Develop Reference

Creating static Windows.Forms.Control

I have a project to which I delegate the function of creating a library of (static)? classes used in all my other projects. It is referenced via solution in these cases.
For instance, I have an extension which creates checkboxes within a given GroupBox's panel, and that works great:
public static void PreencheCheckboxesPanel(this Panel p, List<CheckBox> listaCheckBoxs) {
var count = 0;
listaCheckBoxs.ForEach(
i => {
i.Location = new Point(10, 10 + ((count) * 25)); //"dynamic" and not-so-effective resizing here
i.AutoSize = true;
count++;
});
p.Controls.AddRange(listaCheckBoxs.ToArray());
}}
Problem is, I need to insert a static checkbox on the top of the list, which will receive a method to (un)?check all the checkboxes below.
So my code will become
internal static CheckBox CKB_ancora = new CheckBox(){};
public static void PreencheCheckboxesPanel(this Panel p, List<CheckBox> listaCheckBoxs) {
var count = 0;
if (adicionaAncora) {
CKB_ancora.Text = textoAncora;
CKB_ancora.CheckedChanged += (sender, args) => {
ChecaCheckBoxes(p, CKB_ancora.Checked);
};
listaCheckBoxs.Insert(0, CKB_ancora);
}
listaCheckBoxs.ForEach(
i => {
i.Location = new Point(10, 10 + ((count) * 25)); //"dynamic" and not-so-effective resizing here
i.AutoSize = true;
count++;
});
p.Controls.AddRange(listaCheckBoxs.ToArray());
}}
where ChecaCheckBoxes is another
public static void ChecaCheckBoxes(this Panel b, bool checkStatus = true) {
var listaCheckBoxs = (from Control c in b.Controls where c is CheckBox select (CheckBox)c).ToList();
listaCheckBoxs.ForEach(
i => {
i.Checked = checkStatus;
});
}
and CKB_ancora needs to be a solution-wide recognized object.
The reason? I have another extension named GetSelectedCheckBoxes which will be used to return all the checked ... ah... checkboxes within the groupbox. And, in order to make sure that the "anchor" (I call it like this, since I don't have a name to a (un)?check-all checkbox) won't be returned as well.
If I run this code, it will compile, but... will run accross an InvalidOperationException at Application.SetCompatibleTextRenderingDefault, right at Main(); Apparently, a control cannot be created/instantied before this method is run at mainpoint, which is the exact definition of "static".
Question: Knowing that I NEED a way to keep this particular check solution-wide visible... How do I do it?

Unfortunately, you have not provided a good, minimal, complete code example, and lacking enough context it is very hard to provide good, specific advice.
That said, it seems that somewhere in this static class of yours, you have a field named CKB_ancora, and you are probably initializing it using a field initializer, possibly like this:
private CheckBox CKB_ancora = new Checkbox();
And having done this, you are finding that when the class is initialized (typically on the first time something in the class is accessed at runtime), that happens too soon and an exception is thrown.
Assuming that's correct, then it seems to me that most obvious and simplest "fix" is to initialize the object lazily. For example:
private Lazy<CheckBox> _ckb_ancora =
new Lazy<CheckBox>(() => new CheckBox());
private CheckBox CKB_ancora { get { return _ckb_ancora.Value; } }
That will wrap the object storage in a property, which in turn uses an instance of Lazy<T> to defer initialization until the first time any code actually tries to access it.
Now, that said, I'm not very enamored of your approach here, with a static member that is used in some instantiated object. What if someone using your library wants to use the code with two or more Panel instances? A Control (including a CheckBox) can't be a child of more than one other Control at a time, so having a single static instance of the Control is just not going to work.
IMHO, it would probably be better to instead use some identifying feature such as the Name or Tag property of the CheckBox to handle the control appropriately (e.g. such as filtering it out of enumerations).
For example:
public static void PreencheCheckboxesPanel(this Panel p, List<CheckBox> listaCheckBoxs) {
var count = 0;
if (adicionaAncora) {
CheckBox CKB_ancora = new CheckBox();
CKB_ancora.Text = textoAncora;
CKB_ancora.Name = "CKB_ancora";
CKB_ancora.CheckedChanged += (sender, args) => {
ChecaCheckBoxes(p, CKB_ancora.Checked);
};
listaCheckBoxs.Insert(0, CKB_ancora);
}
listaCheckBoxs.ForEach(
i => {
i.Location = new Point(10, 10 + ((count) * 25)); //"dynamic" and not-so-effective resizing here
i.AutoSize = true;
count++;
});
p.Controls.AddRange(listaCheckBoxs.ToArray());
}}
And, for example:
public static void ChecaCheckBoxes(this Panel b, bool checkStatus = true) {
var listaCheckBoxs = b.Controls
.OfType<CheckBox>().Where(c => c.Name != "CKB_ancora").ToList();
listaCheckBoxs.ForEach(
i => {
i.Checked = checkStatus;
});
}
That way, when you go to retrieve the list of CheckBox controls, the special one you added at the beginning is ignored.
Even with that, I think the code is still pretty fragile. The above would work better, but IMHO it would probably be even better if you weren't using static members for all of this in the first place. I.e. instead you should design some mechanism that allows you to relate an instance of the helper class to the Panel object it's helping with, so that you can in fact initialize and store per-instance information, without running into problems of order of execution, as well as of limitations of use of the code with just a single client.
Without a better code example, I don't see any good way to offer any specific advice along those lines though.

