Develop Reference

Can we dynamically reference element (Server Side)

Say I have the elements with the ID's of "Input1", "Input2" and "Input3".
Is there a way to loop through them rather then having to write:
Input1.Value = 1;
Input2.Value = 1;
Input3.Value = 1;
in jquery you can just refrence an element like $('#Input'+i) and loop through i, something similar would be very useful in ASP code behind.

Edit: Duh, I searched again for finding all "x" controls on page and came up with the following source code:
foreach(Control c in Page.Controls)
{
if (c is TextBox)
{
// Do whatever you want to do with your textbox.
}
}
Kind of ... based on your example naming scheme you can do something like the following:
private void Button1_Click(object sender, EventArgs MyEventArgs)
{
string controlName = TextBox
for(int i=1;i<4;i++)
{
// Find control on page.
Control myControl1 = FindControl(controlName+i);
if(myControl1!=null)
{
// Get control's parent.
Control myControl2 = myControl1.Parent;
Response.Write("Parent of the text box is : " + myControl2.ID);
}
else
{
Response.Write("Control not found");
}
}
}
This will let you loop through numerically named controls but otherwise it is somewhat clunky.

If you know the parent container you can loop though its .Controls() property. If you start at the Page level and work recursively, you can eventually reach all controls on the page.
See the answer from this question for more details.

I like to keep things strongly typed, so I store them in a list. This makes the code more resilient to refactoring and there's no need to cast. It takes a slight bit more upfront work to put all your controls into the list, but to me it's often worth it.
I'm not sure what type your controls are, so I'm going to pretend they're of type Input.
var InputControls = new List<Input>(){Input1, Input2, Input3};
foreach(var input in InputControls)
{
input.Value = 1;
}

Looping through controls on a page using a masterpage

I'm trying to perform an operation on every control on a page that is inherited from a masterpage. I don't know how to access the child pages controls. I have tried recursively getting to my controls like this:
private void checkControls(ControlCollection controlcollection)
{
foreach (Control control in controlcollection)
{
if (control.Controls.Count > 0)
{
Debug.WriteLine(control.GetType().ToString());
checkControls(control.Controls);
}
else
{
Debug.WriteLine(control.GetType().ToString());
}
}
The method is called like this:
protected void resettodefault()
{
checkControls(this.Page.Controls);
}
However, the only controls that are printed from this execution are:
ASP.site_master
System.Web.UI.LiteralControl
I would prefer to access my controls directly (without recursion). Otherwise, how can I modify my recursion to get to the desired page's controls?

I would suggest using a base page instead of a master page, this way your logic for iterating over controls (and whatever you will do with that afterwards) is not tied to which master page a page is using.
As far as getting all the controls on the page, because the controls are hierarchical, as is the HTML they represent, so iterating over them recursively makes sense. However if you are dead set on not recursively getting controls something like this should work:
IEnumerable<Control> GetAllControls()
{
var allControls = new List<Control>();
var currentControls = new Queue<Control>();
currentControls.Enqueue(this.Page);
while (currentControls.Count >0)
{
var c = currentControls.Dequeue();
if (!allControls.Contains(c))
{
allControls.Add(c);
if (c.Controls != null && c.Controls.Count > 0)
{
foreach (Control e in c.Controls)
{
currentControls.Enqueue(e);
}
}
}
}
return allControls;
}
The last thing to consider is the lifecycle of the page, and when you iterate over the controls. If you try to walk to control tree too early not all controls may exist.
EDIT: Updated code.
Update
For validation purposes I would highly recommend using the built in validation controls of asp.net. You can read more about them here. This has the added benefit of providing validation on the client, providing faster UI responses and easing the load off the servers.
For resetting all the textboxes. I would recommend creating a new class for this purpose, then calling upon that class when needed instead of messing with the master page:
public class UIControlsHelper
{
public static void ClearTextboxes(Page page)
{
GetAllControls(page)
.Where(x => typeof(TextBox).IsAssignableFrom(x.GetType())
.ToList()
.ForEach(x => (TextBox)x.Text = string.Empty);
}
IEnumerable<Control> GetAllControls(Page page)
// Same as above, but with the page parameter replaced.
}
}
And in any of your pages:
UIControlsHelper.ClearTextboxes(this);

