I know how to create programs in C++, but very new to C# so be patient, but I have a question, and for the life of my couldn't find it on google, or stackoverflow search (maybe didn't know a good way to phrase it). I have two functions on my form: A NumericUpDown, and a Button. When the button is clicked, I want to grab the data from NumericUpDown, and .Show() it in a message box. Here is what I currently have.
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void StatBox_ValueChanged(object sender, EventArgs e)
{
//decimal Stat = StatBox.Value;
//string StatStr = Stat.ToString();
}
private void button1_Click(object sender, EventArgs e)
{
MessageBox.Show(StatBox.Value);
}
}
Like C++, C# is a strongly-typed language. That means that you will get a compile-time error if you try to pass an int to a function that accepts a string, or vice versa. That's what is happening to you here.
The simplest overload of the MessageBox.Show function accepts a single string parameter, yet you've passed it a decimal (the result of StatBox.Value):
MessageBox.Show(StatBox.Value);
The fix is simple: convert the decimal to a string. All .NET objects provide a ToString member function that can be used to obtain a string representation of the object. So rewrite your code like so:
MessageBox.Show(StatBox.Value.ToString());
You can even get fancy and concatenate a number of sub-strings together when calling this function, just like you can with the C++ string type and I/O streams. For instance, you might write this code:
MessageBox.Show("The result is: " + StatBox.Value.ToString());
or use the String.Format method, which is somewhat similar to the C printf function. Then you can specify a standard or custom numeric format and avoid calling the ToString function explicitly. For example, the following code will display the number in the up-down control in fixed-point notation with exactly two decimal places:
MessageBox.Show(String.Format("The result is: {0:F2}", StatBox.Value.ToString()));
This should do it for you:
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void StatBox_ValueChanged(object sender, EventArgs e)
{
//decimal Stat = StatBox.Value;
//string StatStr = Stat.ToString();
}
private void button1_Click(object sender, EventArgs e)
{
MessageBox.Show(StatBox.Value.ToString());
}
}
Since you are using a MessageBox to .Show() the data, you will want to call the .ToString() method on the StatBox.Value.
PS - Welcome to SO! You will love it here.
Related
I am struggling to pass data between two forms (all I want to do is have a textbox in Form1, and show that textbox value in textbox1, which is located in Form2). How would I go about this, using WPF? Have looked at quite a few solutions, but cannot seem to get any of them at all to work.
For the form in which I'm wanting to display the values (in tbd.Text), here is the code:
namespace test
{
/// <summary>
/// Interaction logic for OptionDisplayWindow.xaml
/// </summary>
public partial class OptionDisplayWindow : Window
{
public OptionDisplayWindow()
{
InitializeComponent();
tbd.Text = "k"; //want to change this value based on "s" in the other form
}
The form in which the text is transferred from (want to display the string):
public void Button1_Click(object sender, RoutedEventArgs e)
{
string s = "testText"
}
I have tried every single other answer on SO (spent the past 6 hours trying) and have had absolutely no luck.
EDIT 2: Using the method listed as the best answer here Send values from one form to another form I've come up with this code for Form1:
private void ttbtn_Click(object sender, RoutedEventArgs e)
{
using (Form2 form2 = new Form2())
{
tbd.Text = form2.TheValue;
}
}
And the code for Form2:
public string TheValue
{
get { return arrayTest.Text; }
}
However, I'm getting the error 'Form 2': type used in a using statement must be implicitly convertible to 'System.IDisposable'.
The code that you put in the sample project (that you provided as a link in the comments) should be in your question. Given that it becomes much easier to understand what you're trying to do and to give you a workable solution.
I would suggest creating a "DataTransferObject" and pass that between each form.
public class Dto
{
public string Text;
}
The code in MainWindow would then look like this:
private void button1_Click(object sender, RoutedEventArgs e)
{
var dto = new Dto();
window2 win2 = new window2();
win2.Dto = dto;
win2.ShowDialog();
textBox1.Text = dto.Text;
}
And the code in window2 would look like this:
public Dto Dto;
private void textBox2_TextChanged(object sender, TextChangedEventArgs e)
{
if (this.Dto != null)
{
this.Dto.Text = textBox2.Text;
}
}
That is one way - out of about a million - of transferring data between forms. An advantage of using a data transfer object is that it begins you on the road of separating your data from your UI, and that is generally a very good thing to do.
Another simple way to pass data between forms is using your application's settings.
