Develop Reference

How to find first editable control to focus on in a page

My current function only finds first Textbox which is not totally correct. Control class doesn't have IsEditable property.
private static Control FindFocusableControl(Control CurrentControl)
{
if (CurrentControl.Visible)
{
if (CurrentControl is TextBox)
{
return CurrentControl;
}
if (CurrentControl.HasControls())
{
foreach (Control CurrentChildControl in CurrentControl.Controls)
{
Control focusableControl = FindFocusableControl(CurrentChildControl);
if (focusableControl != null)
{
return focusableControl;
}
}
}
}
return null;
}

On the first recursion for the first child control, the child control is probably not visible so the routine exits.
if (CurrentControl.Visible)
You might need a different kind of check at this point, perhaps check for textbox first, then if visible.

How to change the readonly property false of textboxes in winform?

How can we change the ReadOnly property of all textBoxes in a winform that is true to false i'm trying using this code but this prompt me object null reference error...
private void TextBoxesReadOnlyTrue(Control.ControlCollection cc)
{
foreach (Control ctrl in cc)
{
TextBox tb = ctrl as TextBox;
if (tb.ReadOnly)
{
tb.ReadOnly = false;
}
}
}

That's because not all the controls in cc are TextBoxes. So when you try converting them to a TextBox, the variable is null. When a variable is null, you cannot access any properties on that variable, or you'll get an error. So anytime a variable can be null, you MUST first test whether it is null.
Here's the modified if command that you'll want to use to fix your problem:
if (tb != null && tb.ReadOnly) { tb.ReadOnly = false; }
So i appologize that i overlooked that your TextBoxes can be contained in other container controls. Yes, that means you need to do 1 of 2 things: 1: You can move the TextBoxes outside the GroupBox. haha. I'm just joking. Yes, that can solve that problem but then you have worse problems. The correct way is to recursively call your method for every control that has controls in its Controls property. Every control has this property but it seems it is empty (but not null) in controls that are not containers. (I just learned today that every control has this Controls property, so i've updated my code to reflect this.)
So for this real solution, i suggest something similar to this:
private void TextBoxesReadOnlyTrue(Control.ControlCollection cc)
{
foreach (Control ctrl in cc)
{
TextBox tb = ctrl as TextBox;
if (tb != null && tb.ReadOnly)
{ tb.ReadOnly = false; continue; }
if (ctrl.Controls != null && ctrl.Controls.Count > 0)
{ TextBoxesReadOnlyTrue(ctrl.Controls); }
// this recursively calls this same method for every control ...
// that is a container control that contains more controls, ...
// such as GroupBoxes, Panels, etc.
}
}

first you would like to use a function like this:
Recursive get controls
then you do the following
private IEnumerable<T> GetControls<T>(Control.ControlCollection ctrls)
{
foreach (object ctrl in ctrls)
{
foreach (var item in GetControls<T>(((Control)ctrl).Controls))
{
yield return item;
}
if (ctrl is T)
yield return (T)ctrl;
}
}
foreach(var txtbox in GetControls<TextBox>(form.Controls)
{
txtbox.ReadOnly = 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;

