This is c#

add validation code and/or exception handling to EACH button

Validate that the user actually does enter something on each of the two text boxes

Validate that Modulus operation is not being done with negative numbers.

If either number is negative in the modulus operation, then a validation check fails and an error message needs to be displayed

Handle any exception created during the conversion of the textbox contents to a number

Handle any exception created by dividing by zero OR prevent it by validation

Handle any "unexpected" exceptions in the entire application

This will require lots of Try/Catch combinations

Display all messages to the user about invalid numbers or exceptions in the label, do not use a MessageBox

Each error or validation check failure needs a message associated with it. Do not do the process where the user fixes one error to just get another because you did not display all the error messages at once

Existing code:

namespace Module6MethodsProjectDL { public partial class frmActors : Form { // Public Contsants to use const byte ADD = 0; const byte SUBTRACT = 1; const byte MULTIPLY = 2; const byte DIVIDE = 3; const byte MODULUS = 4;

public frmActors() { InitializeComponent(); }

private void btnModulo_Click(object sender, EventArgs e) { decimal dLeft = 0.0m; decimal dRight = 0.0m; decimal dAnswer = 0.0m; string szLeft = ""; string szRight = ""; string szAnswer = ""; string szEquation = "";

szLeft = txtLeftOperand.Text; szRight = txtRightOperand.Text;

dLeft = Convert.ToDecimal(szLeft); dRight = Convert.ToDecimal(szRight);

dAnswer = dLeft % dRight;

szAnswer = dAnswer.ToString();

szEquation = szLeft + " % " + szRight + " = " + szAnswer;

lblAnswer.Text = ""; lblAnswer.Text = szEquation;

}

private void btnDivide_Click(object sender, EventArgs e) { decimal dLeft = 0.0m; decimal dRight = 0.0m; decimal dAnswer = 0.0m; string szLeft = ""; string szRight = ""; string szAnswer = ""; string szEquation = "";

szLeft = txtLeftOperand.Text; szRight = txtRightOperand.Text;

dLeft = Convert.ToDecimal(szLeft); dRight = Convert.ToDecimal(szRight);

dAnswer = dLeft / dRight;

szAnswer = dAnswer.ToString();

szEquation = szLeft + " / " + szRight + " = " + szAnswer;

lblAnswer.Text = ""; lblAnswer.Text = szEquation;

}

private void btnMultiply_Click(object sender, EventArgs e) { decimal dLeft = 0.0m; decimal dRight = 0.0m; decimal dAnswer = 0.0m; string szLeft = ""; string szRight = ""; string szAnswer = ""; string szEquation = "";

szLeft = txtLeftOperand.Text; szRight = txtRightOperand.Text;

dLeft = Convert.ToDecimal(szLeft); dRight = Convert.ToDecimal(szRight);

dAnswer = dLeft * dRight;

szAnswer = dAnswer.ToString();

szEquation = szLeft + " * " + szRight + " = " + szAnswer;

lblAnswer.Text = ""; lblAnswer.Text = szEquation;

}

private void btnMinus_Click(object sender, EventArgs e) { decimal dLeft = 0.0m; decimal dRight = 0.0m; decimal dAnswer = 0.0m; string szLeft = ""; string szRight = ""; string szAnswer = ""; string szEquation = "";

szLeft = txtLeftOperand.Text; szRight = txtRightOperand.Text;

dLeft = Convert.ToDecimal(szLeft); dRight = Convert.ToDecimal(szRight);

dAnswer = dLeft - dRight;

szAnswer = dAnswer.ToString();

szEquation = szLeft + " - " + szRight + " = " + szAnswer;

lblAnswer.Text = ""; lblAnswer.Text = szEquation;

}

private void btnPlus_Click(object sender, EventArgs e) { decimal dLeft = 0.0m; decimal dRight = 0.0m; decimal dAnswer = 0.0m; string szLeft = ""; string szRight = ""; string szAnswer = ""; string szEquation = "";

szLeft = txtLeftOperand.Text; szRight = txtRightOperand.Text;

dLeft = Convert.ToDecimal(szLeft); dRight = Convert.ToDecimal(szRight);

dAnswer = dLeft + dRight;

szAnswer = dAnswer.ToString();

szEquation = szLeft + " + " + szRight + " = " + szAnswer;

lblAnswer.Text = ""; lblAnswer.Text = szEquation;

} } }