Develop Reference

Assigning unique values to the index of an array

I am trying to make my button take input from a textbox and add it to the index. The problem is that with everything I have tried, I cannot get it to give a unique value to each position in the index.
private void addBtn_Click(object sender, EventArgs e)
{
for (int i = 0; i < nums.Length; i++)
{
if (nums[0] == 0)
{
nums[0] = int.Parse(inputText.Text);
i++;
}
if (nums[1] == 0)
{
nums[1] = int.Parse(inputText.Text);
i++;
}
}
MessageBox.Show(nums[i].ToString());
}
Right now my code inserts the value to both index positions instead of assigning a value to position 0 and then allowing the user to insert a different value into position 1 and so on and so on.

It's not clear what your intent is, but it looks like you might be trying to add numbers to an array. This code will assign the parsed string to the first item in the array that isn't zero.
private void addBtn_Click(object sender, EventArgs e)
{
int i = 0;
for (; i < nums.Length; i++)
{
if (nums[i] == 0)
{
nums[i] = int.Parse(inputText.Text);
break;
}
}
MessageBox.Show(nums[i].ToString());
}
But this would be a better way, because the user might type "0":
private int _lastUsedIndex = -1;
private void addBtn_Click(object sender, EventArgs e)
{
var number = int.Parse(inputText.Text);
// Increment by one
++_lastUsedIndex;
nums[_lastUsedIndex] = number;
MessageBox.Show(number.ToString());
}
But still, arrays aren't a great idea: They can't grow as you add things. First they're bigger than you need, then suddenly they're too small and you crash. We have better options now. Unless your teacher insists that you must use an array, use List<int> instead. In this version, we'll also use a different way to parse the number, which won't crash if the user types "LOLWUT?!?!" instead of a number:
private List<int> nums = new List<int>();
private void addBtn_Click(object sender, EventArgs e)
{
int number;
if (int.TryParse(inputText.Text, out number))
{
nums.Add(number);
MessageBox.Show(number.ToString());
}
else
{
MessageBox.Show(inputText.Text + " isn't a number, smart guy.");
}
}

Looking to call method with parameter to take in specified text box

I am creating a Windows Form Application and I want to create a method to be able to pass in a specified text box from a _Click event. Such as below: My Method is AddTo() and I want to call from the 2 click events which have 2 separate text boxes. I want to be able to pass in the correct text box.
void AddTo(string ctrl)
{
int num= int.Parse(ctrl);
num++;
ctrl = num.ToString();
}
private void btnAddLevel_Click(object sender, EventArgs e)
{
AddTo(TextBox1.Text);
}
private void btnAddSecond_Click(object sender, EventArgs e)
{
AddTo(TextBox2.Text);
}
I am pretty new to C#, is this possible to do? Thanks in advance for any help.
UPDATE:
Here is the full code with the fix below
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
txtName.Text = "0";
}
void AddTo(ref TextBox tBox)
{
if (tBox.Text.Trim().Length > 0)
{
int num = 0;
//CHECK IF THE TEXT IS CONVERTIBLE TO NUMBER
if (int.TryParse(tBox.Text, out num))
{
num++;
tBox.Text = num.ToString();
}
}
}
private void btnAddUnit_Click(object sender, EventArgs e)
{
AddTo(ref txtName);
}
}

Use ref key word to retain data updates for passing objects.
Try below code:
//YOUR TEXTBOX IS A REFERNCE HERE. SO THAT THE UPDATES ARE RETAINED
void AddTo(ref TextBox tBox)
{
//VALIDATED YOUR TEXT BOX IF DATA EXISTS BEFORE UPDATING
if (tBox.Text.Trim().Length > 0 )
{
int num = 0;
//CHECK IF THE TEXT IS CONVERTIBLE TO NUMBER
if (int.TryParse(tBox.Text, out num))
{
num++;
tBox.Text = num.ToString();
}
}
}
While calling
//USE REF WHILE CALLING
AddTo(ref textBox1);//textbox object

Fill a textbox based on another textbox text

I have TextBoxA and TextBoxB. What i want to do is , whenever i put a number (yes, both of the textboxes values are always integers) in TextBoxA , TextBoxB should "autocomplete" with value (100-TextBoxA). Same thing goes for TextBoxB. The sum of TextBoxA and TextBoxB should always be 100.
Here's what i've already tried:
static void TextBoxA_TextChanged()...
{
int a = Convert.ToInt32(TextBoxA.Text);
int b = Convert.ToInt32(TextBoxB.Text);
string text = (100-a).ToString();
TextBoxB.Text = text;
}
Static void TextBoxB_TextChanged()...
{
int a = Convert.ToInt32(TextBoxA.Text);
int b = Convert.ToInt32(TextBoxB.Text);
string text = (100-b).ToString();
TextBoxA.Text = text;
}
But it doesn't work.

