Help with error in try catch statements

[shep0902]

I am working on a school project and I need to insert a try catch statement. When I insert the code below
Try
firstTextBox.Text

Catch ex As Exception

MsgBox("Please enter a numeric value in the first box.")
firstTextBox.Clear()

End Try

I get the error that says "Property access must assign to the property or use its value." Can anyone tell me what this error message means and how to correct it? I have attached my full code below in case that helps.

Thank you for your help in advance!

Public Class MainForm

Private Sub pythRadioButton_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles pythRadioButton.CheckedChanged

'Change Labels to Pythagorean Labels
firstLabel.Text = "A="
secondLabel.Text = "B="
thirdLabel.Text = "C="
End Sub

Private Sub cylRadioButton_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cylRadioButton.CheckedChanged

'Change Labels to Cylinder Labels
firstLabel.Text = "R="
secondLabel.Text = "H="
thirdLabel.Text = "V="
End Sub

Private Sub calcButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles calcButton.Click

Try
firstTextBox.Text

Catch ex As Exception
MsgBox("Please enter a numeric value in the first box.")
firstTextBox.Clear()
End Try


Try
secondTextBox.Text

Catch ex As Exception
MsgBox("Please enter a numeric value in the second box.")
secondTextBox.Clear()
End Try

If pythRadioButton.Checked Then 'If Pythagorean is checked

'Declare Variables
Dim a As Decimal
Dim b As Decimal
Dim c As Decimal

'Get the values
Decimal.TryParse(firstTextBox.Text, a)
Decimal.TryParse(secondTextBox.Text, b)

'Do the math
c = a ^ 2 + b ^ 2

'Output Answer
answerLabel.Text = Math.Sqrt(c)

Else 'If Pythagorean isn't checked, then Cylinder is

'Declare variables
Dim h As Decimal
Dim r As Decimal
Dim v As Decimal

'Get Values
Decimal.TryParse(firstTextBox.Text, h)
Decimal.TryParse(secondTextBox.Text, r)

'Do Cylinder Calculations'
v = (r ^ 2) * 3.14159 * h

'Output Answer
answerLabel.Text = v
End If

firstTextBox.Focus()
End Sub

Private Sub exitButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles exitButton.Click

Me.Close()
End Sub

Private Sub firstTextBox_Enter(ByVal sender As Object, ByVal e As System.EventArgs) Handles firstTextBox.Enter
firstTextBox.SelectAll()
End Sub

Private Sub firstTextBox_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles secondTextBox.TextChanged, firstTextBox.TextChanged
answerLabel.Text = ""
End Sub

Private Sub MainForm_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
pythRadioButton.Checked = True
End Sub


Private Sub clearButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles clearButton.Click
firstTextBox.Clear()
secondTextBox.Clear()

End Sub
End Class

[.paul.]

it means you're using it wrong:

firstTextBox.Text = "something"

or:

dim something as string = firstTextBox.Text

to check for a number using try, catch:

Try
dim decNumber as decimal = cdec(firstTextBox.Text)
 
Catch ex As Exception
MsgBox("Please enter a numeric value in the first box.")
firstTextBox.Clear()
End Try

if its successful, the number will be stored in decNumber, otherwise it'll display the msgbox