我不明白为什么会出现索引超出范围的在线错误：AssessmentRecord.ToList(RecordPosition).Exams = Val(txtscore.Text)

Question

进入连续评估的代码

Private Sub bnloadrecords_Click(sender As Object, e As EventArgs) 句柄 bnloadrecords.Click

    If cboclass.Text = "" Or cbostream.Text = "" Or cbosubject.Text = "" Then
    MsgBox("Please select a class, stream and subject to proceed!", MsgBoxStyle.Exclamation + MsgBoxStyle.OkOnly)
    Exit Sub
    End If

Dim db As New SMSDataContext
Dim AssessmentRecords = From p In db.Assessments



    Where p.Class = cboclass.Text And p.Stream = cbostream.Text And p.Subject = cbosubject.Text
    Select p
    If AssessmentRecords.Count <> 0 Then
    Me.AssessmentsTableAdapter.FillByClass(Me.SMS.Assessments, cboclass.Text, cbostream.Text, cbosubject.Text)

Else


Dim StudentRecords = From p In db.Students                            
Where p.Class = cboclass.Text And p.Stream = cbostream.Text
Select p



    If StudentRecords.Count = 0 Then
    MsgBox("No student' records in the system that match your criteria!", MsgBoxStyle.Exclamation + MsgBoxStyle.OkOnly)
    Exit Sub
    Else


    For j = 1 To StudentRecords.Count

Dim NewAssessmentRecord As New Assessment With {.CA = 0, .Class = cboclass.Text, .Full_Name = StudentRecords.ToList(j - 1).Full_Name, .Registration_Number = StudentRecords.ToList(j - 1).Registration_Number, .Stream = cbostream.Text, .Subject = cbosubject.Text}

db.Assessments.InsertOnSubmit(NewAssessmentRecord)
db.SubmitChanges()

Next


        Me.AssessmentsTableAdapter.FillByClass(Me.SMS.Assessments, cboclass.Text, cbostream.Text, cbosubject.Text)           
    lblcurrentStudent.Text = AssessmentRecords.FirstOrDefault.Full_Name
    RecordPosition = 0
    txtscore.Focus()
    End If
End If

End Sub

将 RecordPosition 调暗为整数

Private Sub bnenter_Click(sender As Object, e As EventArgs) 句柄 bnenter.Click

    If txtscore.Text = "" Then
    MsgBox("Continous Assessment cannot be empty!", MsgBoxStyle.Exclamation + MsgBoxStyle.OkOnly)
    Exit Sub
     End If

    If Not IsNumeric(txtscore.Text) Then
    MsgBox("Score must be numeric!", MsgBoxStyle.Exclamation + MsgBoxStyle.OkOnly)
    Exit Sub
    End If

    If Val(txtscore.Text) > 25 Then
    MsgBox("CA Score cannot be above 25 marks!", MsgBoxStyle.Exclamation + MsgBoxStyle.OkOnly)
    Exit Sub
    End If
Dim db As New SMSDataContext
Dim AssessmentRecord = From p In db.Assessments

    Where p.Class = cboclass.Text And p.Stream = cbostream.Text And p.Subject = cbosubject.Text
    Select p

    If RecordPosition < (AssessmentRecord.Count - 1) Then
    MsgBox("End of Records Reached!", MsgBoxStyle.Exclamation + MsgBoxStyle.OkOnly)
    Exit Sub
    End If

AssessmentRecord.ToList(RecordPosition).CA = Val(txtscore.Text)
db.SubmitChanges()
RecordPosition += 1

    If RecordPosition = (AssessmentRecord.Count - 1) Then
    MsgBox("End of Record Reached!", MsgBoxStyle.Exclamation +MsgBoxStyle.OkOnly)
    Exit Sub 
    End If

txtscore.Clear()
txtscore.Focus()
End Sub

进入考试代码

Private Sub bnloadrecords_Click(sender As Object, e As EventArgs) 句柄 bnloadrecords.Click

    If cboclass.Text = "" Or cbostream.Text = "" Or cbosubject.Text = "" Then
        MsgBox("Please select a class, stream and subject to proceed!",MsgBoxStyle.Exclamation + MsgBoxStyle.OkOnly)
    Exit Sub
    End If

Dim db As New SMSDataContext
Dim AssessmentRecords = From p In db.Assessments


    Where p.Class = cboclass.Text And p.Stream = cbostream.Text And p.Subject = cbosubject.Text
                       Select p



    If AssessmentRecords.Count <> 0 Then   Me.AssessmentsTableAdapter.FillByClass(Me.SMS.Assessments,cboclass.Text,cbostream.Text, cbosubject.Text)
     Else


Dim StudentRecords = From p In db.Students

 Where p.Class = cboclass.Text And p.Stream = cbostream.Text
                          Select p



    If StudentRecords.Count = 0 Then
        MsgBox("No student' records in the system that match your criteria!", MsgBoxStyle.Exclamation + MsgBoxStyle.OkOnly)
    Exit Sub
    Else


    For j = 1 To StudentRecords.Count

    Dim NewAssessmentRecord As New Assessment With {.Class = cboclass.Text, .Exams = 0, .Full_Name = StudentRecords.ToList(j - 1).Full_Name, .Registration_Number = StudentRecords.ToList(j - 1).Registration_Number, .Stream = cbostream.Text, .Subject = cbosubject.Text}

                            db.Assessments.InsertOnSubmit(NewAssessmentRecord)
                            db.SubmitChanges()


