Demo Project: • Complex Calculator What will you learn? • Adding single event handlers for Multiple Buttons • Identifying from which button handler is called. • Using flag variable to write smart code.

1. Demo Project:
• Complex Calculator
What will you learn?
• Adding single event handlers
• Identifying from which button handler is called.
• Using flag variable to write smart
Windows Forms for Beginners
www.dotnetvideotutorial.com
single event handlers for Multiple Buttons
dentifying from which button handler is called.
Using flag variable to write smart code.
Bhushan Mulmule
bhushan.mulmule@gmail.com
www.dotnetvideotutorial.com
Windows Forms for Beginners
Part 4
Bhushan Mulmule
bhushan.mulmule@gmail.com
www.dotnetvideotutorial.com
Windows Forms for Beginners

2. www.dotnetvideotutorial.com
Demo Project 1: Complex Calculator
Step 1: Design UI:
Instructions:
• When clicked on any number button that number should get displayed on label
lblDisplay.
• As all numeric buttons have same functionality we will add single handler
Digit_Click for click event of all numeric buttons
Label:
Name: lblDisplay
AutoSize: False
BackColor: White
BorderStyle: FixedSingle
Text: Blank
TextAlign: MiddleRight
Form:
Name: frmCalculator
Text: Calculator
18 Buttons:
Text: 1, 2, 3, 4, 5, 6, 7, 8, 9, 0,
., C, +, -, *, /, =, OFF
Name: Name accordingly for
example btn1, btnPlus,
btnOFF, etc
2 Group Boxes:
Text: Blank

3. www.dotnetvideotutorial.com
• As all operator buttons have same functionality we will add single handler
Operator_Click for click event of all operator buttons
Step 2: Adding event handlers
1. Right click on form Click View code.
2. In class frmCalculator Declare following variables
public partial class frmCalculator : Form
{
double no1, no2, result;
string op;
bool flg;
…..
}
3. Insert single event handler for all numeric buttons.
• First Select number 1 button (btn1)
• Press Control key and then select all number buttons
• Go to property window Switch to event view by clicking light sign (see
image below: pointed by Event Button call out) Locate Click event
Type “Digits_Click” Press enter and handler will be inserted
Events Button
Click Event
All number
buttons are
selected

4. www.dotnetvideotutorial.com
4. In Digits_Click() handler write following code
private void Digits_Click(object sender, EventArgs e)
{
if (flg == true)
{
lblDisplay.Text = "";
flg = false;
}
Button btn = (Button)sender;
lblDisplay.Text += btn.Text;
}
5. Insert single event handler for all operator buttons
• Select Plus button then press control key and select Minus, Multiplication
and Division buttons.
• Do not select Equal (=) button
• Go to property window Events list Locate Click event and type
“Operator_Click()” and press enter. code it as follow
private void Operator_Click(object sender, EventArgs e)
{
no1 = Convert.ToInt32(lblDisplay.Text);
op = ((Button)sender).Text;
flg = true;
}
6. Double click on equal button and insert following code
private void btnEqual_Click(object sender, EventArgs e)
{
no2 = Convert.ToDouble(lblDisplay.Text);
switch (op)
{
case "+":
result = no1 + no2;
break;
case "-":
result = no1 - no2;
break;
case "*":
result = no1 * no2;
break;
case "/":

5. www.dotnetvideotutorial.com
result = no1 / no2;
break;
}
lblDisplay.Text = result.ToString();
flg = true;
}
7. Double click on point button
private void btnPoint_Click(object sender, EventArgs e)
{
if(! lblDisplay.Text.Contains("."))
lblDisplay.Text += ".";
}
8. Clear button
private void btnClear_Click(object sender, EventArgs e)
{
no1 = 0;
no2 = 0;
result = 0;
lblDisplay.Text = "";
}
9. OFF button
private void btnOFF_Click(object sender, EventArgs e)
{
Application.Exit();
}
10.Execute and test.
11.Debug step by step using F11 to understand logic