Windows Forms: How to make a Calculator in C#

Dragging the TextBox, Button from the visual studio toolbox to your winform, then design a simple calculator as shown below.

Next, Add code to handle your calculator form as the following c# code.

double value;
string coperator;
bool check;

Create the PNumber method allows you to display the numeric value that you enter in the TextBox control.

//Handle number button
private void PNumber(object sender, EventArgs e)
{
    if ((coperator == "+") || (coperator == "-") || (coperator == "*") || (coperator == "/"))
    {
        if (check)
        {
            check = false;
            txtResult.Text = "0";
        }
    }
    Button b = sender as Button;
    if (txtResult.Text == "0")
        txtResult.Text = b.Text;
    else
        txtResult.Text += b.Text;
}

Create the POperator method allows you to convert text to numeric.

//Handle operator button
private void POperator(object sender, EventArgs e)
{
    Button b = sender as Button;
    //Convert text to number
    value = double.Parse(txtResult.Text);
    coperator = b.Text;
    txtResult.Text += b.Text;
    check = true;
}

Add the button click event handler to the Equal button allows you to calculate the result value.

private void button20_Click(object sender, EventArgs e)
{
    try
    {
        switch (coperator)
        {
            case "+":
                txtResult.Text = (value + double.Parse(txtResult.Text)).ToString();
                break;
            case "-":
                txtResult.Text = (value - double.Parse(txtResult.Text)).ToString();
                break;
            case "*":
                txtResult.Text = (value * double.Parse(txtResult.Text)).ToString();
                break;
            case "/":
                txtResult.Text = (value / double.Parse(txtResult.Text)).ToString();
                break;
        }
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.Message, "Message", MessageBoxButtons.OK, MessageBoxIcon.Error);
    }
}

Add the button click event handler to the C button allows you to reset the result value to zero.

private void button5_Click(object sender, EventArgs e)
{
    txtResult.Text = "0";
}

Add the button click event handler to the CE button allows you to clear memory and reset the result value to zero.

//Clear memory
private void button10_Click(object sender, EventArgs e)
{
    txtResult.Text = "0";
    value = 0;
}

This is only a simple calculator that helps you perform some calculations. The application built is designed to emulate the windows calculator and is done in c# .net

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