We Keep Coding

Method with generic and multiple parameters

I want to enable/disable controls in a Windows Forms application according to the user privileges.
Initially I thought of writing a method in each form class that would check the user credentials and then enable/disable its controls. But then I realized I could (maybe) create a static class method which would take the form as a parameter and do the job.
So I started writing it, presuming that sometimes I would like to enable the controls of just one or two panels, instead of the whole form. So, I need the parameters to be:
a varying number of panels and/or
a form class.
My difficulties with this task is that I'm getting an error trying to make the panels argument varying, and I have no idea how to set a parameter that could take any form class. All my form classes obviously inherits from Form generic class, but I don't know how to apply this.
Here's what I got:
public static void Enable(TableLayoutPanel[] containers = null)
{
if (MyOF.isEnabled)
{
return;
}
else
{
try
{
foreach (TableLayoutPanel table in containers)
{
foreach (Control control in table.Controls)
{
control.Enabled = false;
}
}
}
catch (NullReferenceException)
{
}
}
}

If we remember that the Form class derives from Control (indirectly, by deriving from ContainerControl which derives from ScrollableControl, which derives from Control), and the Enabled property belongs to the Control class, we can write a method that will enable any control's children (including the Form or TableLayoutPanel controls), since the Controls collection also belongs to the Control class:
public static void EnableChildren(Control control, bool enabled = true)
{
foreach (Control child in control.Controls)
{
child.Enabled = enabled;
}
}
And then if we also want to be able to use this with a collection of controls (as in your example), we can write an overload that takes a collection:
public static void EnableChildren(IEnumerable<Control> controls = null,
bool enabled = true)
{
if (controls == null) return;
foreach (var control in controls)
{
EnableChildren(control, enabled);
}
}
Now we can use this with a Form or a collection of TableLayoutPanel controls (or any control that has controls in it's Controls collection).
Examples of usage:
var myForm = new Form1();
EnableChildren(this); // 'this' is the current form
EnableChildren(myForm); // a separate instance of a form control
EnableChildren(tableLayoutPanel1, false); // A single TableLayoutPanel control
var tableLayoutPanels = new [] {tableLayoutPanel1, tableLayoutPanel2, tableLayoutPanel3};
EnableChildren(tableLayoutPanels); // An array of tableLayoutPanel controls

One of the simple ways I can think about what you are trying to do, is this. Let me get away for a sec here. I worked on projects where all form controls were built from Metadata. And meta came with licensing info. So, when control was placed where it should, it also was disabled or set read-only based on Metadata but the whole feature would be hidden if licensing info was restricting access to it. Coming back to your approach, this is not a bad approach and I see that this is can be done. And it can be done in 2 ways, (quickly from my head).
Use user controls as surface for the components you want to enable/disable. Create an interface
public interface IDisableableControl // make your fine name, no methods needed - marker interface
. . . . .
public class MyFineUserControl : UserControl, IDisableableControl
And in your static method that you're going to write pass the form, and find all controls that implement this interface and work them the way you want.
2.
Similarly, you can use property Tag, which is available on each control. With that, you can actually set your complex security object that can come from DB-stored metadata and then you evaluate this object stored in Tag to apply your configuration
Your method needs to be recursive
internal static void SetAllControls(Control parent)
{
// Do something with control, for example parent.Enabled = false
if (parent is IDisableableControl)
{
// here you use your logic, evaluate your parent you're dialing with and
// enable/disable correspondingly
parent.Enabled = false;
return;
}
foreach(var c in parent.Controls)
SetAllControls(c);
}
In real life, your TOP parent will be a form and will not need to be disabled, but it's certain children will. In fact, most of the time, once you found a UserControl which implements IDisableableControl that should be end of line, means, you don't need to go into children controls as they all sit on this parent and all will be disabled

I manage to accomplish what I was trying to do with the code below, which is pretty much a blend of all the helpful answers I got:
public static void EnableContainer(params Control[] containers)
{
if(containers.Count() == 0) { return; }
if (MyOF.isEnabled)
{
return;
}
else
{
try
{
foreach (var container in containers)
{
foreach (Control control in container.Controls)
{
control.Enabled = false;
}
}
}
catch (NullReferenceException)
{
}
}
}
public static void EnableForm<form>(form f) where form : Form
{
if (MyOF.isEnabled)
{
return;
}
else
{
foreach(Control control in f.Controls)
{
control.Enabled = false;
}
}
}
The community is welcome to suggest improvements as I am far from being a professional programmer. Thanks everyone once again.