Set Focus to Any Control After PostBack

First I have 3 TextBoxes, a DropDownList, a CheckBox, and 2 LinkButtons in a table. The TextBoxes and DropDownList must do an AutoPostBack because there are some calculations being done on the server side which called by OnTextChanged.
My issue here is that after the content of any Control (which requires a PostBack) changes and you attempt to move focus to any other Control on the page (whether it be tabbing or using the mouse to click on any other Control) the focus does not move to the next Control or the Control you clicked.
I tried using a method which finds the current Control and based on the TabIndex, adds 1 which moves the focus to the next control. The problem here is that it does not allow for focus to be set on any other Control other than that one with the next TabIndex. To better explain here is an example of the situation.
Example: I have TextBox1, TextBox2, and TextBox3. I change the content in TextBox2 then want to move backwards to TextBox1. When I click in TextBox1 the focus is set to TextBox3 since the code is using the order of the TabIndex. ** A key factor here is that TextBox1 DOES get focus before the server side code fires but then loses focus and sets it on TextBox3 **
To me, it seems like the only way this can be accomplished would be to add a function on the client side which finds the Control with focus before the PostBack occurs, then reset the focus on that Control after the server side code completes. It does not seem like anything I do on the server side will work since the focus has already been lost when this occurs.
I have searched and searched but have not been able to find any solution to this particular issue, everything I have found deals with setting focus to the NEXT Control instead of the Control you want to have focus. Any help would be greatly appreciated. Thank you in advance.
Here is the code I am using to move to the next Control based on the TabIndex but this does not work in my situation.
protected void Page_Load(object sender, EventArgs e)
{
WebControl ctrl = GetPostBackControl() as WebControl;
if (ctrl != null && !SetNextFocus(Controls, ctrl.TabIndex + 1)) { ctrl.Focus(); }
}
public Control GetPostBackControl()
{
Control control = null;
string ctrlname = Request.Params.Get("__EVENTTARGET");
if (ctrlname != null && ctrlname != string.Empty)
{
control = FindControl(ctrlname);
control.Focus();
}
else
{
foreach (string ctl in Request.Form)
{
Control c = FindControl(ctl);
if (c is Button)
{
control = c;
break;
}
}
}
return control;
}
private bool SetNextFocus(ControlCollection controls, int tabIndex)
{
foreach (Control control in controls)
{
if (control.HasControls())
{
bool found = SetNextFocus(control.Controls, tabIndex);
if (found) { return true; }
}
WebControl webControl = control as WebControl;
if (webControl == null) { continue; }
if (webControl.TabIndex != tabIndex) { continue; }
webControl.Focus();
return true;
}
return false;
}

Try doing something like this to retain focus after postback:
/// <summary>
/// Overrides the OnLoad event moves the cursor to the appropriate control.
/// </summary>
/// <param name="e"></param>
protected override void OnLoad(EventArgs e)
{
base.OnLoad(e);
int currentTabIndex = 1;
WebControl postBackCtrl = (WebControl)GetControlThatCausedPostBack(Page);
foreach (WebControl ctrl in Panel1.Controls.OfType<WebControl>())
{
ctrl.TabIndex = (short)currentTabIndex;
if (postBackCtrl != null)
{
if (ctrl.TabIndex == postBackCtrl.TabIndex + 1)
ctrl.Focus();
}
currentTabIndex++;
}
}
/// <summary>
/// Retrieves the control that caused the postback.
/// </summary>
/// <param name="page"></param>
/// <returns></returns>
private Control GetControlThatCausedPostBack(Page page)
{
//initialize a control and set it to null
Control ctrl = null;
//get the event target name and find the control
string ctrlName = Page.Request.Params.Get("__EVENTTARGET");
if (!String.IsNullOrEmpty(ctrlName))
ctrl = page.FindControl(ctrlName);
//return the control to the calling method
return ctrl;
}

Thank you for the help, it did get me a little closer. The only thing that was preventing it from working correctly is that my page has some variables which are being carried over from other pages. When the page loads, the override is causing the page to break since it is unable to locate those controls. I was able to fix the issue by adding a HiddenField on the .aspx page and adding the following code to the onload() function:
if (document.getElementById("HiddenField1").value != "") {
var contr = document.getElementById(document.getElementById"HiddenField1").value);
contr.focus();
document.getElementById("HiddenField1").value = "";
}
as well as adding a new function which is called on each of the TextBoxes:
function tabFocus(e) {
document.getElementById("HiddenField1").value = e.id;
}
I ended up not having to make any changes in the code behind. Once again, thank you for the help!

