Write VB.NET code for a reset button and a data validation function for a product form.

Question

ScanSolve AI Tutor · Accepted Answer

Here are the VB.NET solutions and explanations for the questions.

QUESTION 2

a) VB.NET sub procedure for the Reset Button:

This procedure clears the content of all TextBoxes and resets the ComboBox selection.

Private Sub btnReset_Click(sender As Object, e As EventArgs) Handles btnReset.Click
    ' Clear the ComboBox selection
    productIDComboBox.SelectedIndex = -1

    ' Clear the TextBoxes
    productNameTextBox.Text = ""
    qualityTextBox.Text = "" ' Assuming 'qualityTextBox' is for Quantity
    priceTextBox.Text = ""
    amountToPayTextBox.Text = ""

    ' Optionally, set focus to the first input control
    productIDComboBox.Focus()
End Sub

b) validateData() function:

This function checks if all controls have data, if Quantity and Price are numeric, and if a Product ID is selected.

Function validateData() As Boolean
    ' Check if Product ID is selected in the ComboBox
    If productIDComboBox.SelectedIndex = -1 Then
        MessageBox.Show("Please select a Product ID.", "Validation Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
        productIDComboBox.Focus()
        Return False
    End If

    ' Check if Product Name is empty
    If String.IsNullOrEmpty(productNameTextBox.Text) Then
        MessageBox.Show("Product Name cannot be empty.", "Validation Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
        productNameTextBox.Focus()
        Return False
    End If

    ' Check if Quantity is empty
    If String.IsNullOrEmpty(qualityTextBox.Text) Then ' Assuming 'qualityTextBox' is for Quantity
        MessageBox.Show("Quantity cannot be empty.", "Validation Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
        qualityTextBox.Focus()
        Return False
    End If

    ' Check if Price is empty
    If String.IsNullOrEmpty(priceTextBox.Text) Then
        MessageBox.Show("Price cannot be empty.", "Validation Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
        priceTextBox.Focus()
        Return False
    End If

    ' Check if Amount to Pay is empty (if it's an input field, otherwise it's calculated)
    ' Assuming it needs to be checked as per "All controls... must not be empty"
    If String.IsNullOrEmpty(amountToPayTextBox.Text) Then
        MessageBox.Show("Amount to Pay cannot be empty.", "Validation Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
        amountToPayTextBox.Focus()
        Return False
    End If

    ' Check if Quantity is numeric
    Dim quantity As Decimal
    If Not Decimal.TryParse(qualityTextBox.Text, quantity) Then
        MessageBox.Show("Quantity must be a numeric value.", "Validation Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
        qualityTextBox.Focus()
        Return False
    End If

    ' Check if Price is numeric
    Dim price As Decimal
    If Not Decimal.TryParse(priceTextBox.Text, price) Then
        MessageBox.Show("Price must be a numeric value.", "Validation Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
        priceTextBox.Focus()
        Return False
    End If

    ' All validation checks passed
    Return True
End Function

QUESTION 3

a) Two business rules for data validation:

Quantity must be positive: The quantity of an item purchased cannot be zero or a negative number.
Price must be positive: The price of an item cannot be zero or a negative number.

b) How variables are created in VB.NET:

In VB.NET, variables are created using the Dim keyword, followed by the variable name, the As keyword, and then the data type. Optionally, an initial value can be assigned using the assignment operator =. This process declares the variable, reserving memory for it and specifying the type of data it can hold.

Example:

Dim customerName As String = "John Doe"
Dim productPrice As Decimal

c) Explain the term syntax error with an example:

A syntax error occurs when a programmer writes code that violates the grammatical rules or structure of the programming language. These errors are typically detected by the compiler or integrated development environment (IDE) before the program can run, preventing compilation. They are like spelling or grammar mistakes in human language.

Example:
If you write Dim myVariable As Intager instead of Dim myVariable As Integer, the compiler will flag Intager as a syntax error because Intager is not a recognized data type in VB.NET.

Write VB.NET code for a reset button and a data validation function for a product form.

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