Example code:
var div = new HtmlGenericControl("div");
div.Controls.Add(new Literal() { ID = "litSomeLit" });
var lit = (Literal)div.FindControl("litSomeLit");
Assert.IsNotNull(lit);
This code fails the assert, because lit is null. Debugging shows that div.Controls definitely contains a literal with ID of "litSomeLit." My questions are "Why?" and "Is there any way to get a control of a specific ID without doing a recursive search of div.Controls[] by hand one element at a time?"
The reason I'm doing things this way is that my actual application is not so straightforward- a method I'm writing is given a complex control with several subcontrols in a number of possible configurations. I need to access a specific control several layers down (eg, the control with ID "txtSpecificControl" might be at StartingControl.Controls[0].Controls[2].Controls[1].Controls[3]). Normally I could just do FindControl("txtSpecificControl"), but that does not seem to work when the controls were just dynamically created (as in the above example code).
Near as I can tell, there is no way to do what I'm trying to accomplish without adding the control to the page. If I had to guess, I'd say that FindControl uses the UniqueID property of the control, which generally contains the IDs of all the controls above the current one (eg OuterControlID$LowerControlId$TargetControlID). That would only get generated when the control actually gets added to the page.
Anyway, here's an implementation of recursive depth-first-search FindControl that'll work when the control is not attached to the page yet:
public static Control FindControl(Control parent, string id)
{
foreach (Control control in parent.Controls)
{
if (control.ID == id)
{
return control;
}
var childResult = FindControl(control, id);
if (childResult != null)
{
return childResult;
}
}
return null;
}
Change your code to
var div = new HtmlGenericControl("div");
Page.Controls.Add(div);
div.Controls.Add(new Literal() { ID = "litSomeLit" });
var lit = (Literal)div.FindControl("litSomeLit");
As far as i know FindControl only works when the control is in the visual tree of the page.
When you confirmed that the control was in the Controls collection, did you do that by inspecting the collection directly? FindControl() may not work in this context.
When you debug the test, is the var lit null? If so, you may have to access the member by item index instead of using the FindControl() method.
Related
I have an ASP.NET Web Forms page childPage.aspx with masterPage.aspx as the master page. The childPage.aspx has a user control (userControl.ascx) control defined on it. Now, I am trying to access the controls on childPage.aspx from within the user control. I have tried a handful of different approaches:
HtmlContainerControl ProductMenu = (HtmlContainerControl)Page.FindControl("ProductMenu");
HtmlContainerControl ProductMenu = (HtmlContainerControl)this.Page.FindControl("ProductMenu");
HtmlContainerControl ProductMenu = (HtmlContainerControl)Parent.FindControl("ProductMenu");
HtmlContainerControl ProductMenu = (HtmlContainerControl)this.Parent.parent.FindControl("ContaintHolder").FindControl("ProductMenu")
In above code, ProductMenu is the id of the <div runat="server" /> on childPage.aspx. Now, I am trying to access it from within my user control, but that fails to return the div.
Please help me out. How should I do this? Thanks in advance.
The reason this doesn't work is likely because the FindControl() method is not recursive. This is called out in the MSDN documentation:
This method will find a control only if the control is directly contained by the specified container; that is, the method does not search throughout a hierarchy of controls within controls.
So, for instance, Page.FindControls() will only search for controls listed in the Page.Controls collection; it won't search the Controls collection of each of those controls. As such, Page.FindControl() would only work if the ProductMenu were at the top-level of your ASPX page; if it is instead nested within, for instance, a Panel control then this code won't work.
To resolve this, you'll need to write a recursive function to crawl the control tree. For instance:
public Control FindControl(Control parentControl, string controlName) {
foreach (var childControl in parentControl.Controls) {
if (childControl.Id == controlName) return childControl;
var foundControl = FindControl(childControl, controlName);
if (foundControl != null) return childControl;
}
return null;
}
In your case, assuming you'll always be looking for an instance of an HtmlContainerControl, you could even validate the type and return a strongly typed object, should you choose. That said, if you want to keep it strongly typed while still supporting different types, you could instead use a generic:
public T FindControl<T>(Control parentControl, string controlName) where T : Control {
foreach (var childControl in parentControl.Controls) {
if (childControl.Id == controlName) return childControl;
var foundControl = FindControl<T>(childControl, controlName);
if (foundControl != null && foundControl is T) return childControl;
}
return null;
}
In addition, if you'll need to do this repeatedly, you might add this as an extension method to the Page class so it's easily accessible on multiple pages.
I have a form where I have lots of textboxes and all of them are required to be filled out. In C# how do I actually if check there are group of fields having a null or whitespace?
I am familiar with string.isNullOrWhiteSpace(string here) but I don't want to do multiple if statements of that, it would result in a bad code.
I am trying to avoid something like this
if(string.isNullOrWhiteSpace(string here)
|| string.isNullOrWhiteSpace(string here)
|| string.isNullOrWhiteSpace(string here))
{
// do something
}
Are there fix for this type of bad code?