C# LoadControl() (.ascx) and add into "this" rather than sub control

I'm good with Loading the control, using the LoadControl("~/vitrualPath"), so I have:
UserControl ctrl = (UserControl)LoadControl("~/controls/someControl.ascx");
this.Controls.Add(ctrl);
//plcCtrl.Controls.Add(ctrl);
The trouble is that I wish to then loop through all the controls in the usercontrol:
foreach (Label c in this.Controls.OfType<Label>())
{
// It's a label for an input
if (c.ID.Substring(0, 8) == "lblInput")
{
// Do some stuff with the control here
}
}
However, the added controls aren't part of this, but part of ctrl
Is there a way I can add the contents of the loaded control to this or a way to loop through both this and ctrl in one hit?

If you simply want to loop through both top-level labels and labels in ctrl, try this.Controls.Concat(ctrl.Controls).OfType<Label>() in your foreach loop.
You can also move your if into a LINQ Where call:
.Where(l => l.ID.Substring(0, 8) == "lblInput")

By using a recursive function you don't need to worry about controls within sub levels/ containers. Something like this should be OK (all you need to do is to pass the top level control along with the id substring that you are interested in). So if the conditions are met it will do whatever you have intended to do with the control and at any sub level.
public void ProcessControl(Control control, string ctrlName)
{
foreach (Label c in control.Controls.OfType<Label>())
{
// It's a label for an input
if (c.ID.Substring(0, 8) == ctrlName)
{
// Do some stuff with the control here
}
}
foreach (Control ctrl in control.Controls)
{
ProcessControl(ctrl, ctrlName);
}
}

You should write a recursive method that starts looping the controls in this.Controls and goes down the tree of controls. It will then also go in your user control and find your labels.

I don't think there is a way to loop through both like you want.
You can easily create a method that receives a Control as parameter and iterate though its controls. Something like this:
void Function(Control control)
{
foreach (Label c in control.Controls.OfType<Label>())
{
// It's a label for an input
if (c.ID.Substring(0, 8) == "lblInput")
{
// Do some stuff with the control here
}
}
}

You should be able to access the controls inside the user control by accessing the this.Controls[index].Controls I think, however it kind of depends what you are trying to achieve? Their might be a cleaner way of doing what you are trying to do?

Checking Multiple textbox if they're null or whitespace

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);

Actual Element That Lost Focus

I am working on an application that has a GridView item on an ASP.net page which is dynamically generated and does a partial post-back as items are updated within the grid-view. This partial post-back is causing the tab indices to be lost or at the very least ignored as the tab order appears to restart. The grid view itself already has the pre-render that is being caught to calculate the new values from the modified items in the grid-view. Is there a way to get what element had the focus of the page prior to the pre-render call? The sender object is the grid-view itself.

You can try using this function, which will return the control that caused the postback. With this, you should be able to reselect it, or find the next tab index.
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;
}
Here's an instance where I had dynamically generated inputs that updated totals via AJAX on change. I used this code to determine the next tab index, based on the tab index of the control that caused the postback. Obviously, this code is tailored to my usage, but with some adjustments I think it could work for you as well.
int currentTabIndex = 1;
WebControl postBackCtrl = (WebControl)GetControlThatCausedPostBack(Page);
foreach (PlaceHolder plcHolderCtrl in pnlWorkOrderActuals.Controls.OfType<PlaceHolder>())
{
foreach (GuardActualHours entryCtrl in plcHolderCtrl.Controls.OfType<GuardActualHours>())
{
foreach (Control childCtrl in entryCtrl.Controls.OfType<Panel>())
{
if (childCtrl.Visible)
{
foreach (RadDateInput dateInput in childCtrl.Controls.OfType<RadDateInput>())
{
dateInput.TabIndex = (short)currentTabIndex;
if (postBackCtrl != null)
{
if (dateInput.TabIndex == postBackCtrl.TabIndex + 1)
dateInput.Focus();
}
currentTabIndex++;
}
}
}
}
}

