我如何解决'功能不会返回所有代码路径上的值'

Question

我已经研究和阅读了一切，我可以从这里的问题，但没有我已经尝试解决了这个问题。该函数旨在为应用程序输出一个字母等级。这里是类和函数的代码，以获得更好的清晰度。

Public Class Coursegrade 
'names private veriables 
Private _Score1 As Integer 
Private _Score2 As Integer 
Private _Score3 As Integer 
Private Letter_grade As String 
'gets and returns each veriable 
'for application use 
Public Property Grade As String 
    Get 
     Return Letter_grade 
    End Get 
    Set(value As String) 
     If value > String.Empty Then 
      Letter_grade = value 
     Else 
      Letter_grade = String.Empty 
     End If 
    End Set 
End Property 
Public Property TestScore1 As Integer 
    Get 
     Return _Score1 
    End Get 
    Set(value As Integer) 
     If value > 0 Then 
      _Score1 = value 
     Else 
      _Score1 = 0 
     End If 
    End Set 
End Property 


Property TestScore2 As Integer 
    Get 
     Return _Score2 
    End Get 
    Set(value As Integer) 
     If value > 0 Then 
      _Score2 = value 
     Else 
      _Score2 = 0 
     End If 
    End Set 
End Property 

Public Property TestScore3 As Integer 
    Get 
     Return _Score3 
    End Get 
    Set(value As Integer) 
     If value > 0 Then 
      _Score3 = value 
     Else 
      _Score3 = 0 
     End If 
    End Set 
End Property 

'starts veriables of at 0 
Public Sub New() 
    _Score1 = 0 
    _Score2 = 0 
    _Score3 = 0 
End Sub 
'calculates the adverage 
Public Function Gettotal() As Integer 
    Return _Score1 + _Score2 + _Score3 
End Function 


Public Function Give_letter_grade() As String 
    Dim intTotal As Integer 
    intTotal = Gettotal() 

    'start your secletion 
    If intTotal <= 270 AndAlso intTotal >= 300 Then 
     Letter_grade = "A" 
    ElseIf intTotal <= 240 AndAlso intTotal >= 269 Then 
     Letter_grade = "B" 
    ElseIf intTotal <= 210 AndAlso intTotal >= 239 Then 
     Letter_grade = "C" 
    ElseIf intTotal <= 180 AndAlso intTotal >= 290 Then 
     Letter_grade = "D" 
    ElseIf intTotal > 180 Then 
     Letter_grade = "F" 
    Else 

     Letter_grade = "" 
    End If 
End Function 

错误显示上给予字母等级

Answer 1

Public Function Give_letter_grade() As String 
Dim intTotal As Integer 
intTotal = Gettotal() 

'start your secletion 
If intTotal <= 300 AndAlso intTotal >= 270 Then 
    Letter_grade = "A" 
ElseIf intTotal <= 269 AndAlso intTotal >= 240 Then 
    Letter_grade = "B" 
ElseIf intTotal <= 239 AndAlso intTotal >= 210 Then 
    Letter_grade = "C" 
ElseIf intTotal < 210 AndAlso intTotal >= 180 Then 
    Letter_grade = "D" 
ElseIf intTotal < 180 Then 
    Letter_grade = "F" 
Else 

    Letter_grade = "" 
End If 

Return Letter_grade '<--- you are missing the 'Return' statement 
End Function