You can query the controls collection of the form (or relevant container) and filter for textboxes and further query to see if any are empty (none should really have null values). Example:
var emptyTextboxes = from tb in this.Controls.OfType<TextBox>()
where string.IsNullOrEmpty(tb.Text)
select tb;
if (emptyTextboxes.Any())
{
// one or more textboxes are empty
}
You can do effectively the same thing using the fluent syntax.
bool isIncomplete = this.Controls.OfType<TextBox>().Any(tb => string.IsNullOrEmpty(tb.Text));
if (isIncomplete)
{
// do your work
}
For this code, you should be working with at least Visual Studio 2008 / C# 3 / .NET 3.5. Your project needs to have a reference to System.Core.dll (should have one by default) and you need a using System.Linq; directive in the class file.
Based upon your comments, consider another method if you are having trouble understanding or working with the linq version. You can certainly do this in an explicit loop (the Linq code will ultimately be a loop as well). Consider
bool isIncomplete = false;
foreach (Control control in this.Controls)
{
if (control is TextBox)
{
TextBox tb = control as TextBox;
if (string.IsNullOrEmpty(tb.Text))
{
isIncomplete = true;
break;
}
}
}
if (isIncomplete)
{
}
Finally, this code is written as if all of the textboxes are in a single container. That container might be the form, a panel, etc. You will need to point to the appropriate container (eg., instead of this (the form) it might be this.SomePanel). If you are working with controls that are in multiple and perhaps nested containers, you will need to do more work to find them programmatically (recursive searching, explicit concatenation, etc.) or you might just preload the references into an array or other collection. For example
var textboxes = new [] { textbox1, textbox2, textbox3, /* etc */ };
// write query against textboxes instead of this.Controls
You said you have multiple GroupBox controls. If each GroupBox is loaded onto the form and not nested in another control, this may get you started.
var emptyTextboxes = from groupBox in this.Controls.OfType<GroupBox>()
from tb in groupBox.Controls.OfType<TextBox>()
where string.IsNullOrEmpty(tb.Text)
select tb;
That depends on what you consider "bad code." Depending on your requirements what text boxes are required to be filled out can vary. Further, even if all of the fields are required all of the time you still want to give friendly error messages letting people know which field they didn't fill out. There a variety of approaches to solving this issue depending on how you are rendering your form. Since you haven't specified any here's a very direct method for doing so.
var incompleteTextBoxes = this.Controls.OfType<TextBox>()
.Where(tb => string.IsNullOrWhiteSpace(tb.Text));
foreach (var textBox in inCompleteTextBoxes)
{
// give user feedback about which text boxes they have yet to fill out
}
Yet another solution.
This will recursively travel the whole control Tree , and Check for null or empty text in all of the textboxes.
caveat -
If you have some fancy controls not inheriting from the standard Winforms textbox - check will not be performed
bool check(Control root,List<Control> nonFilled)
{
bool result =true;
if (root is TextBox && string.isNullOrEmpty(((TextBox)root).Text) )
{
nonFilled.Add(root);
return false;
}
foreach(Control c in root.Controls)
{
result|=check(c,nonFilled)
}
return result;
}
Usage :
List<Control> emptytextboxes=new List<Control>()
bool isOK=check(form, emptytextboxes);
I've got a web page where I am dynamically creating controls during Page_Load event (this is done so because I do not know how many controls I will need until session is active and certain variables are accessible)
I need to be able to loop through these controls to find Checkbox when a button click is processed. Looping through the Form.Controls does not appear to be sufficient. I would think that Request.Form might work but it does not appear to be accessible in my C# block?
What should code for Request.Form look like? OR
Has anyone done this before with dynamically created controls?
Any insight is appreciated.
Simplified Example from MSDN:
var myControl = FindControl("NameOfControl");
if(myControl != null)
{
//do something
}
else
{
//control not found
}
Hope this helps! ;)
Your controls will be accessible trough the Controls collection of their immediate parent. Unless you add them like Page.Form.Controls.Add (myControl);, you won't find it in Page.Form.Conttrols. If you add them to a place holder, you must find them in thePlaceHolder.Controls.
LinkButton myDynamicLinkButton = new myDynamicLinkButton ();
myDynamicLinkButton.ID = "lnkButton";
myPlaceHolder.Controls.Add (myDynamicLinkButton);
//........
LinkButton otherReferenceToMyLinkButton = myPlaceHolder.FindControl ("lnkButton");
As #David said in his comment, you should probably think about using a Repeater instead. It would probably simplify your case a lot.
Since the controls might be nested in other controls, you need to search recursively. You can use this method to find the control:
public 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;
}
And you can implement it this way:
CheckBox check = FindControlRecursive(Page.Form, "CheckBox1");
You should have access to Request["xyz"] anywhere in your aspx.cs code. You can either find control as described above and read it's value or do so directly from Request using the Control.UniqueID property. For example if it's a checkbox that's within the repeater then the UniqueID would look like dtgData$ctl02$txtAmount
Thanks for the insight guys. I kind of took the discussion and ran with it and found my solution that worked best for me.
foreach(String chk in Request.Form)
{
if (chk.Contains("chkRemove"))
{
int idxFormat = chk.LastIndexOf("chkRemove");
objectname = chk.Substring(idxFormat);
}
}
Turned out really all I needed was the name. The string contained a number at the end which was needed to determine a position of datatable items. Thanks for the advice!