Iterating through textbox controls in a panel C#

I have seen many others with similar problems but I cannot find the flaw in my logic here. Any help would be greatly appreciated.
I have a Panel which I have added numerous label and textbox controls to, ie:
myPanel.Controls.Add(txtBox);
These controls are created and added in a method called previous to the iteration method.
I want to iterate through each textbox and use its Text property as a parameter in another method but I am not having any luck. Here is my attempt to iterate:
public void updateQuestions()
{
try
{
foreach (Control c in editQuestionsPanel.Controls)
{
if (c is TextBox)
{
TextBox questionTextBox = (TextBox)c;
string question = questionTextBox.Text;
writeNewQuestionToTblQuestions(question);
}
}
}
catch (Exception err)
{
Console.WriteLine(err.Message);
}
}
The problem I am having is that the controls are not in the Panel when I arrive at this updateQuestions() method. Here is the process involved:
A commandButton is clicked and the questions are read from a DB, for each question a method is called which adds 2 labels and a textbox to editQuestionsPanel.Controls. This panel is inside a PlaceHolder which is then made visible.
When a button inside the PlaceHolder is clicked, the updateQuestions() method is called and the editQuestionsPanel.Controls.Count = 1. As there are approx 12 questions in the DB it should be around 36. The one control inside the Panel is of type:
System.Web.UI.LiteralControl
It contains no controls.
I am sure that somwhere in the lifecycle the Panel's controls are being cleared but I do not know how to step thru the life cycle. I have a Page_load method which is called as soon as a button is clicked but once the button which calls updateQuestions() is clicked the editQuestionsPanel.Controls.Count is already back to 1 so it must be cleared before this but I do not know how to correct this...
Any help you can give to help me solve this would be greatly appreciated - its killing me!

This selects from collection controls only that which are of type TextBox.
(the same as control is TextBox or (control as TextBox) != null)
If controls are contained in editQuestionsPanel.Controls:
using System.Linq;
IEnumerable<TextBox> textBoxes = editQuestionsPanel.Controls.OfType<TextBox>();
foreach (TextBox textBox in textBoxes)
{
// do stuff
}
To select all child controls use next extension method:
public static IEnumerable<T> GetChildControls<T>(this Control control) where T : Control
{
var children = control.Controls.OfType<T>();
return children.SelectMany(c => GetChildControls<T>(c)).Concat(children);
}
Using:
IEnumerable<TextBox> textBoxes = editQuestionsPanel.GetChildControls<TextBox>();

When you add controls dynamically, you need to do that on every request - asp.net doesn't do that for you!
Add the controls in the Init or Load phase, then they will get populated with the postback values.

A frequently made mistake: Container.Controls only contains the first level child controls in this container. That is: TextBox1 in PanelA, PanelA in PanelB, you can't get TextBox1 in PanelB.Controls.
My solution is to write an extension method:
public static IEnumerable<Control> AllControls(this Control ctl)
{
List<Control> collection = new List<Control>();
if (ctl.HasControls())
{
foreach (Control c in ctl.Controls)
{
collection.Add(c);
collection = collection.Concat(c.AllControls()).ToList();
}
}
return collection;
}
Now TextBox1 is in PanelB.AllControls(). To filter all controls with type, using PanelB.AllControls().OfType<TextBox>()

If the other answers don't help, try doing your code but add recursivity. Your code would not work if it's editQuestionsPanel => Panel => Textbox

You can do something like this instead:
var questions = from tb in editQuestionsPanel.Controls.OfType<TextBox>()
select tb.Text;
foreach(var question in questions)
{
writeNewQuestionToTblQuestions(question);
}

Try this
int Count = 0;
foreach (Control ctr in Panel1.Controls)
{
if (ctr is TextBox)
Count++;
}