Bassicly im creating a program that reads information from an xml file into a lisbox and allows the user to transfer items in the list box to another listBox.
But i want to some how disallow multiple items from being imported from one listBox to the other. I thought i can somehow do an experession to check if the String already Exists in the listBox.
The reason i want to do this is because the user can click x amount of times in order to import items and it's unproffesional.
Any Help would be appreciated thank you.
private void button1_Click(object sender, EventArgs e)
{
if (!listBox.Items.Exists) // Random Idea which doesnt work
{
listBox2.Items.Add(listBox1.Items[listBox1.SelectedIndex]);
}
}
private void button1_Click(object sender, EventArgs e)
{
if (!listBox.Items.Exists) // Random Idea which doesnt work
{
listBox2.Items.Add(listBox1.Items[listBox1.SelectedIndex]);
}
}
That will work actually, but you need to use the Contains method. However, you may be missing one crucial point.
What type of items are you using to populate your ListBox? Exists will call .Equals which, by default, uses reference equality. So, if you need to filter based on value, you need to override .Equals for your type and change the semantics.
For example:
class Foo
{
public string Name { get; set; }
public Foo(string name)
{
Name = name;
}
}
class Program
{
static void Main( string[] args )
{
var x = new Foo("ed");
var y = new Foo("ed");
Console.WriteLine(x.Equals(y)); // prints "False"
}
}
However, if we override .Equals to provide value type semantics...
class Foo
{
public string Name { get; set; }
public Foo(string name)
{
Name = name;
}
public override bool Equals(object obj)
{
// error and type checking go here!
return ((Foo)obj).Name == this.Name;
}
// should override GetHashCode as well
}
class Program
{
static void Main( string[] args )
{
var x = new Foo("ed");
var y = new Foo("ed");
Console.WriteLine(x.Equals(y)); // prints "True"
Console.Read();
}
}
And now your call to if(!listBox.Items.Contains(item)) will work as you intended it to. However, if you wish it to continue working you will need to add the item to both listboxes, not just listBox2.
This should do it for you...
private void button1_Click(object sender, EventArgs e)
{
if (!ListBox.Items.Contains(listBox1.SelectedItem)) // Random Idea which doesnt work
{
listBox2.Items.Add(listBox1.SelectedItem);
}
}
Related
I want to access array from one class to another class because my end-user enter the name list on one class. That list store into array in the same class. Then that name list access from another class. I'm not getting any errors in compile time. only I'm getting a run time error. I'm literally sorry to all coz I'm absolutely noob :(
public partial class custom : Form //class one which is end user enter the name list
{
public string PresentValue;
public string NormalValue;
public string[] PValue = new string[50];//public array
public string[] NValue = new string[50];//public array
}
public static int PresentArray = 0;// this line is used to increment the array index
private void cstmsvbtn_Click(object sender, EventArgs e)//this line enter the user namelist
{
PresentValue = cstmtst1.Text + "_PV";//concatinate '_PV'
NormalValue = cstmtst1.Text + "_NV";//concatinate '_NV'
PValue[PresentArray] = PresentValue;
NValue[PresentArray] = NormalValue;
PresentArray++;
}
public partial class print : Form // class to which is end user want to access that name list
{
custom customarray = new custom();// I instantiate the custom cass object
private void button1_Click(object sender, EventArgs e)//when i press this button message box show an empty white box only
{
MessageBox.Show(CustomArray.PValue[0],CustomArray.NValue[0]);
}
}
This is a common requirement and there are many ways to achieve this outcome (some of which might be considered "hacky"). Things I don't recommend:
Changing visibility to public for data fields that should be private
Creating tight dependencies of one form to the implementation details of another.
Creating "global" variables using the static keyword.
Since you claim to be a "noob" I'd like to suggest learning about the event keyword and using Events to communicate between forms. Yes, there is a small learning curve here, but chances are you'll use this a lot and it will be a good investment. I put a link in the Comments section so you can clone or browse this example and see if it does what you want it to (I recommend setting debugger break points so you can see why it does what it does).
