GPA計算器文本框問題

Question

我已經設計了一個GPA計算器，它們分別是8個文本框輸入課程名稱，8個文本框每個課程的小時數值，最後8個文本框用於您在這些課程中的字母等級。我需要花費信用時間的8個文本框出現問題。如果我不覺得每個人都有一個號碼，它會給我錯誤「輸入字符串格式不正確」。我想將它編程到如果用戶只需要5個課程，他們可以將其他3個文本框留空，並且在他們沒有填入信用時間的文本框中輸入「0」，並且只需計算GPA輸入了5個班級。如果用戶輸入信用時間的所有8個文本框，它會正常工作，但是，如果上面提到的錯誤代碼出現，如果他們不填寫全部8個。

Public Class Form1 

Dim QualityPoints As Double 
Dim CourseName, hours As String 

Private Sub btnTotalHours_Click(sender As Object, e As EventArgs) Handles btnTotalHours.Click 
    Dim totalHours As String 
    Dim Credit1, Credit2, Credit3, Credit4, Credit5, Credit6, Credit7, Credit8 As Integer 
    Credit1 = Integer.Parse(txtBoxCredit1.Text) 
    Credit2 = Integer.Parse(txtBoxCredit2.Text) 
    Credit3 = Integer.Parse(txtBoxCredit3.Text) 
    Credit4 = Integer.Parse(txtBoxCredit4.Text) 
    Credit5 = Integer.Parse(txtBoxCredit5.Text) 
    Credit6 = Integer.Parse(txtBoxCredit6.Text) 
    Credit7 = Integer.Parse(txtBoxCredit7.Text) 
    Credit8 = Integer.Parse(txtBoxCredit8.Text) 

    totalHours = CStr(txtBoxTotalHours.Text) 
    txtBoxTotalHours.Text = (Credit1 + Credit2 + Credit3 + Credit4 + Credit5 + Credit6 + Credit7 + Credit8) 

End Sub 

Private Sub btnTotalQualityPoints_Click(sender As Object, e As EventArgs) Handles btnTotalQualityPoints.Click 

    Select Case txtBoxGrade1.Text 
     Case "A" 
      QualityPoints += (4 * txtBoxCredit1.Text) 
     Case "B" 
      QualityPoints += (3 * txtBoxCredit1.Text) 
     Case "C" 
      QualityPoints += (2 * txtBoxCredit1.Text) 
     Case "D" 
      QualityPoints += (1 * txtBoxCredit1.Text) 
     Case "F" 
      QualityPoints += (0 * txtBoxCredit1.Text) 
     Case " " 
      QualityPoints += (0 * txtBoxCredit1.Text) 

    End Select 

    Select Case txtBoxGrade2.Text 
     Case "A" 
      QualityPoints += (4 * txtBoxCredit2.Text) 
     Case "B" 
      QualityPoints += (3 * txtBoxCredit2.Text) 
     Case "C" 
      QualityPoints += (2 * txtBoxCredit2.Text) 
     Case "D" 
      QualityPoints += (1 * txtBoxCredit2.Text) 
     Case "F" 
      QualityPoints += (0 * txtBoxCredit2.Text) 
     Case " " 
      QualityPoints += (0 * txtBoxCredit2.Text) 

    End Select 

    Select Case txtBoxGrade3.Text 
     Case "A" 
      QualityPoints += (4 * txtBoxCredit3.Text) 
     Case "B" 
      QualityPoints += (3 * txtBoxCredit3.Text) 
     Case "C" 
      QualityPoints += (2 * txtBoxCredit3.Text) 
     Case "D" 
      QualityPoints += (1 * txtBoxCredit3.Text) 
     Case "F" 
      QualityPoints += (0 * txtBoxCredit3.Text) 
     Case " " 
      QualityPoints += (0 * txtBoxCredit3.Text) 

    End Select 

    Select Case txtBoxGrade4.Text 
     Case "A" 
      QualityPoints += (4 * txtBoxCredit4.Text) 
     Case "B" 
      QualityPoints += (3 * txtBoxCredit4.Text) 
     Case "C" 
      QualityPoints += (2 * txtBoxCredit4.Text) 
     Case "D" 
      QualityPoints += (1 * txtBoxCredit4.Text) 
     Case "F" 
      QualityPoints += (0 * txtBoxCredit4.Text) 
     Case " " 
      QualityPoints += (0 * txtBoxCredit4.Text) 

