Develop Reference

C# - Add all Input Controls to List<Controls> in TabIndex order

I have a windows form that just exists to take input from user, for all intents and purposes it is just a label and a corresponding input box (textbox, checkbox, masket textbox etc).
I have programatically placed all the input fields in a TabIndex order that is optimal for cycling through them in a way that fits with their locations (tab down each column of inputs, then to the top of the next column).
The person that I am building this project for has stipulated that only like each textbox to come available one at a time, as the previous one has been filled out. This is a crude way of doing it with no validation, but essentially something like this...
if (String.IsNullOrEmpty(textbox1.Text))
{
textbox2.Enabled = true
}
So this is fine to do with two textboxes in this example, but the form has 28 different inputs on it, so an absurd series of if statements will only be a last resort.
My thoughts has been to put all the inputs in a List, ideally in the same order as is their TabIndexes. I tried to do this using a foreach loop...
List<Control> inputsList = new List<Control>();
public void initialiseControls()
{
//control position to insert control into list at specified index
int cntrlpos = 0;
//for every control in form
foreach (Control cntrl in this.Controls)
{
//not counting labels (not input fields)
if (!(cntrl is Label))
{
//set list position to equal control's TabIndex
cntrlpos = cntrl.TabIndex;
//insert the control into the list at the position reflecting TabIndex
inputsList.Insert(cntrlpos, cntrl); //<---- Error Occurs
//ASK TEXTBOX TO OUTPUT LIST POSITION AS TEST
//foreach (var txtbx in this.Controls.OfType<TextBox>())
//{
// txtbx.Text = Convert.ToString(cntrlpos);
//}
}
}
As soon as the function is called, an exception is thrown stating that "Index must be within the bounds of the list".
When I put a breakpoint into the code, it showed cntrlpos to equal 29, which is more than the 28 total input controls there are on the form.
I don't know where to go from here, if anyone can offer some advice on the code above to place the Controls into the list in the correct order (or point me in the direction of another method to do something like this), then I would really appreciate it.
Thanks,
Mark

To make your list, try this:
List<Control> inputList =
(from Control c in getAllControls(this)
where c.TabStop
orderby c.TabIndex
select c).ToList();
Define the method getAllControls elsewhere in your form class:
IEnumerable<Control> getAllControls(Control parent)
{
foreach (Control control in parent.Controls)
{
yield return control;
foreach (Control descendant in getAllControls(control))
yield return descendant;
}
}
(Taken and modified slightly from Recursive control search with Linq)
This will make it so that you get even nested controls (such as those in panels or groupboxes).
You can't just use the TabIndex as an index into your list, because even stuff like labels have tab indices, which will mess up your indices.

I think you've over complicated it...
Just use Control.GetNextControl:
Retrieves the next control forward or back in the tab order of child
controls.
For example, with just TextBoxes:
private void textBoxes_TextChanged(object sender, EventArgs e)
{
Control ctl = (Control)sender;
if (!String.IsNullOrEmpty(ctl.Text))
{
Control next = this.GetNextControl(ctl, true);
if (next != null)
{
next.Enabled = true;
}
}
}
Obviously you might need a slightly more complicated check for some other types of controls in a different handler, but you'd still just grab the next control to enable using GetNextControl().

Set Properties of User Control on Event Using FindControl

I have a user control that is dynamically loaded in the the page load:
protected void Page_Load(object sender, EventArgs e)
{
MyControl ctl = (MyControl)LoadControl(controlPath);
ctl.ID = "mycontrol";
this.MyControlPlaceHolder.Controls.Add(ctl);
}
Front End of the Page:
<asp:PlaceHolder runat="server" ID="MyControlPlaceHolder"></asp:PlaceHolder>
I have an click event on the page that initiates and postback and calls a method where I'm trying to find the control and set some properties:
MyControl ctl = (MyControl)FindControl("mycontrol");
if (ctl != null){
ctl.MyProperty = true;
Response.Write("success");
}
else
Response.Write("fail");
This is writing fail after the postback, so it seems like I'm doing something incorrectly in finding the control. What is the best way to do this?
EDIT:
I switched it to MyControl ctl = (MyControl)this.MyControlPlaceHolder.FindControl("mycontrol");
This made it so it was finding the control, however, when the control loads after the postback, it appears as though the property is not set.