What you have (according to your post) is a print form and a custom form. And though you don't really say, this example will have a MainForm that can show the other two:
PrintForm
The PrintForm requires the NValue and PValue arrays to do its printing. By declaring an event named ArrayRequest we give it the ability to request these arrays. Importantly, this class doesn't need to have any knowledge of where this information might be coming from.
public partial class PrintForm : Form
{
public PrintForm() => InitializeComponent();
This is how the class can initiate the request
public event ArrayRequestEventHandler ArrayRequest;
protected virtual void OnArrayRequest(ArrayRequestEventArgs e)
{
ArrayRequest?.Invoke(this, e);
}
When the button is clicked, try and get the information by callingOnArrayRequest
private void buttonShowArray_Click(object sender, EventArgs e)
{
ArrayRequestEventArgs req = new ArrayRequestEventArgs();
OnArrayRequest(req);
if(req.Count == 0)
{
MessageBox.Show("Invalid Request");
}
else
{
String[] allValues =
Enumerable.Range(0, req.Count)
.Select(index => $"{req.NValue[index]} | {req.PValue[index]}")
.ToArray();
MessageBox.Show(
text: string.Join(Environment.NewLine, allValues),
caption: "All Values"
);
}
}
}
// Defined outside the PrintForm class
public delegate void ArrayRequestEventHandler(Object sender, ArrayRequestEventArgs e);
public class ArrayRequestEventArgs : EventArgs
{
public int Count { get; set; }
public string[] PValue { get; set; }
public string[] NValue { get; set; }
}
CustomForm
The CustomForm as shown in your post is the class that contains the arrays.
public partial class CustomForm : Form
{
public CustomForm()
{
InitializeComponent();
}
We give this class the ability to fulfill a request for the arrays.
internal void ArraysRequested(object sender, ArrayRequestEventArgs e)
{
e.Count = _presentArray;
e.NValue = _nValue;
e.PValue = _pValue;
}
The data held in this class should be private.
// These should all be private
// See naming conventions: https://stackoverflow.com/a/17937309/5438626
// Set up visual studio to do this automatically: https://ardalis.com/configure-visual-studio-to-name-private-fields-with-underscore/
private string _normalValue;
private string _presentValue;
private int _presentArray = 0;
private string[] _pValue = new string[50];//public array
private string[] _nValue = new string[50];//public array
private void cstmsvbtn_Click(object sender, EventArgs e)
{
_presentValue = $"{cstmtst1.Text}_PV"; //concatinate '_PV'
_normalValue = $"{cstmtst1.Text}_NV"; //concatinate '_NV'
// Make sure index doesn't exceed the size of the array
if ((_presentArray < _pValue.Length) && (_presentArray < _nValue.Length))
{
_pValue[_presentArray] = _presentValue;
_nValue[_presentArray] = _normalValue;
_presentArray++;
}
else MessageBox.Show("Array is Full");
Text = $"Custom: Count={_presentArray}";
cstmtst1.Text = $"Hello {_presentArray + 1}";
}
}
MainForm
It is the MainForm class that oversees the operations and "knows" how the forms should interact. The constuctor method is where the connection is made between the event fired by PrintForm and the fulfillment by the CustomForm.
public partial class MainForm : Form
{
public MainForm()
{
InitializeComponent();
// THIS IS THE "GLUE"
_printForm.ArrayRequest += _customForm.ArraysRequested;
}
private CustomForm _customForm = new CustomForm();
private PrintForm _printForm = new PrintForm();
// In MainForm.Designer.cs
protected override void Dispose(bool disposing)
{
if (disposing)
{
if (components != null)
{
components.Dispose();
}
_customForm.Dispose();
_printForm.Dispose();
}
base.Dispose(disposing);
}
private void buttonShowCustom_Click(object sender, EventArgs e)
{
_customForm.ShowDialog(owner: this);
}
private void buttonShowPrint_Click(object sender, EventArgs e)
{
_printForm.ShowDialog(owner: this);
}
}
You will need to adapt this to your specific requirements but hopefully this will give you some basics to go on.
I'm trying to send multiple values to a second form and display the text in a textbox without loosing the old values (every value in a new line), but i dont know how... Would be happy if somebody could help me :)
I searched everywhere to find a solution but couldn't find enything.
Code from data.cs
private static string Acc;
public static string GetAcc()
{
return Acc;
}
public static void SetAcc(string value)
{
Acc = value;
}
Code from Form 1
private void bunifuThinButton21_Click(object sender, EventArgs e)
{
Data.SetAcc(textBox1.Text);
}
Code from Form 2
public Generated()
{
InitializeComponent();
textBox1.Text = Data.GetAcc();
}
Now if I send a second value it should be displayed in the textbox in the next line and the first value should be in the first line.
Well, the general approach would be to use properties on the second form and set them in the calling form.
You seem to be using some kind of data holder that keeps all the data entered by the user. This is also a valid approach, but the way you
implement it doesn't fit what you describe.