How to Give back a DataGridView in Winforms

So, I have a project in which I allow editing of a DatagridView in a separate Form. I pass in the DatagridView object and its parent container to the constructor of the new Form.
This works well and I can edit the grid that way. But when I try to give it back by changing its parent back to the original form, I get this error :
Cannot convert type 'System.Windows.Forms.MenuItem' to 'System.Windows.Forms.Control'
Now both MenuItem, and Manual Entry directly inherit from Form.
Here is my code that takes the DataGridView from the original form (which works correctly)
public partial class ManualEntry : Form
{
private Data d;
DataGridView DataView;
MenuItem mi;
public ManualEntry(DataGridView ExcelDisplay, Data d, MenuItem menuItem)
{
InitializeComponent();
//Take the Datagridview from the MenuItem.
DataView = ExcelDisplay;
DataView.Parent = this;
mi = menuItem;
this.d = d;
this.DataView.ColumnHeadersHeightSizeMode = System.Windows.Forms.DataGridViewColumnHeadersHeightSizeMode.AutoSize;
this.DataView.Location = new System.Drawing.Point(15, 76);
this.DataView.Size = new System.Drawing.Size(237, 211);
this.DataView.TabIndex = 5;
this.DataView.CellContentClick += new System.Windows.Forms.DataGridViewCellEventHandler(this.DataView_CellContentClick);
}
Now here is me trying to give it back. and of course it produces the error above.
private void FinishButton_Click(object sender, EventArgs e)
{
//move the datagridview back to the original form and give its old size,shape, and position back.
DataView.Parent = mi;
this.DataView.ColumnHeadersHeightSizeMode = System.Windows.Forms.DataGridViewColumnHeadersHeightSizeMode.AutoSize;
this.DataView.Location = new System.Drawing.Point(12, 167);
this.DataView.Name = "ExcelDisplay";
this.DataView.Size = new System.Drawing.Size(250, 256);
this.DataView.TabIndex = 7;
this.Close();
}
I have also tried casting which does not work either.
DataView.Parent = (System.Windows.Forms.Control)mi;
Update
This shows that MenuItem is a Form as well.
public partial class MenuItem : Form
{

This shows that MenuItem is a Form as well.
Well, you have not convinced the compiler. You can tell from the error message that it thinks that your "mi" variable is a System.Windows.Forms.MenuItem. Do not use .NET class names for your own types, that just makes your life harder to troubleshoot bugs like this. Don't use variable names like "d" either. Choosing good names is a Very Important programmer's job.
The proper way is to preserve the control's Parent property so you can set it back. Roughly:
public partial class ManualEntry : Form
{
private Data DataViewData;
private DataGridView DataView;
private Point DataViewLocation;
private Control DataViewParent;
public ManualEntry(DataGridView ExcelDisplay, Data data)
{
InitializeComponent();
this.DataViewData = data;
this.DataView = ExcelDisplay;
this.DataViewLocation = ExcelDisplay.Location;
this.DataViewParent = ExcelDisplay.Parent;
this.DataView.Parent = this;
// etc...
}
protected override void OnFormClosing(FormClosingEventArgs e) {
base.OnFormClosing(e);
if (!e.Cancel) {
DataView.Parent = this.DataViewParent;
DataView.Location = this.DataViewLocation;
// etc..
}
}
}