I've written a web user control which I want to be able to drop into the markup for either aspx pages or other web user controls.
I need my user control to be able to easily and efficiently work out if its inside another user control or an aspx page. My initial idea is to do it recursively with checks on the Parent property - continue looking up the nesting hierarchy until I find either a web form or a user control - but I'm not sure this the best way of going about this.
Can you suggest an easier way? Thanks.
Recursively check the type of your Parent until Parent.GetType() is either typeof(UserControl) or type(Page)
private bool IsAncestorTypeOf(Control c, params Type[] typesToCheck)
{
var parent = c.Parent;
if (parent == null) return false;
if (typesToCheck.Contains(parent.GetType())) return true;
return IsAncestorTypeOf(parent, typesToCheck);
}
Or the same without recursion
private bool IsAncestorTypeOf(Control c, params Type[] typesToCheck)
{
var parent = c.Parent;
while (true)
{
if (parent == null) return false;
if (typesToCheck.Contains(parent.GetType())) return true;
parent = parent.Parent;
}
}
Call it like
var isAncestorPageOrUserControl = IsAncestorTypeOf(this, typeof(Page), typeof(UserControl));
or
var isAncestorPage = IsAncestorTypeOf(this, typeof(Page));
var isAncestorUserControl = IsAncestorTypeOf(this, typeof(UserControl));
Generally, components should be unaware of their arbitrary containers, although the containers must know their components (unless it's a strong dependency situation like list items are always in a list type and you can make a strong two way relationship). However it sounds like you are reaching out into the general surroundings. You might find many cases to code for doing this and accidentally miss others.
By making the user control aware of its surroundings and the larger world you may be introducing dependencies that make your control less reusable and harder to maintain.
If something the control needs is outside of itself, you might move toward composition by forcing the developer to provide a reference to the needed thing on a property of your user control. This is the way, for example, that validation controls in ASP.NET do it, to reference an external control to validate by id.
Of course what I specified is practical only some of the time. Is there a specific reason or edge case why you need to make your user control look around itself, or can you get away with providing instructions to the developer about where the control should be used?
This should work:
C#
bool inPage = (this.NamingContainer == this.Page);
VB.NET
Dim inPage as Boolean = Me.NamingContainer is Me.Page
Edit: it seems to be not as simple as i hoped. If the usercontrol resists in a control like a GridViewRow, the NamingControl of it would be the Row and not the Page.
This takes it into account:
C#
public static bool isControlInPageOruserControl(Control uc)
{
bool inPage = uc.NamingContainer is Page;
if (inPage) {
return true;
} else if (uc.NamingContainer is UserControl) {
return false;
} else {
return isControlInPageOruserControl(uc.NamingContainer);
}
}
VB.NET:
Public Shared Function isControlInPageOruserControl(ByVal uc As Control) As Boolean
Dim inPage As Boolean = TypeOf uc.NamingContainer Is Page
If inPage Then
Return True
ElseIf TypeOf uc.NamingContainer Is UserControl Then
Return False
Else
Return isControlInPageOruserControl(uc.NamingContainer)
End If
End Function
I'm trying to fix this ugly code.
RadGrid gv = (RadGrid) (((Control) e.CommandSource).Parent.Parent.Parent.Parent.Parent);
I often need to find the first grid that is the parent of the parent of... etc of a object that just raised an event.
The above tends to break when the layout changes and the number of .Parents increase or decreases.
I don't necessarily have a control Id, so I can't use FindControl().
Is there a better way to find the 1st parent grid?
Control parent = Parent;
while (!(parent is RadGrid))
{
parent = parent.Parent;
}
If you really have to find the grid, then you might something like this:
Control ct = (Control)e.CommandSource;
while (!(ct is RadGrid)) ct = ct.Parent;
RadGrid gv = (RadGrid)ct;
But maybe you can explain why you need a reference to the grid? Maybe there is another/better solution for your problem.
I'm not familiar with the API that you are using, but can you do something like:
Control root = ((Control)e.CommandSource);
while(root.Parent != null)
{
// must start with the parent
root = root.Parent;
if (root is RadGrid)
{
// stop at the first grid parent
break;
}
}
// might throw exception if there was no parent that was a RadGrid
RadGrid gv = (RadGrid)root;
If you have control of the Parent's code, you could use simple recursion to do it, I'd think. Something like:
public Control GetAncestor(Control c)
{
Control parent;
if (parent = c.Parent) != null)
return GetAncestor(parent);
else
return c;
}
I make no claims as to how well that will work, but it should get the idea across. Navigate up the parent chain as far as it goes until there is no parent, then return that object back up the recursion chain. It's brute force, but it will find the first parent no matter how high it is.