Here's what you can try:
private void TextBoxA_TextChanged(object sender, EventArgs e)
{
int num = 0;
if (int.TryParse(TextBoxA.Text, out num))
{
string text = (100 - num).ToString();
TextBoxB.Text = text;
}
}
private void TextBoxB_TextChanged(object sender, EventArgs e)
{
int num = 0;
if (int.TryParse(TextBoxB.Text, out num))
{
string text = (100 - num).ToString();
TextBoxA.Text = text;
}
}
This will autocomplete on either TextBox on TextChanged Event.

First, i dont know why your event handlers are declared static.. its usually got to be :
private void TextBoxA_TextChanged(object sender, EventArgs e) { }
Secondly, you know if you have 2 textboxs, and each one triggers the other, you'll never go out of the TextChanged event.
To understand me more, here's an example :
1- You set TextBoxB.text = "1";2- TextBoxB.TextChanged triggers, it
sets TextBoxA.Text = "2"; 3- TextBoxA.TextChanged triggers, it sets
TextBoxB.Text = "1";
And it continues like this until i believe you'll get an Exception of memory.
EDIT : The opertator '-' works on numbers. You can't substract a number from a string. they have to be both numbers, so convert them first.
EDIT 2 :
Here's a code i wrote that works fine
private void textBox1_TextChanged(object sender, EventArgs e)
{
int n;
if (int.TryParse(textBox1.Text, out n)) // Check if the text value is a number
{
if (n > 100) // Since you want a sum of 100
return;
int m = 100 - n; // remaining
if (textBox2.Text != m.ToString()) // to not re-trigger the TextChanged event
textBox2.Text = m.ToString();
}
}
private void textBox2_TextChanged(object sender, EventArgs e)
{
int n;
if (int.TryParse(textBox2.Text, out n)) // Check if the text value is a number
{
if (n > 100) // Since you want a sum of 100
return;
int m = 100 - n; // remaining
if (textBox1.Text != m.ToString()) // to not re-trigger the TextChanged event
textBox1.Text = m.ToString();
}
}

Try this. This is a more efficient and elegant way I'd choose using lambda expressions, without repeating the method:
private void onChangeDoSum(object sender, EventArgs e,
TextBox substractNumber, TextBox sumNumber)
{
sumNumber.Text = (100 - Int32.Parse(substractNumber.Text)).ToString();
}
private void Form1_Load(object sender, EventArgs e)
{
textBox1.TextChanged += (a, b) => onChangeDoSum(sender, e, textBox1, textBox2);
textBox2.TextChanged += (a, b) => onChangeDoSum(sender, e, textBox2, textBox1);
}
Alternatively use Int32.TryParse to prevent unexpected results.

I think you can do something like this
private void textBox1_TextChanged(object sender, EventArgs e)
{
textBox2.Text = (100 - Int32.Parse(textBox1.Text)).ToString();
}
private void textBox2_TextChanged(object sender, EventArgs e)
{
textBox1.Text = (100 - Int32.Parse(textBox2.Text)).ToString();
}
when I see that static word I think you have tried to create these method by yourself and you forgot to add
textBox1.TextChanged += textBox1_Changed;
// I saw other post where you wrote that it could raise exception and fall. Of course it can. You can use if condition like
textBox1.Text != null && textBox1.Text != ""
before value would be changed or TryParse() method

Validate number INTEGER on text boxes IN windows forms issue

i have textbox on a windows form and i want to be insert only numbers in this textbox.i use the following c# code for that
private void ChildAge_TextChanged(object sender, EventArgs e)
{
int i;
if (!int.TryParse(ChildAge.Text, out i))
{
MessageBox.Show("Plaese enter a valid Age");
}
}
it is working, but the problem is that , after showing the Message, when i Backspace the content and text box become null, on that situation also this message box shows again.