If you want to keep several values you either need to use several properties or (in your case) a list of entries. Maybe this could be a better approach in your case:
Code from data.cs
private static List<string> Acc = new List<string>();
public static string[] GetAccounts()
{
return Acc.ToArray();
}
public static void AddAccount(string value)
{
Acc.Add(value)
}
Code from Form 1
private void bunifuThinButton21_Click(object sender, EventArgs e)
{
Data.AddAccount(textBox1.Text);
}
Code from Form 2
public Generated()
{
InitializeComponent();
textBox1.Text = String.Join(Environment.NewLine, Data.GetAccounts());
}
Ok, so I have a question regarding the EventArgs that can be passed when an event is triggered. I am designing a small, basic search engine and have a class called Query that contains a method Search. When this method is called, I want to trigger an event which will pass the results to be storred in a variety of cache class instances (SizeBoundedCache and TimeBoundedCache). So I thought the best way to do this would be to use an event.
The delegate is declared like this ->
public delegate void CacheStoreDelegate(object sender, EventArgs e);
The rest of the code within the Query class relevant to this question is here (uses Linq) ->
public event CacheStoreDelegate AddToCache;
public virtual void OnQuery (EventArgs e)
{
if(AddToCache != null)
AddToCache(this, e);
}
public Query()
{
}
public Query(string queryString, OOP5.Provided.QueryOperator op)
{
//Access and set the terms array
this.Terms = OOP5.Provided.QueryUtils.GetTermsFromString(queryString);
this.Operator = op;
}
public static IEnumerable<string> Search (this SearchCore s, IQuery q)
{
// Accept a query and return IEnumerable<string> of
// all document IDs matching that query
if (q.Operator == QueryOperator.Any)
{
var GetAnyMatch = from single_query in q.Terms
group s.Search(single_query)
by s.documents.Keys
into results
where results.Count >= 1
select results[0];
this.OnQuery(GetAnyMatch);
return GetAnyMatch;
}
if (q.Operator == QueryOperator.All)
{
var GetAllMatch = from single_query in q.Terms
group s.Search(single_query)
by s.documents.Keys
into results
where results.Count >= q.Terms.Lengthselect results[0];
this.OnQuery(GetAllMatch);
return GetAllMatch;
}
}
All the cache classes will be notified whenever a search is called and I also need thme to receive the results.
Thanks so much in advance for the help. Also, if there is a more elegant way to do this that I am not thinking of, please chime in. Cheers!
You could create your own EventArgs implementation:
class QueryResultEventArgs : EventArgs
{
public IEnumerable<string> Results { get; private set; }
public QueryResultEventArgs(IEnumerable<string> results)
{
Results = results;
}
}
...
public delegate void CacheStoreDelegate(object sender, QueryResultEventArgs e);
...
this.OnQuery(new QueryResultEventArgs(GetAnyMatch));
Make a class of type CacheStoreEventArgs deriving from eventargs
public class CacheStoreEventArgs:eventargs
{
private IEnumerable<string> Data;//List<string> better
public IEnumerable<string> data
{
get { return Data; }
set { this.Data = value; }
}
public CacheStoreEventArgs(IEnumerable<string> NewData)
{
this.data = NewData;
}
}
then declare the event(use predefined generic one,so no need to declare one)
public event EventHandler<CacheStoreEventArgs> AddToCache;
inside your method search you call your method "On...."
public static IEnumerable<string> Search (this SearchCore s, IQuery q)
{
//after you get query result
CacheStoreEventArgs cs = new CacheStoreEventArgs(queryresultvariablehere);
//and call your method now with the instance of your derived eventargs class
OnQuery(cs);
}
public virtual void OnQuery (CacheStoreEventArgs e)
{
try
{
EventHandler<CacheStoreEventArgs> temp = AddToCache
if( temp != null)
temp(this,e);
}
catch(Exception ex)
{
//exception handling
}
}
I have a class Lot with a function AddPiece(piece).
I also have a Page with a button btnPanel that on click fires the function
public void btnPanel_OnClick(object sender, EventArgs e){}
I want to call the btnPanel_OnClick from the Addpiece function but when I try to do it it does not show in the intlliSense and I get this compilation error "The name 'btnPanel_OnClick' does not exist in the current context". Both classes are in the same namespace. Is this possible?
Here is what I have:
namespace GraphicW_Array
{
public partial class Board : System.Web.UI.Page
{
public void btnPanel_OnClick(object sender, EventArgs e)
{
...code...
}
}
}
and
namespace GraphicW_Array
{
public class Lot
{
public void addPiece(int piece)
{
lotPresent[lotLoad] = piece;
lotLoad++;
}
}
}
I think the answer is yes you can but you probably don't want to. To call the method you need and instance of your page class so you could do
namespace GraphicW_Array
{
public class Lot
{
public void addPiece(int piece)
{
lotPresent[lotLoad] = piece;
lotLoad++;
var myPage = new Board();
myPage.btnPanel_OnClick(null,EventArgs.Empty);
}
}
}
But what would that actually do? I have no idea because you haven't posted the code but i suspect it won't do anything useful for you.
