the User Control (Please see the link attached). How can I store/save the data inputted in all User Controls? Thanks
Here is the screenshot of the C# Form:

You'll have to store the User Controls when you instantiate them in a List or something.
You could have a class like this:
class SomeUC : UserControl
{
public SomeUC()
{
}
// A public method.
public string GetData()
{
return textBox1.Text;
}
}
Where textBox1 is the Name of a TextBox in your SomeUC
And then inside your main or something.
// Instantiate a List that will hold your UserControls, this has to be outside all methods
List<SomeUC> list = new List<SomeUC>();
// And now when you want to build your UCs
// Instantiate your UserControl
SomeUC uc1 = new SomeUC();
// Store your UserControl in a List or something (Can't help you with that)
list.Add(uc1);
Add as much as you want.
A List is not the only way you can do that, but since you don't know how many UserControls you're going to build beforehand, it makes since to use a List.
And then you can access them from the list by their index.
SomeUC uc1 = list[0];
string data = uc1.GetData();
This is an example of accessing one control (the TextBox) in your SomeUC. For other classes (such as the ComboBox) the interaction is different. Meaning you won't have a Text property in the ComboBox. You'll have to figure out things like that on youself. A little research is what it takes. You can always come back if you couldn't find a solution for something.

You can create a property like this for each item in user control.
public string DG
{
get
{
return txtDG.Text;
}
set
{
txtDG.Text = value;
}
}
Then you can access the control value by using following line in your form.
supposed you have created a usercontrol MyControl and you have placed some object of this control in FlowLayoutPenal (pnlFLP).
To get value from control
string DG = ((MyControl)pnlFLP.Controls[0]).DG;
To set value in control
((MyControl)pnlFLP.Controls[0]).DG = "1";

Try this code for accessing user control in the page
Dim txtName As TextBox = TryCast(UserControlName.FindControl("txtName"), TextBox)

Accessing and Setting Winforms Control at runtime

I've built a Winforms table layout which has many elements in each cell. What I'm trying to do is enumerate all controls of a particular type which I'm concerned with, and remove their corresponding Click values. This something done at runtime, which is why I'm not just setting the controls initial properties.
I've tried working with the Control.ControlCollection property although I've not had much luck, as it's not IEnumerable. Alternative I have the following code but the problem is the control is never found in Controls and a Null Reference exception is thrown because I'm, trying to set .Click on an empty object, but surely this object should exist! Help!?
for (int row = 1; row < tblLayoutPanel.RowCount; row++)
{
for (int column = 0; column < tblLayoutPanel.ColumnCount; column++)
{
Type controlType = tblLayoutPanel.GetControlFromPosition(column, row).GetType();
if (controlType == typeof(CTLLabel) ||
controlType == typeof(OutputLabel))
{
Controls[tblLayoutPanel.GetControlFromPosition(column, row).Name].Click += null;
// Control is never found! *why?*
}
}
}

The reason is that the parent control of the control that you are getting using GetControlFromPosition method is tblLayoutPanel. You are trying to get the child control of the tblLayoutPanel in the parent of the tblLayoutPanel control instead of tblLayoutPanel.Controls collection.
Instead of accessing the control like this, why you don't just use the control you've got by using GetControlFromPosition method. Try this:
tblLayoutPanel.GetControlFromPosition(column, row).Click

How to access TabPages that are created in real-time?

Some inits done earlier in the code...
private List<System.Windows.Forms.TabPage> tab_pages = new List<System.Windows.Forms.TabPage>();
int tab_increment = 0;
Somewhere in the code, I create a bunch of tab pages in real-time.
for (i=0; i<5; i++)
{
tab_pages.Add( new System.Windows.Forms.TabPage() );
tab_pages[tab_increment].Location = new System.Drawing.Point(4, 22);
tab_pages[tab_increment].Name = 1 + tab_increment.ToString();
tab_pages[tab_increment].Size = new System.Drawing.Size(501, 281);
tab_pages[tab_increment].Text = tab_increment.ToString();
this.tabControl.Controls.Add(tab_pages[tab_increment]);
tab_increment += 1;
}
Now I would like to access elements that are these tab pages. Also let's pretend that I created different elements on each page (example, tabPage[0] a button, tabPage[1] a checkbox, etc), how do I access them knowing that everything was added dynamically?