Do a little test like bellow:
int i = 0;
if(!string.IsNullOrEmpty(ChildAge.Text) &&
!int.TryParse(ChildAge.Text, out i)
)
{
MessageBox.Show("Enter Valid Age");
}

Try Using Below. This works better.
bool m_BackPressed = false;
private void ChildAge_TextChanged(object sender, EventArgs e)
{
int i;
if (!m_BackPressed)
{
if (!int.TryParse(ChildAge.Text, out i))
{
MessageBox.Show("Plaese enter a valid Age");
}
}
}
private void ChildAge_KeyPress(object sender, KeyPressEventArgs e)
{
m_BackPressed = (e.KeyChar.Equals((char)Keys.Back)) ? true : false;
}

How to prevent crashing from a invalid input in C#

I made a simple application to add 2 numbers together but when I add two letters together or a invalid sign it crashes the program. How do I create a message box showing something saying "please put in a number" when someone inserts a letter
Here's my code:
public partial class frmAdd : Form
{
string first;
string second;
public frmAdd()
{
InitializeComponent();
}
private void btnFirst_Click(object sender, EventArgs e)
{
first = txtNumber.Text;
}
private void btnSecond_Click(object sender, EventArgs e)
{
second = txtNumber.Text;
}
private void btnResult_Click(object sender, EventArgs e)
{
int a = Convert.ToInt32(first);
int b = Convert.ToInt32(second);
int c = a + b;
txtResult.Text = c.ToString();
}
}

Use TryParse instead:
private void btnResult_Click(object sender, EventArgs e)
{
int a, b;
if (int.TryParse(first, out a) && int.TryParse(second, out b))
{
int c = a + b;
txtResult.Text = c.ToString();
}
else
{
MessageBox.Show("Invalid Input!");
}
}
Or perhaps a better method would be to trap the error when the user first inputs the data:
public partial class frmAdd : Form
{
int first; // changed to int
int second;
private void btnFirst_Click(object sender, EventArgs e)
{
if (!int.TryParse(txtNumber.Text, out this.first))
{
MessageBox.Show("Invalid Input!");
}
}
private void btnSecond_Click(object sender, EventArgs e)
{
if (!int.TryParse(txtNumber.Text, out this.second))
{
MessageBox.Show("Invalid Input!");
}
}
private void btnResult_Click(object sender, EventArgs e)
{
int c = first + second;
txtResult.Text = c.ToString();
}
}

You can use NumericUpDown control instead of TextBox - it will not allow user to input invalid data.
Or you can add validation to TextBox value after user entered something. Add ErrorProvider to your form. And subscribe to Validating event of txtNumber textbox. This event will occur when textbox loses focus. If entered text is not an integer, then error will be shown near texbox, and your button will not be clicked:
private void txtNumber_Validating(object sender, CancelEventArgs e)
{
int value;
if (!Int32.TryParse(txtNumber.Text, out value))
{
errorProvider1.SetError(txtNumber, "Value is not an integer");
return;
}
errorProvider1.SetError(txtNumber, "");
first = value; // it's better to save integer value than text
}
Validation looks like:

You can add a bit of validation to check if you can create an int from the string value passed in.
int.TryParse is a simple way of doing this.
And for the MessageBox you can just use the MessageBox calss
Example:
private void btnResult_Click(object sender, EventArgs e)
{
int a = 0;
int b = 0;
if (!int.TryParse(first, out a))
{
MessageBox.Show("first is not a number");
return;
}
if (!int.TryParse(second, out b))
{
MessageBox.Show("second is not a number");
return;
}
int c = a + b;
txtResult.Text = c.ToString();
}

Instead of using Convert.ToInt32(string), you might actually use Int32.tryParse(String, out int), as shown below:
int a, b;
a = Int32.tryParse(first, out a);
b = Int32.tryParse(second, out b);
If the conversion fails, the tryParse method will result in a zero. If it succeeds, it will give you the number which is to be found in the string.
Hope it helped you out, had to find this too in my first few days of C#.