What are you actually trying to achieve?
Maybe this is want you want
namespace GraphicW_Array
{
public class Lot
{
public void addPiece(int piece, Board myPAge)
{
lotPresent[lotLoad] = piece;
lotLoad++;
myPage.btnPanel_OnClick(null,EventArgs.Empty);
}
}
}
Then in your page you can call it like this:
var myLot = new Lot();
myLot.addPiece(4,this);
Yes, this is possible.
Ensure your Lot class has a reference to the Board class in order to be able to call it, or define an event on it that the Board class can subscribe to and that will call this mathod when the event fires.
If you don't use the sender and e parameters, just pass a null and EventArgs.Empty.
You can call page's event by passing either null(if sender and EventArgs is not mandatory) but below is the better way to go.
It is not wise and not good practice to call a event from a class, however you can create another method with arguments in your class and then call it with desired parameters when it is needed.
This is can be accomplished as below:
Say you have below event
public void btnPanel_OnClick(object sender, EventArgs e)
{
//Do some common tasks to do here
}
Rearrange it as below:
public void btnPanel_OnClick(object sender, EventArgs e)
{
Lot lot = new Lot();
lot.CommonFunction(arg1, arg2); // Pass required data
}
public class Lot
{
public void AFunction()
{
//Do something
//...
CommonFunction(arg1, arg2); // Pass required data
//...
//Do something
}
public void CommonFunction(string arg1, string arg2)
{
// Do some common tasks to do here
}
}
In one of my previous questions I explained about a form class that contain form field objects to save data in a user profile object (using profile provider).
The code is here bellow. Basically what I would like to accomplish is to pass as a parameter to my form field objects the field of the Profile object that they should interact in order to save the data later on.
You can see that in the following line:
//LastNameFormLine is an control that was added to my form page.
//The ProfileField parameter stores the field of the UserProfile object that is being manipulated by this control
LastNameFormLine.ProfileField = "UserProfile.LastName";
I was reading about reflection to be able to save this value in the UserProfileVisitor class, but I came across this concept of delegate in C# which I am not sure yet if I fully grasp.
Is it possible to delegate the ProfileField to a property on my UserProfile class? Or should I forget about it and go with reflection?
What would you suggest?
public partial class UserProfileForm : CustomIntranetWebappUserControl
{
protected override void OnInit(EventArgs e)
{
//AutoEventWireup is set to false
Load += Page_Load;
CancelLinkButton.Click += CancelButtonClickEvent;
SaveLinkButton.Click += SaveButtonClickEvent;
base.OnInit(e);
}
private void SaveButtonClickEvent(object sender, EventArgs e)
{
VisitFormFields();
}
private void VisitFormFields()
{
var userProfileVisitor = new UserProfileVisitor();
foreach (var control in Controls)
{
if (control is FormFieldUserControl)
{
var formField = (FormFieldUserControl) control;
formField.Visit(userProfileVisitor);
}
}
userProfileVisitor.Save();
}
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
BindText();
}
}
private void BindText()
{
LastNameFormLine.LabelText = string.Format("{0}:", HomePage.Localize("Last Name"));
LastNameFormLine.InputValue = UserProfile.LastName;
LastNameFormLine.IsMandatoryField = true;
LastNameFormLine.IsMultilineField = false;
LastNameFormLine.ProfileField = "UserProfile.LastName";
//... the rest of this method is exactly like the 4 lines above.
}
}
public abstract class FormFieldUserControl : CustomIntranetWebappUserControl
{
public string ProfileField { get; set; }
public abstract void Visit(UserProfileVisitor userProfileVisitor);
}
public partial class FormLineTextBox : FormFieldUserControl
{
//... irrelevant code removed...
public override void Visit(UserProfileVisitor userProfileVisitor)
{
if (userProfileVisitor == null)
{
Log.Error("UserProfileVisitor not defined for the field: " + ProfileField);
return;
}
userProfileVisitor.Visit(this);
}
}
public class UserProfileVisitor
{
public void Visit(FormLineTextBox formLine)
{
// The value of formLine.ProfileField is null!!!
Log.Debug(string.Format("Saving form field type {1} with profile field [{0}] and value {2}", formLine.ProfileField, formLine.GetType().Name, formLine.InputValue));
}
// ... removing irrelevant code...
public void Save()
{
Log.Debug("Triggering the save operation...");
}
}
Delegates are not for properties. However, Reflection is slow, may have issues with code security and it's not typesafe and may lead to runtime instead of compile-time problems on naming errors due to the late-bound nature.
That said, you may want to use getter and/or setter methods and use delegates on those.