Step 1: Create a setting, open the "Project" menu and pick "test Properties..."
this will take you to the settings page, create a setting name it however you want, I named mine "PassString" and make sure it's a string type and the Scope is set to user.
Step 2. Lets set the string setting to your textbox.text property, add these changes to the code:
private void button1_Click(object sender, RoutedEventArgs e)
{
Properties.Settings.Default.PassString = textBox1.Text;
window2 win2 = new window2();
win2.ShowDialog();
}
Step 3. Update the text on your second window Initialization Process.
public OptionDisplayWindow()
{
InitializeComponent();
tbd.Text = Properties.Settings.Default.PassString;
}
P.S. you may have to add a reference to reach your application settings.
using test.Properties;
I am using Windows Form Application and am having an issue clearing a user textbox. The textbox is getting parsed as an int. I have a button near the bottom of the app that allows a user to clear different parts of the form, labels textboxes etc.
The labels clear fine but any textbox that has been parsed to int I get error on the TextChanged method.
xxx = textbox name
yyy = new int var used in other parts of code
when xxx.Clear(); is called I get exception below:
An unhandled exception of type
System.FormatException' occurred in mscorlib.dll
Additional information: Input string was not in a correct format.
Here is example of code
private void xxx_TextChanged(object sender, EventArgs e){
// parse user text and convert to int
yyy = int.Parse(xxx.Text);
}
private void btnExit_Click(object sender, EventArgs e){
// close program
this.Close();
}
private void btnClear_Click(object sender, EventArgs e){
xxx.Clear();
}
put the textBoxName.Text in a variable and check if its value is null or not.
int xxx = textbox.Text ;
if(xxx == ""){
//do something
}
well when you use int32.parse you should be carefull that your string be not null and all contain numbers like
"123456789"
if you think you string might be null ot contain not number characters you should use:
int32.TryParse(string String, out int iString);
and use it like this:
int i = 0; // default
string s = "somthing123somthing456blah";
int32.TryParse(s, out i);
result should be: 123456 as integer
EDIT:
if you dont what TextChanged fire:
mytextbox.TextChanged -= myTextBox_TextChanged;
make you change and:
mytextbox.TextChanged += myTextBox_TextChanged;
I suspect something to do with code re-entry. When xxxTxtBox.Clear() is called, the TextChanged method is called, meaning int.parse is called on an empty textbox (null or string.empty can't be parsed to an integer), throwing an exception.
A preferred way to fix that may be setting a flag upon re-entry, something like this.
The easy way is put your TextChanged() logic in a try/catch, meaning that upon re-entry, the int.parse() fails but your user doesn't see a problem.
You need evaluate if the textbox is empty:
enter private void xxx_TextChanged(object sender, EventArgs e)
{
// parse user text and convert to int if value is't Empty
yyy = String.IsNullOrEmpty(xxx.Text) ? 0 : int.Parse(xxx.Text);
}
And try this:
private void btnClear_Click(object sender, EventArgs e){
xxx.Text = String.Empty;
}
To clarify, as some others have pointed out, the problem you are experiencing is due to the fact that xxx_TextChanged() is being called when xxx.Clear() is called and the textbox content changes to an empty string. This causes int.Parse() to execute against an empty string, which produces said error.
To circumvent this problem, you should change the xxx_TextChanged() method to something similar to as follows:
private void xxx_TextChanged(object sender, EventArgs e)
{
// Parse user text and convert to integer, when able:
if ((string.IsNullOrEmpty(xxx.Text)) ||
(!int.TryParse(xxx.Text, out yyy)))
{
yyy = 0;
}
}
Notice the key difference is the "null or empty" check against the text box contents. There is no need to parse a null value or an empty string. Also, instead of using int.Parse(), we can use the int.TryParse() method so that invalid numeric input (e.g., "abc") does not produce an error, but instead is assigned some default value (in this case, 0).
The rest of the code can remain as-is.
Before I start, I'd like to say that I have looked for an answer for this over the internet for quite a while, and unable to come to a solution. I know how to solve this, but it doesn't want to work.
Here's what I know: Assuming that I have a label and another class, if I want to manipulate the label I need to create an instance of the form that has the label, call the method of the new class with the form, and then call the method from within the form class that changes the label. This is what I have.
This is from the form class
private void button1_Click(object sender, EventArgs e)
{
Question steve = new Question(1, 1, "nothing", new string[] {});
steve.Show(new Form1(), "I win");
}
public void ChangeLabel(string s)
{
this.lblTest.Text = s;
}
And this is the Question class
public void Show (Form1 f, string str)
{
f.ChangeLabel(str);
}
Syntax-wise this is correct, and when running the debugger lblTest.Text did equal "I win", but there were no visual changes on the form.