To access the controls in your child page do the following steps:
1-declare a variable of the type you want to access. For example if you want to access a Label in your child page use:
Label lbl_child=this.ContentPlaceHolder1.findcontrol("your label id in child page") as Label;
Now you have your label and you are free to make changes on it. Every change on this control will be reflected on the child control.
ContentPlaceHolder1 is your contentplace holder id so change it with your content id.

public void ClearTextboxes(Page page) {
GetAllControls(page)
.Where(x => typeof(TextBox).IsAssignableFrom(x.GetType()))
.ToList()
.ForEach(x => ((TextBox)x).Enabled=false);
}

FrozenGridView in update panel is not accessable

I have a RealWorld.Grids.FrozenGridView and after selecting several checkboxes (in the last column) on the grid I try to access the rows in the C# file to run some tasks on the selected rows, but the grid comes up as null, and when I try to findcontrol from the page based on the name of the grid the result is null.
gridname = (RealWorld.Grids.FrozenGridView)this.FindControl("gridname") as RealWorld.Grids.FrozenGridView;
the grid is located in an updatepanel so to access the grid I include the update panel in the find control as such:
UpdatePanel up1 = new UpdatePanel();
up1.ID = "updatepanelID";
Label gn = (Label)up1.FindControl("labelname");
I also tried:
label lbl = (Label)this.Page.FindControl("updatepanelid").FindControl("labelname") as Label;
this should happen in a button_click event
Does anyone have any experience with this type of issue?
Any help is appreciated!

The FindControl doesn't always work as expected. Try this recursive function and use your line of code that you have up top.
public static Control FindControlRecursive(Control ctlRoot, string sControlId)
{
// if this control is the one we are looking for, break from the recursion
// and return the control.
if (ctlRoot.ID == sControlId)
{
return ctlRoot;
}
// loop the child controls of this parent control and call recursively.
foreach (Control ctl in ctlRoot.Controls)
{
Control ctlFound = FindControlRecursive(ctl, sControlId);
// if we found the control, return it.
if (ctlFound != null)
{
return ctlFound;
}
}// we never found the control so just return null.
return null;
}
Your call would look something like this.
var ridname = (RealWorld.Grids.FrozenGridView)FindControl(this, "gridname") as RealWorld.Grids.FrozenGridView;

ASP.NET How to access a deeply nested user control on the parent page

I have a login control and at is nested 2 deep in a header control
i.e Page --> Header Control --> Login Control. I cannot get a reference to the control on the page using FindControl. I want to be able to set the visible property of the control like
if (_loginControl != null)
_loginControl.Visible = false;
I ended up using a recursive FindControl method to find the nested control.
public static 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;
}

Are you needing to disable/hide the User Control from the ASP.NET page it resides on (or does the User Control exist on a master page, say)? If it's in the same page, then in your ASP.NET page's code-behind you'd do:
MyUserControlsID.Visible = false
Where MyUserControl is the ID of your User Control. To determine the ID of your User Control look at the markup of your .aspx page and you will see something like this:
<uc1:UserControlName ID="MyUserControlsID" runat="server" ... />
Happy Programming!

A good way would be to use:
Page.FindControl()
if that yields null, the control is not there.

Try calling this.FindControl("_loginControl") or this.Page.FindControl("_loginControl").
See MSDN for method details:
http://msdn.microsoft.com/en-us/library/system.web.ui.control.findcontrol.aspx

The login control, if it's registered in the markup, will also be an instance member of your codebehind page; you can refer to it from the codebehind class as if it were a normal member, using the same name you provided as the ID (I do recommend using codebehinds for most logic, instead of inlining code in the markup, BTW).
You can also use the FindControl() method of your page, which will search its control subtree for a control with a given ID. That takes longer, so I would recommend the first option unless the logic control is added dynamically and you don't always know it's there.

private List<Control> GetAllNestedUserControl(Control ph)
{
List<Control> Get = new List<Control>();
foreach (var control in ph.Controls)
{
if (control is UserControl)
{
UserControl uc = control as UserControl;
if (uc.HasControls())
{
Get = GetAllNestedUserControl(uc);
}
}
else
{
Control c = (Control)control;
if (!(control is LiteralControl))
{
Get.Add(c);
}
}
}
return Get;
}
just call this code from you any parent page and then get any control by the following code
List<Control> Get = GetAllNestedUserControl(ph);
Label l = (Label)Get.Find(o => o.ID == "lblusername");
l.Text = "changed from master";

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.