Programmatically adding two buttons to each row as it loads

I've created a ListView in a new WPF window and also a function that populates the ListView when it is called. This function just takes the URL of my web server where I've stored the data, increments the "id" and gets the data and stores it in the ListView. Therefore it populates the ListView with a certain number of items.
The problem I'm facing is that I want to add two buttons, ON & OFF, to each ListView item as it gets populated programmatically. i.e, if 16 items are added, I want 2 buttons for each item, and if it's 12 items, the similar procedure. Here's my code:
namespace user_login
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
Window1 W = new Window1();
public MainWindow()
{
InitializeComponent();
}
public void populate()
{
int i;
int num = 16;
for (i = 1; i <= num; i++)
{
string val = Convert.ToString(i);
string currentUrl = "http://xpleria.com/devices.php?query=dev&id=";
string newUrlWithChangedSort = ReplaceQueryStringParam(currentUrl, "id", val);
string result = getcontent(newUrlWithChangedSort);
W.list1.Items.Add(result);
}
}
public string getcontent(string URL)
{
string content = "";
// Get HTML data
WebClient client = new WebClient();
try
{
content = client.DownloadString(URL);
}
catch (Exception)
{
System.Windows.Forms.MessageBox.Show("No Connection detected!!!");
}
return content;
}
public static string ReplaceQueryStringParam(string currentPageUrl, string paramToReplace, string newValue)
{
string urlWithoutQuery = currentPageUrl.IndexOf('?') >= 0
? currentPageUrl.Substring(0, currentPageUrl.IndexOf('?'))
: currentPageUrl;
string queryString = currentPageUrl.IndexOf('?') >= 0
? currentPageUrl.Substring(currentPageUrl.IndexOf('?'))
: null;
var queryParamList = queryString != null
? HttpUtility.ParseQueryString(queryString)
: HttpUtility.ParseQueryString(string.Empty);
if (queryParamList[paramToReplace] != null)
{
queryParamList[paramToReplace] = newValue;
}
else
{
queryParamList.Add(paramToReplace, newValue);
}
return String.Format("{0}?{1}", urlWithoutQuery, queryParamList);
}
private void Button_Click_1(object sender, RoutedEventArgs e)
{
string user = textbox1.Text;
string password = textbox2.Password;
string currentUrl = "http://xpleria.com/login.php?query=login&user=wcam&pass=wireless";
string newUrlWithChangedSort = ReplaceQueryStringParam(currentUrl, "user", user);
string newUrl = newUrlWithChangedSort;
string FinalUrl = ReplaceQueryStringParam(newUrl, "pass", password);
string result= getcontent(FinalUrl);
string value = result.Substring(0, 8);
string invalid = "xpleria0";
string valid = "xpleria1";
if (value.Equals(invalid))
{
System.Windows.MessageBox.Show("The Username and/or Password you have entered is invalid, please try again");
}
else if (value.Equals(valid))
{
string sessionID = result.Substring(8, 32);
System.Windows.MessageBox.Show("HI, WELCOME CLETA");
this.Close();
using (new user_login.loading.PleaseWait(this.Location))
{
W.Show();
populate();
}
}
}
public System.Drawing.Point Location { get; set; }
}
}

I'm going to recommend you take a step back and start giving some serious consideration to organizing your code. I realize this isn't an answer to the question you asked but it is the answer to the question you should be asking.
First of all, all code relating to the retrieval of these items from the URL should be moved into a class of some kind. This class should accept the URL string as a constructor parameter and gather all the appropriate data. You should then create another class which you will use to populate with the data for each individual item and then expose this list. By the time you're done the code in your window should little more complex than:
var ItemsGetter = new ItemsGetter(URL);
foreach(var Item in ItemsGetter.Items)
{
// Populate the ListView
}
Once you're done with that I recommend you create a UserControl. User controls are extremely useful in situations where you need to represent a dynamic number of data entities each with their own set of controls which allow operations to be performed on each one. You should create a UserControl with a label and the two buttons you need. The UserControl's constructor should expect a parameter of the data type you created to represent each one of your classes. From there you can have the buttons operate on the data type as necessary.
Finally, you'll probably need a way to have the UserControl interact with the Window. Say for example one of your buttons is "Delete". You'd probably want the item to disappear from the list once the operation is complete. Don't be tempted to tie in your control with the Window by passing it as a parameter or something. Instead, read up on Action events and learn how you can create an event on the user control which you bind in the foreach loop of the Window when you're populating the list view. When the UserControl has completed the delete operation triggered by the button you can raise the UserControl's event which will prompt the Window to remove the control from the List View.
Last but not least, NAME YOUR CONTROLS.
Hopefully this helps.

Accessing a list of class from within another class - null reference exception

I have a class which creates a list of another class.
which looks like:
class SortItAll
{
Recipient rec;
public List<Recipient> listofRec = new List<Recipient>();
public void sortToClass()
{
while (isThereNextLine()) { //while there is a following line
loadNextLine(); //load it
rec = new Recipient(loadNextPiece(), //break that line to pieces and send them as arguments to create an instance of "Recipient" class
loadNextPiece(),
loadNextPiece(),
loadNextPiece());
listofRec.Add(rec); //add the created instance to my list
}
}
From my Form1 class I call this method (sortToClass()), which by my logic should fill my list with that specific class. Then I want to write the list.count() to a textbox:
public Form1()
{
SortItAll sort = new SortItAll(); //create the instance of the class
sort.sortToClass(); //within which i call the method to fill my list
txt_out.Text = sort.listofRec.Count().ToString(); //writing out its count to a textbox
InitializeComponent();
}
And now my problem is whenever I try to debug, it stops me with a
Nullreference exception pointing to -> "txt_out.Text = sort.listofRec.Count().ToString();" in Form1.
Yet, while debugging I can check the locals, where it states:
sort -> listOfRec -> Count = 4.
What might be the problem?