Check this approach:
void Walk(Control control)
{
foreach (Control c in control.Controls)
{
//just walking through controls...
//...do something
//but remember, it could contain containers itself (say, groupbox or panel, etc.)...so, do a recursion
if (c.Controls.Count > 0)
Walk(c);
}
//or
foreach (Button btn in control.Controls.OfType<Button>())
{
//an example of how to walk through controls sub array of certain type
//this loop won't have a single iteration if this page contains no Buttons
//..so you can replace Button
//and have some certain code for different types of controls
}
}
And launch it for tabcontrol:
foreach (TabPage page in tabControl1.TabPages)
Walk(page);
I guess there is no special need to have separate collection of tabpages for one tabcontrol, as soon as it has TabPages property.
In the code above I used Enumerable.OfType Method to get a subcollection of controls of certain type.
As for your code, try this:
for (int i = 0; i < 5; i++)
{
this.tabControl.Controls.Add(new System.Windows.Forms.TabPage());
this.tabControl.TabPages[i].Text = i.ToString();
//...do whatever you need
//...
//besdies, I think, ther's no need in tab_increment...loop index works well enough
}

In order to add pages, I think that using
tabControl.TabPages.Add(new TabPage("Name"));
or in your case
this.tabControl.TabPages.Add(tab_pages[tab_increment]);
is more suitable.
In order to access them you could use
TabPage tp = tabControl.TabPages[i]; //where i is the index of your TabPage
and you can use TabPage.Controls.Add of the Controls property to add any Control on the TabPage like:
Button btn = new Button();
btn.Name = "Button name";
tp.Controls.Add(btn);

You can use the Controls property on the TabPage object. Each control in the collection is given to you as a Control, and it is up to you to cast them to the type that you want.

Get values from dynamic controls with c#?

I created a few radiobuttonlist controls on my project, they're created every time the page is loaded, i want to get the value of the radiobutton that the user has selected, but since my radiobuttons were created dynamically, i don't know how to acces to their values nor how to create their event handlers. Is there a way to assign a name or id to the control when i create it?
i hope you can help me.
I create a seires of radiobuttlist on the page_load event, with the text and their values been pulled out of a database. now, the user has to choose one of the options from that radiobuttlist and i want to get the value of the radiobutton the user checked. how do i do that if i don't know the name nor the id of the radiobuttlist since they're created dynamically.
this is what i've got:
for (int i = 3; i < numfields; i++) {
if (dr[i].ToString() != "" && dr[i] != null){
r.Items.Add(new ListItem(dr[i].ToString(), dr[i].ToString()));
//r.SelectedIndexChanged += new EventHandler(rowSelectedIndex);
}
}
so basically i use my datareader to loop through the data in the database, if the value from the field isn't empty or null, then i add an item to the radiobuttlist called "r"
i tried to create an eventhandler for that too, but since i have never worked with them i really don't know what to do. :(
I'm so sorry if i seem way too pathetic.

Taking a quick look at your code:
for (int i = 3; i < numfields; i++) {
if (dr[i].ToString() != "" && dr[i] != null){
r.Items.Add(new ListItem(dr[i].ToString(), dr[i].ToString()));
//r.SelectedIndexChanged += new EventHandler(rowSelectedIndex);
}
}
The most obvious thing that jumps out is your if statement. You should first check for null:
if (dr[i] != null && dr[i].ToString() != ""){
As if dr[i] is null, you'll get an exception (as you'll be trying to call the ToString() method on a null object.
If the contents of dr are always going to be strings, you might consider writing:
if(!String.IsNullOrEmpty(dr[i]){
I also note you start your indexing at 3 - is this because you want to skip the first 3 fields?
Wherever you create your variable, 'r', you can set the name and ID properties. You can use the ID property to look for the control on PostBack. So if you created your radiolist like so:
RadioButtonList r = new RadioButtonList();
r.Id = "MyRadioButtonList";
r.SelectedIndexChanged += MyRadioButton_SelectedIndexChanged;
Which would point at the following event handler:
private void MyRadioButton_SelectedIndexChanged(Object sender, EventArgs e) {
... Do Stuff ...
}
There are several ways of finding your control when you post back; you can look in the Request.Forms collection for a control matching the name of the control you submitted, or, more appropriately, you can use the FindControl method with the ID you gave the control. See C#, FindControl for a post with a method (by Jeff Atwood!) that will search the entire hierarchy of controls for your control.
When you add a dynamic control is important, too. If you add it too late in the page lifecycle then it will not be available on PostBack. See http://support.microsoft.com/kb/317515 for more details on just when to add a control. There are plenty of resources for Dynamic ASP.Net controls around too.