    Next
                    Me.AssessmentsTableAdapter.FillByClass(Me.SMS.Assessments, cboclass.Text, cbostream.Text, cbosubject.Text)        

 lblcurrentStudent.Text = AssessmentRecords.FirstOrDefault.Full_Name
 RecordPosition = 0
 txtscore.Focus()
End If     
End If
End Sub

将 RecordPosition 调暗为整数

Private Sub bnenter_Click(sender As Object, e As EventArgs) 句柄 bnenter.Click

    If txtscore.Text = "" Then
       MsgBox("Exams cannot be empty!", MsgBoxStyle.Exclamation +   MsgBoxStyle.OkOnly)
       Exit Sub
    End If


    If Not IsNumeric(txtscore.Text) Then
    MsgBox("Score must be numeric!", MsgBoxStyle.Exclamation + MsgBoxStyle.OkOnly)
    Exit Sub
    End If


    If Val(txtscore.Text) > 75 Then
    MsgBox("Exams Score cannot be above 75 marks!", MsgBoxStyle.Exclamation + MsgBoxStyle.OkOnly)
    Exit Sub
    End If

Dim db As New SMSDataContext
Dim AssessmentRecord = From p In db.Assessments

    Where p.Class = cboclass.Text And p.Stream = cbostream.Text And p.Subject = cbosubject.Text
    Select p

    If RecordPosition < (AssessmentRecord.Count - 1) Then
    MsgBox("End of Records Reached!", MsgBoxStyle.Exclamation + MsgBoxStyle.OkOnly)
    Exit Sub
    End If


AssessmentRecord.ToList(RecordPosition).Exams = Val(txtscore.Text)
db.SubmitChanges()
RecordPosition += 1

    If RecordPosition = (AssessmentRecord.Count - 1) Then
    MsgBox("End of Record Reached!", MsgBoxStyle.Exclamation + MsgBoxStyle.OkOnly)
    Exit Sub
    End If

txtscore.Clear()
txtscore.Focus()

结束子

计算连续评估和考试的代码

Private Sub bncomputeresults_Click(sender As Object, e As EventArgs) 句柄 bncomputeresults.Click

    If cboclass.Text = "" Or cbostream.Text = "" Then
    MsgBox("Select a class and stream to proceed!", MsgBoxStyle.Exclamation + MsgBoxStyle.OkOnly)
    Exit Sub
    End If



Dim db As New SMSDataContext
Dim AssessmentRecords = From p In db.Assessments

    Where p.Class = cboclass.Text And p.Stream = cbostream.Text
    Select p



    If AssessmentRecords.Count = 0 Then
    MsgBox("No records found, Please select a new set of options to proceed!", MsgBoxStyle.Exclamation + MsgBoxStyle.OkOnly)
    Exit Sub
    End If



    For j = 1 To AssessmentRecords.Count
    AssessmentRecords.ToList(j - 1).Exams = Val(AssessmentRecords.ToList(j - 1).CA) + Val(AssessmentRecords.ToList(j - 1).Exams)


    If Val(AssessmentRecords.ToList(j - 1).Exams) >= 80 Then
    AssessmentRecords.ToList(j - 1).Grade = "1"
    AssessmentRecords.ToList(j - 1).Remarks = "DISTINCTION"


    ElseIf Val(AssessmentRecords.ToList(j - 1).Exams) >= 79 Then
    AssessmentRecords.ToList(j - 1).Grade = "2"
    AssessmentRecords.ToList(j - 1).Remarks = "MERIT"


    ElseIf Val(AssessmentRecords.ToList(j - 1).Exams) >= 69 Then
    AssessmentRecords.ToList(j - 1).Grade = "3"
    AssessmentRecords.ToList(j - 1).Remarks = "CREDIT"


    ElseIf Val(AssessmentRecords.ToList(j - 1).Exams) >= 59 Then
    AssessmentRecords.ToList(j - 1).Grade = "4"
    AssessmentRecords.ToList(j - 1).Remarks = "PASS"
Else

    AssessmentRecords.ToList(j - 1).Grade = "F"
    AssessmentRecords.ToList(j - 1).Remarks = "FAIL"
    End If

Next


db.SubmitChanges()
Dim TotaledRecords = From p In db.Assessments    

    Where p.Class = cboclass.Text And p.Stream = cbostream.Text
    Select p
    Order By p.Total Descending





    For j = 1 To TotaledRecords.Count
     TotaledRecords.ToList(j - 1).Position = j

 Next


db.SubmitChanges()
Me.AssessmentsTableAdapter.FillByClassStream(Me.SMS.Assessments, cboclass.Text, cbostream.Text)

End Sub

Answer 1

我怀疑他的块是为了防止 RecordPosition 成为无效索引，但它恰恰相反。

If RecordPosition < (AssessmentRecord.Count - 1) Then
    MsgBox("End of Records Reached!", MsgBoxStyle.Exclamation + MsgBoxStyle.OkOnly)
    Exit Sub
End If

第一行可能应该使用 > 而不是 < 以便在 RecordPosition 超过列表末尾时停止。

If RecordPosition > (AssessmentRecord.Count - 1) Then

我不明白为什么会出现索引超出范围的在线错误：AssessmentRecord.ToList(RecordPosition).Exams = Val(txtscore.Text)

I don' t understand why am getting an index out of range error on line: AssessmentRecord.ToList(RecordPosition).Exams = Val(txtscore.Text)

vb.net-2010