Put
txt_out.Text = sort.listofRec.Count().ToString(); //writing out its count to a textbox
after InitializeComponent(), since it's created in that method.

You should keep InitializeComponent(); at the top of the method as it creates all the controls on the form. You are probably getting it because you are trying to access control txt_out before it has been created and added to the form.

Dynamically Cast Page.LoadControl in C#

I'm writing some user controls for the first time and I'm wondering if there's a way I can clean up some of my code. (If you'd like more background on what I'm working on, see this question.)
I have a BaseControl class that, basically, parses some XML data and then, depending on what is contained in that data, calls the appropriate UserControl and sends the data on its way. Here's an example:
public partial class BaseControl : User Control
{
protected void Page_Load(object sender, EventArgs e)
{
... //code that parses the data
var renewalDef = effort.Attributes["renewal_def"].Value;
var effortNumber = effort.Attributes["renewal_effort_number"].Value;
if (effortNumber == "1")
{
var effortControl = (NAVLEffort1) Page.LoadControl("~/NAVLSeriesControls/NAVLEffort1.ascx");
effortControl.transactionData = transaction; //'transaction' is a Hashtable object
HtmlContent.Controls.Add(effortControl); //'HtmlContent' is a PlaceHolder control on BaseControl.ascx page
}
if (effortNumber == "2")
{
var effortControl = (NAVLEffort2) Page.LoadControl("~/NAVLSeriesControls/NAVLEffort2.ascx");
effortControl.transactionData = transaction; //'transaction' is a Hashtable object
HtmlContent.Controls.Add(effortControl); //'HtmlContent' is a PlaceHolder control on BaseControl.ascx page
}
if (effortNumber == "3")
{
var effortControl = (NAVLEffort3) Page.LoadControl("~/NAVLSeriesControls/NAVLEffort3.ascx");
effortControl.transactionData = transaction; //'transaction' is a Hashtable object
HtmlContent.Controls.Add(effortControl); //'HtmlContent' is a PlaceHolder control on BaseControl.ascx page
}
// and so on...
}
}
This isn't the actual code I've written, it's just an example of where I could be headed. What I'd like to do is something more like this:
...
var effortControlFileString = string.Format("~/NAVLSeriesControls/{0}Effort{1}.ascx", renewalDef, effortNumber);
var effortControl = (renewalDef + "Effort" + effortNumber) Page.LoadControl(effortControlFileString);
effortControl.transactionData = transaction;
HtmlContent.Controls.Add(effortControl)
...
Any ideas how I can clean this mess up?

Interface
You could have all controls implement a common interface and cast to that.
public interface IMyInterface
{
object TransactionData
{
get;
set;
}
}
Control effortControl = Page.LoadControl(path);
HtmlContent.Controls.Add(effortControl);
IMyInterface obj = (IMyInterface)effortControl;
obj.TransactionData = transaction;
See this working example in an online IDE.
Base Class
You could also use an abstract base class and cast to that type with the same results. You will need to use a base class which inherits from UserControl. This would avoid having two object references (as in my example above) because it can be cast to UserControl.
The example above becomes:
MyCustomControlType c = (MyCustomControlType)Page.LoadControl(path);
HtmlContent.Controls.Add(c);
c.TransactionData = transaction;
If the logic for each control type is different, then you will probably need to cast to each specific type (basically a big if/else block) and deal with each control individually. In other words, if you need to perform different actions based on the type of the control, you will need logic that is type-aware.
For completeness sake I will mention that you could also use the DLR but I would suggest against it. You would be giving up compile-time type safety and performance to reduce a little code.

you can create an interface and add your control to html page.
ex:
private Control _contentControl;
_contentControl = Page.LoadControl("~/Administration/Projects/UserControls/" + controlName);
((IEditProjectControl)_contentControl).ProjectId = ProjectId;
plhContent.Controls.Clear();
plhContent.Controls.Add( _contentControl );
_contentControl.ID = "ctlContent";
Image2.Visible = ((IEditProjectControl)_contentControl).ShowSaveButton;
SaveButton.Visible = ((IEditProjectControl)_contentControl).ShowSaveButton;
((IEditProjectControl)_contentControl).Initialize();