You have to use a recursive FindControl implementation because FindControl will only find direct childs. Your control is inserted in a naming container at a lower level. A generic FindControlRecurisve from MSDN:
private Control FindControlRecursive(Control rootControl, string controlID)
{
if (rootControl.ID == controlID) return rootControl;
foreach (Control controlToSearch in rootControl.Controls)
{
Control controlToReturn =
FindControlRecursive(controlToSearch, controlID);
if (controlToReturn != null) return controlToReturn;
}
return null;
}
from MSDN
Or, if you only have one specific conatiner like in your sample:
MyControl ctl = this.MyControlPlaceHolder.FindControl("mycontrol");
if (ctl != null){
ctl.MyProperty = true;
Response.Write("success");
}
else
Response.Write("fail");
ViewState enable your control
public class MyControl:Control
{
public bool MyProperty
{
get
{
return ViewState["my"] != null? (bool) ViewState["my"]: false;
}
set
{
ViewState["my"] = value;
}
}
}

Try moving the code to dynamically add the control into Init instead of load. I can't be sure but there are a lot of things that happen between Init and Load and if your control is not present and accounted for it may cause issues like this.

You added the Control in the controls collection of a placeholder.
Apart of what control is your dynamically created control, if you want to looking for your dynamically added control in that way you have to do a recursive search starting from the root (maybe the page), so, if you surf over the net, you could find good solutions for that.
Personally I prefer solutions with: generics support and expressed as extension methods, so you could use the solution everywhere. These are some usefull links
Recursive Find Control with generics
Recursive Find Control with generics by extension method
Recursive Find Control with generics by extension method and linq support/example
hope this helps

How to find a panel and add control to it from it's code behind

In a master page I got a panel which I want to add controls to it from the master page's code behind as follow:
var cphRegionName = this.Page.FindControl("pnlLeft") as Panel;
cphRegionName.Controls.Add(uc);
but I get this error:
Object reference not set to an instance of an object at cphRegionName.Controls.Add(uc);
I have tried all possible other ways, but get the same error.
The reason I user FindControl to access the PANEL is the panel's name is dynamic ("pnlLeft"), reading from Database.

The FindControl method doesn't work recursively. This means that unless your control was added directly to the page, it would not find it.
If you know the container control, use FindControl on that and not on the Page.
If you don't, you could use a a function like this to solve the problem
private Control FindControlRecursive(Control root, string id)
{
if (root.ID == id)
{
return root;
}
foreach (Control c in root.Controls)
{
Control t = FindControlRecursive(c, id);
if (t != null)
{
return t;
}
}
return null;
}

FindControl is not recursive, so you have to make sure you're calling it on the correct container. It doesn't look like the panel is defined at the root based on the null reference.
Try calling FindControl on the parent of the panel

How to find all controls in Gridview?

I have a gridview which contains controls like checkbox dropdownlist textbox etc.. These controls are in TemplateField and some are in updatepanel in gridview. There is a EditTemplateField which has some controls and a button. When grid is in edit mode, Now I have to find all controls in this EditTemplateField in button click event. I know that this can be done using foreach loop but don't know how?

You can use the grid EditIndex to find the row that contains the controls that are in edit mode. From there you can get the control using the control ID.
TextBox txtItem = (TextBox)Grid1.Rows[Grid1.EditIndex].FindControl("txtItem");
To find all controls then try this:
foreach(Control c in Grid1.Rows[Grid1.EditIndex].Controls)
{
// do stuff in here.
}
If you have container controls in the row, and need to find things inside of them, then you need do do something to recurse down into their controls.
I don't understand though why you would need to loop though the controls, usually the controls in the edit template will be fixed, and you know what they are so accessing them directly with Findcontrol is the way to go.

If you mean in code you can do it like this:
foreach ( GridViewRow row in MyGridView.Rows )
{
TextBox myTextBox = (TextBox)row.FindControl("myTextBox");
}

Here's a nifty utility method. It's recursive so it will find nested stuff e.g.
var listOfControls = Utility.FindControlsOfType<TextBox>(yourGridRow);
If you don't know the exact type of the nested controls, use FindControlsOfType<WebControl> instead.
public static class Utility
{
public static List<T> FindControlsOfType<T>(Control ctlRoot)
{
List<T> controlsFound = new List<T>();
if (typeof(T).IsInstanceOfType(ctlRoot))
controlsFound.Add((T)(object)ctlRoot);
foreach (Control ctlTemp in ctlRoot.Controls)
{
controlsFound.AddRange(FindControlsOfType<T>(ctlTemp));
}
return controlsFound;
}
}

Take the generated html using Firebug and using http://jsfiddle.net you can include jquery and play with the html.
Add the event handler to the edit button like
For example
function edit(this)
{
var textboxID = $(this).parent().find("[id$='textBoxId']");
}

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.