On postback, how can I check which control cause postback in Page_Init event

On postback, how can I check which control cause postback in Page_Init event.
protected void Page_Init(object sender, EventArgs e)
{
//need to check here which control cause postback?
}
Thanks

I see that there is already some great advice and methods suggest for how to get the post back control. However I found another web page (Mahesh blog) with a method to retrieve post back control ID.
I will post it here with a little modification, including making it an extension class. Hopefully it is more useful in that way.
/// <summary>
/// Gets the ID of the post back control.
///
/// See: http://geekswithblogs.net/mahesh/archive/2006/06/27/83264.aspx
/// </summary>
/// <param name = "page">The page.</param>
/// <returns></returns>
public static string GetPostBackControlId(this Page page)
{
if (!page.IsPostBack)
return string.Empty;
Control control = null;
// first we will check the "__EVENTTARGET" because if post back made by the controls
// which used "_doPostBack" function also available in Request.Form collection.
string controlName = page.Request.Params["__EVENTTARGET"];
if (!String.IsNullOrEmpty(controlName))
{
control = page.FindControl(controlName);
}
else
{
// if __EVENTTARGET is null, the control is a button type and we need to
// iterate over the form collection to find it
// ReSharper disable TooWideLocalVariableScope
string controlId;
Control foundControl;
// ReSharper restore TooWideLocalVariableScope
foreach (string ctl in page.Request.Form)
{
// handle ImageButton they having an additional "quasi-property"
// in their Id which identifies mouse x and y coordinates
if (ctl.EndsWith(".x") || ctl.EndsWith(".y"))
{
controlId = ctl.Substring(0, ctl.Length - 2);
foundControl = page.FindControl(controlId);
}
else
{
foundControl = page.FindControl(ctl);
}
if (!(foundControl is IButtonControl)) continue;
control = foundControl;
break;
}
}
return control == null ? String.Empty : control.ID;
}
Update (2016-07-22): Type check for Button and ImageButton changed to look for IButtonControl to allow postbacks from third party controls to be recognized.

Here's some code that might do the trick for you (taken from Ryan Farley's blog)
public static Control GetPostBackControl(Page page)
{
Control control = null;
string ctrlname = page.Request.Params.Get("__EVENTTARGET");
if (ctrlname != null && ctrlname != string.Empty)
{
control = page.FindControl(ctrlname);
}
else
{
foreach (string ctl in page.Request.Form)
{
Control c = page.FindControl(ctl);
if (c is System.Web.UI.WebControls.Button)
{
control = c;
break;
}
}
}
return control;
}

If you need to check which control caused the postback, then you could just directly compare ["__EVENTTARGET"] to the control you are interested in:
if (specialControl.UniqueID == Page.Request.Params["__EVENTTARGET"])
{
/*do special stuff*/
}
This assumes you're just going to be comparing the result from any GetPostBackControl(...) extension method anyway. It may not handle EVERY situation, but if it works it is simpler. Plus, you won't scour the page looking for a control you didn't care about to begin with.

Either directly in form parameters or
string controlName = this.Request.Params.Get("__EVENTTARGET");
Edit: To check if a control caused a postback (manually):
// input Image with name="imageName"
if (this.Request["imageName"+".x"] != null) ...;//caused postBack
// Other input with name="name"
if (this.Request["name"] != null) ...;//caused postBack
You could also iterate through all the controls and check if one of them caused a postBack using the above code.

if (Request.Params["__EVENTTARGET"] != null)
{
if (Request.Params["__EVENTTARGET"].ToString().Contains("myControlID"))
{
DoWhateverYouWant();
}
}

Assuming it's a server control, you can use Request["ButtonName"]
To see if a specific button was clicked: if (Request["ButtonName"] != null)

An addition to previous answers, to use Request.Params["__EVENTTARGET"] you have to set the option:
buttonName.UseSubmitBehavior = false;

To get exact name of control, use:
string controlName = Page.FindControl(Page.Request.Params["__EVENTTARGET"]).ID;