    End Select 

    Select Case txtBoxGrade5.Text 
     Case "A" 
      QualityPoints += (4 * txtBoxCredit5.Text) 
     Case "B" 
      QualityPoints += (3 * txtBoxCredit5.Text) 
     Case "C" 
      QualityPoints += (2 * txtBoxCredit5.Text) 
     Case "D" 
      QualityPoints += (1 * txtBoxCredit5.Text) 
     Case "F" 
      QualityPoints += (0 * txtBoxCredit5.Text) 
     Case " " 
      QualityPoints += (0 * txtBoxCredit5.Text) 

    End Select 

    Select Case txtBoxGrade6.Text 
     Case "A" 
      QualityPoints += (4 * txtBoxCredit6.Text) 
     Case "B" 
      QualityPoints += (3 * txtBoxCredit6.Text) 
     Case "C" 
      QualityPoints += (2 * txtBoxCredit6.Text) 
     Case "D" 
      QualityPoints += (1 * txtBoxCredit6.Text) 
     Case "F" 
      QualityPoints += (0 * txtBoxCredit6.Text) 
     Case " " 
      QualityPoints += (0 * txtBoxCredit6.Text) 

    End Select 

    Select Case txtBoxGrade7.Text 
     Case "A" 
      QualityPoints += (4 * txtBoxCredit7.Text) 
     Case "B" 
      QualityPoints += (3 * txtBoxCredit7.Text) 
     Case "C" 
      QualityPoints += (2 * txtBoxCredit7.Text) 
     Case "D" 
      QualityPoints += (1 * txtBoxCredit7.Text) 
     Case "F" 
      QualityPoints += (0 * txtBoxCredit7.Text) 
     Case " " 
      QualityPoints += (0 * txtBoxCredit7.Text) 

    End Select 

    Select Case txtBoxGrade8.Text 
     Case "A" 
      QualityPoints += (4 * txtBoxCredit8.Text) 
     Case "B" 
      QualityPoints += (3 * txtBoxCredit8.Text) 
     Case "C" 
      QualityPoints += (2 * txtBoxCredit8.Text) 
     Case "D" 
      QualityPoints += (1 * txtBoxCredit8.Text) 
     Case "F" 
      QualityPoints += (0 * txtBoxCredit8.Text) 
     Case " " 
      QualityPoints += (0 * txtBoxCredit8.Text) 

    End Select 

    txtBoxTotalQualityPoints.Text = QualityPoints 

End Sub 

Private Sub btnClear_Click(sender As Object, e As EventArgs) Handles btnClear.Click 
    txtBoxCourse1.Clear() 
    txtBoxCourse2.Clear() 
    txtBoxCourse3.Clear() 
    txtBoxCourse4.Clear() 
    txtBoxCourse5.Clear() 
    txtBoxCourse6.Clear() 
    txtBoxCourse7.Clear() 
    txtBoxCourse8.Clear() 

    txtBoxCredit1.Clear() 
    txtBoxCredit2.Clear() 
    txtBoxCredit3.Clear() 
    txtBoxCredit4.Clear() 
    txtBoxCredit5.Clear() 
    txtBoxCredit6.Clear() 
    txtBoxCredit7.Clear() 
    txtBoxCredit8.Clear() 

    txtBoxGrade1.Clear() 
    txtBoxGrade2.Clear() 
    txtBoxGrade3.Clear() 
    txtBoxGrade4.Clear() 
    txtBoxGrade5.Clear() 
    txtBoxGrade6.Clear() 
    txtBoxGrade7.Clear() 
    txtBoxGrade8.Clear() 

    txtBoxTotalGPA.Clear() 
    txtBoxTotalHours.Clear() 
    txtBoxTotalQualityPoints.Clear() 

End Sub 

感謝您提供的任何幫助！

Answer 1

看看Int32.TryParse方法。它會嘗試解析數據，如果成功則返回一個值。

http://msdn.microsoft.com/en-us/library/f02979c7.aspx?cs-save-lang=1&cs-lang=vb#code-snippet-1