您如何使用数字和字母尝试tryCatch

Question

我应该添加一个TRY-CATCH，以确保用户输入的是数字值而不是字母值。当您输入字母并显示“有错误，请输入数字”时，它工作正常，但程序停止并显示错误：

这是我的代码

将intPoints设置为整数

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    txtPoints.Clear()
End Sub

Private Sub ExitToolStripMenuItem_Click(sender As Object, e As EventArgs) Handles ExitToolStripMenuItem.Click
    End
End Sub
Private Sub btnReward_Click(sender As Object, e As EventArgs) Handles btnReward.Click

    Try
        intPoints = txtPoints.Text

        intPoints = Convert.ToInt32(txtPoints.Text)

    Catch ex As Exception
    Finally
        MessageBox.Show("There was an error, please enter digits")

    End Try

    'intPoints = Convert.ToInt32(txtPoints.Text)



    If txtPoints.Text <= 0 Then
        MessageBox.Show("You cannot have less than 0")
    End If
    If txtPoints.Text = 1 Then
        MessageBox.Show("Keep Trying")
    End If
    If txtPoints.Text = 2 Then
        MessageBox.Show("Keep Trying")
    End If
    If txtPoints.Text = 3 Then
        MessageBox.Show("Keep Trying")
    End If
    If txtPoints.Text = 4 Then
        MessageBox.Show("Keep Trying")
    End If

    If txtPoints.Text = 5 Then
        MessageBox.Show("You're Gettomg close, just a few more!")
    End If
    If txtPoints.Text = 6 Then
        MessageBox.Show("You're Gettomg close, just a few more!")
    End If
    If txtPoints.Text = 7 Then
        MessageBox.Show("You're Gettomg close, just a few more!")
    End If
    If txtPoints.Text = 8 Then
        MessageBox.Show("You're Gettomg close, just a few more!")
    End If
    If txtPoints.Text = 9 Then
        MessageBox.Show("Almost, just one more!")
    End If
    If txtPoints.Text = 10 Then
        MessageBox.Show("Awesome! You earned a reward!")
    End If
    If txtPoints.Text >= 11 Then
        MessageBox.Show("You cannot have more than 10 points")
    End If


End Sub
' A computer uses 

结束班级