P.S. I am in high school and still learning C#, so if I made any mistakes in my explanation or the code, please point them out. Also, disregard the Question constructor, it's useless right now.
Thanks
No ! you don't need to create new instance of the form.
You must pass the current instance using this keyword:
private void button1_Click(object sender, EventArgs e)
{
Question steve = new Question(1, 1, "nothing", new string[] {});
steve.Show(this, "I win"); //change it
}
I am trying to make a text box (UPC_txtBox4) self populate to equal the same value of UPC_txtBox2. The two text boxes are on separate forms but I feel there should be a way to link the two.
If form1 is responsible for navigating to form2, then you can pass the value on the query string from form1 using a URL similar to the following:
protected void Page_Load(object sender, EventArgs e)
{
if (this.IsPostBack)
{
Response.Redirect(Request.ApplicationPath + "/Form2.aspx?upc=" + UPC_txtBox2.Text, false);
}
}
then in form2 code:
protected void Page_Load(object sender, EventArgs e)
{
if (!this.IsPostBack)
{
// Assuming this field is an asp.net textbox and not an HTML input
UPC_txtBox4.Text = Request.QueryString["upc"];
}
}
Alternatively, you could store the value in session state, assuming that you are using sessions.
CORRECTION: Seeing as you are using WebForms, not WinForms as I had assumed, the below is irrelevant. I'll leave it just incase it helps someone else.
You should just create a method on the form that needs to be updated, then pass a reference when of that form to the newly created form.
This won't work if either form is a dialog (as far as I know).
So:
Form that has the textbox that will be directly edited.
private Form formToUpdate;
public void OpenForm(Form _formToUpdate)
{
formToUpdate = _formToUpdate;
txtBlah.TextChanged += new EventHandler(OnTextChanged);
this.Show();
}
private void OnTextChanged(object sender, EventArgs e)
{
formToUpdate.UpdateText(txtBlah.Text);
}
Form that is to be dynamically updated:
delegate void StringParameterDelegate (string value);
public void UpdateText(string textToUpdate)
{
if (InvokeRequired)
{
BeginInvoke(new StringParameterDelegate(UpdateText), new object[]{textToUpdate});
return;
}
// Must be on the UI thread if we've got this far
txtblah2.Text = textToUpdate;
}
Note: this is untested (although it should work), and largely pseudo code, you'll need to tailor it to your solution obviously.
I'm fairly new to C# programming.
I am making a program for fun that adds two numbers together, than displays the sum in a message box. I have two numericUpDowns and a button on my form. When the button is pushed I want it to display a message box with the answer.
The problem is, I am unsure how to add the twp values from the numericUpDowns together.
So far, I have this in my button event handler:
private void button1_Click(object sender, EventArgs e)
{
MessageBox.Show(this.numericUpDown1.Value + this.numericUpDown2.Value);
}
But obviously, it does not work. It gives me 2 compiler errors:
1. The best overloaded method match for 'System.Windows.Forms.MessageBox.Show(string) has some invalid arguments
2. Argument '1': cannot convert decimal to 'string'
Thanks!
this.numericUpDown1.Value + this.numericUpDown2.Value is actually evaluating properly to a number, so you're actually very close. The problem is that the MessageBox.Show() function, needs a string as an argument, and you're giving it a number.
To convert the result to a string, add .ToString() to it. Like:
private void button1_Click(object sender, EventArgs e)
{
MessageBox.Show((this.numericUpDown1.Value + this.numericUpDown2.Value).ToString());
}
For reference, if you want to do more advanced formatting, you'd want to use String.Format() instead of ToString(). See this page for more info on how to use String.Format().
This works.
decimal total = this.numericUpDown1.Value + this.numericUpDown2.Value;
MessageBox.Show(total.ToString());
MessageBox.Show expects a string as a parameter (that's the first error message).
Try this:
private void button1_Click(object sender, EventArgs e)
{
MessageBox.Show((this.numericUpDown1.Value + this.numericUpDown2.Value).ToString());
}
It takes the values from the numericUpDown components and adds them to get an object of the type Decimal. This is then converted to a String, which MessageBox takes.
Now that's easy. NumericUpDown.Value has a type of Decimal. Messagebox.Show() expects a String. All you need to do is
MessageBox.Show((this.numericUpDown1.Value + this.numericUpDown2.Value).ToString());
to convert the result of the addition to a string.