You could put your RadioButton into a list as you create them. This is also when you want to add your handlers.
RadioButton rb;
for (int i = 1; i < 5; i++)
{
rb = new RadioButton();
rb.AutoSize = true;
rb.Location = new System.Drawing.Point(25, (i*25) + 25);
rb.Name = "radioButton" + i.ToString();
rb.Text = "radioButton" + i.ToString();
//Add some event handler?
this.Controls.Add(rb);
lstRadioButton.Add(rb);
}
Whenever you want to know which one is selected you can do a foreach loop of your list and look if your RadioButton is checked.
foreach (RadioButton rButton in lstRadioButton)
{
if (rButton.Checked == true)
{
//Do something
}
}

You are maybe searching for TagName property if the programmatic name isn't enough for you.

The problem is that you are creating the controls in page_load. In order for their values to be posted back into the controls correctly, you must move this creation into the page_init method and recreate them every time.
Then, in page_load, you can access the values in the controls correctly. If you give them IDs using a consistent naming convention, you will be able to find them using the FindControl method or, in page_init, you can store them in a collection at the page or user control level.

How to Dynamically get All controls (and it's IDs) in an aspx Page?

HEllo, I need to dynamically activate fields in a page according to the service that is going to be executed...
Let me explain:
There's a page with all the possible fields and a ListBox with all the selected services to be executed, then when the user selects which service to execute (change a car plate, for example), then I need to activate only the field(s) that the service require... (The realationship between Services and Fields are stored in a database).
public void CheckAll(int pService_Id, Control pPage)
{
foreach (Control control in pPage.Controls)
{
busExecutaServico vExecuta = new busExecutaServico();
if (vExecuta.EnableField(control.ID.ToString(), Convert.ToInt32(listBoxServices.SelectedValue)))
{
switch (control.GetType().ToString())
{
case "TextBox":
TextBox controleText = (TextBox)Page.FindControl(control.ID.ToString());
controleText.Enabled = true;
break;
Note that busExecutaServico is the class which contains the method (EnableField) for checking if the selected item matches any field on the database..
I can't seem to get the control.ID.ToString() to work properly (the ID always comes as NULL)
If anyone can help me solve this, or if there's another way (even if it's completely different from what i'm trying), it would be of great help. thanks

I like to use a recursive function for locating controls by either type or ID.
public Control FindControlRecursive(Control rootControl, string controlId)
{
if (rootControl.ID == controlId)
return rootControl;
foreach (Control control in rootControl.Controls)
{
Control foundControl = FindControlRecursive(control, controlId);
if (foundControl != null)
{
return foundControl;
}
}
return null;
}
public Control FindControlRecursive(Control rootControl, Type type)
{
if (rootControl.GetType().Equals(type))
return rootControl;
foreach (Control control in rootControl.Controls)
{
Control foundControl = FindControlRecursive(control, type);
if (foundControl != null)
{
return foundControl;
}
}
return null;
}
You can adapt these to first return a collection of controls, then process them later. Might be easier to keep track of what's happening.
I learned this technique here: http://www.west-wind.com/Weblog/posts/5127.aspx

Be aware that FindControl only searches the current naming container so Page.FindControl will only find controls that are added directly to Page. For example, if you had a repeater control that had the controls you were looking for and it was added to Page, you could find your repeater control via Page.FindControl but it wouldn't find child controls within your repeater, you'd have to recursively perform the FindControl on all container controls in the page.
This might seem a bit strange but it allows you to have controls with the same ID existing on the same page. For example, if you had 10 instances of a user control with textboxes within them called "MyName", you'd really want them to not being over-writing each other's 'MyName' fields!

Your code will come across a null for an ID unless every control has been given an ID.
Also why use:-
TextBox controleText = (TextBox)Page.FindControl(control.ID.ToString());
at all instead of:-
TextBox controleText = (TextBox)control;
and indeed since you only want to change the Enabled property consider:-
((WebControl)control).Enabled = False;
That I suspect will eliminate many case statements.

In your code you don't need to search any control - you already have it in 'control' variable. You even don't need to cast it to TextBox, just to a WebControl, just do this:
...
if (vExecuta.EnableField(control.ID.ToString(), Convert.ToInt32(listBoxServices.SelectedValue)))
((WebControl)control).Enabled = true;
P.S. control.ID is already string, so you should remove any ID.ToString() also.